QBASIC with an Introduction to Visual Basic for Engineering, Mathematics, and the Sciences [2 ed.] 0024076112, 9780024076113

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QBASIC WITH AN INTRODUCTION TO VISUAL BASIC FOR ENGINEERING, MATHEMATICS, AND THE SCIENCES

Invoking QBasic 1. From DOS, type QBASIC and press the Enter key.

Some Common QBasic Commands (key1+key2 means “Hold down key! while pressing key2.”) (key1/key2 means “Release key1 before pressing key2.”) cursor between View window and Menu bar program from disk into the View window new program in the View window copy of the current program between View window and Output screen

Alt Alt/File/Open Alt/File/New Alt/File/Print/Enter F4

Toggle Place a Start a Print a Toggle

Esc

Remove a menu, dialog box, or help box

Shift+F5 Alt/File/Save As Alt/File/Exit

Run the the current program. Denoted: [run] Save the current program Exit QBasic and return to DOS

Cul+Y Shift+Ins Home End Cul+Home Ctrl+End

Delete Insert Move Move Move Move

Home/Ctrl+N End/Enter

Insert line above current line with cursor on new line Insert line below current line with cursor on new line

Help

Fl Shift+F1 Esc

Get information about word at cursor Get help on “Help” Remove help box

Dialog Box

Tab Esc

Move around in a dialog box Remove a dialog box

Environment

Cursor Moving

line containing cursor and place in clipboard contents of clipboard at cursor to beginning of line containing cursor to end of line containing cursor to beginning of program to end of program

Procedures To open a window for a subprogram, enter the keyword SUB’ followed by anes The name can be followed by parameters, if desired’. ge

SUB Name FUNCTION

Name

of the subprogram.

To open a window for a function, enter the keyword FUNCTION ilove by the name of the function. The name can be followed by parameters, if desired.

Shift+F2

Cycle through the procedures (in alphabetical order) and the main body of the program.

ey

Display a list beginning with the program name and containing the names of the procedures. Use the cursor-moving keys and the Enter key to make a selection.

F2/(Sel)/Tab/Del/Enter

To delete a procedure, press F2, select the procedure to be deleted, and then press Tab/D/Enter.

Obtaining a Printed Copy of the QBasic Program Output 1. Check that the printer is turned on, has paper, and is “on line.” 2. Run the program and then press F4 twice to display the desired output on the Output screen with “Press any key to continue” removed. 3. Press Shift+Print Screen.

Note: If the program uses graphics mode, consult Chapter 10.1 on the use of GRAPHICS.COM.

Obtaining Graphics from QBasic with a Hercules Adapter and Monochrome Monitor 1. Enter MSHERC before invoking QBasic from DOS. 2. Use SCREEN 3 instead of SCREEN 2 in programs.

This book contains a diskette, the use of which is governed by a break-the-seal Microsoft Software License on the last page of the book.

QOBASIC™ With an Introduction to

Visual Basic for Engineering, Mathematics, and the Sciences Second Edition

David I. Schneider roe

University of Maryland

DECLEN an imprint of

MACMILLAN

COLLEGE PUBLISHING COMPANY, New York

MAXWELL MACMILLAN

CANADA, Toronto

MAXWELL MACMILLAN INTERNATIONAL New York Oxford Singapore Sydney

On the Cover: Veazy (1990) is an unusual, round painting by New York artist Gary Lang. It is acrylic on canvas and measures 27 inches in diameter. Lang’s use of vibrant colors and intentional irregularities in the painted surface create a dazzling visual display. Lang received a Master of Fine Arts degree from Yale University in 1975 and has been the focus of numerous one-man exhibitions throughout the United States and Europe. His work is included in the permanent collections of the Whitney Museum of American Arts, New York; the Museum of Contemporary Art, Los Angeles; the Madison Art Center, Wisconsin; and the Menil Collection, Houston, Texas. He is represented by Brian Gross Fine Art, San Francisco, and Michael Klein, Inc., New York City.

Photography:

John Drooyan

Interior Design and Composition:

Rebecca Evans

& Associates

Photo/Illustration Credits: page 311, Courtesy of Hammond Incorporated; Incorporated; page 436, Courtesy of Resorts International Hotel Casino.

page 444, Courtesy of Hammond

© Copyright 1994 by Macmillan College Publishing Company, Inc. Dellen is an imprint of Macmillan College Publishing Company. Printed in the United States of America.

IBM is a registered trademark of International Business Machines Corporation. Hercules is a trademark of Hercules Computer Technology. Microsoft is a registered trademark of Microsoft Corporation.

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the Publisher. Macmillan College Publishing Company 866 Third Avenue New York, NY 10022

Macmillan College Publishing Company is part of the Maxwell Communication Group of Companies. Maxwell Macmillan Canada, Inc.

1200 Eglinton Avenue East, Suite 200 Don Mills, Ontario M3C 3N1

Library of Congress Cataloging in Publication Data Schneider, David I.

QBASIC: with an introduction to Visual Basic for engineering, mathematics, and the sciences / David I. Schneider — 2nd ed.

paeem: Rev. ed. of: Microsoft QBASIC. 1991. Includes index. ISBN 0-02-40761 1-2 1. QBasic (Computer program language). 2. Microsoft QuickBASIC. 3. Microsoft Visual BASIC. I. Schneider, David I. II. Title. QA76.73.Q33S37 1994 005.26’2—dc20 94-9640 CIP ISBN 0-02—40761 1-2 Ponting:

2

394556

Year:

984516

Contents Preface vi Acknowledgments

Chapter 1

An Introduction to Computers and QBasic 1.1 1.2 1.3. 1.4

Chapter 2

An Introduction to Computers 2 Getting Started 4 Using Diskettes and DOS 15 Biographical History of Computing

Program Development Cycle Programming Tools 30

Vil 28

Fundamentals of QBasic 3.1 Numbers 40 372) Strings, 33 3.3 DataInput 63 3.4 Numeric Functions 78 3.5. Screen Placement and Formatting Summary 104 Programming Projects 105

Chapter 4

bbe)

92

ial

Decisions

4.1 Relational and Logical Operators 4.2 IFBlocks 117 4.3 SELECT CASE Blocks 132 Summary 147 Programming Projects 147

Chapter 5

22

Problem Solving 2.1 2.2

Chapter 3

ix

112

Repetition 5.1 DOLoops 152 5.2 Processing Lists of Data with DO Loops 5.3. FOR...NEXT Loops 185 Summary 200 Programming Projects 201

Chapter 6

151 167

207

Procedures

6.1 Subprograms, Part] 208 6.2 Subprograms, Part I] 227 6.3 Functions 242 6.4 Modular Design 254 6.5 A Case Study: Numerical Integration Summary 267 Programming Projects 267

259

iii

iv

Contents

Chapter 7

agit

Arrays 7.1 Creating and Accessing Arrays 272 7.2 Using Arrays 287 7.3. Sorting and Searching 305 7.4 Two-Dimensional Arrays 323 7.5 A Case Study: Calculating with a Spreadsheet Summary 345 Programming Projects 346

Chapter 8

337

355

Sequential Files 8.1 Sequential Files 356 8.2 Using Sequential Files 368 8.3 A Case Study: Creating a Receipt 377 Appendix: Displaying the Contents of a File 381 Summary 382 Programming Projects 382

Chapter 9

389

Random-Access Files 9.1 DataTypes 390 9.2 Random-Access Files 399 Summary 405 Programming Projects 405

Chapter 10

Graphics

407

10.1 Introduction to Graphics 408 10.2 Specifying a Coordinate System 409 10.3 Drawing Graphs of Functions 418 Summary 425 Programming Projects 426

Chapter 11

11.1 Generating Random Numbers 11.2 Games of Chance 436 11.3 Monte Carlo Methods 446 Summary 454 Programming Projects 455

Chapter 12

427

Random Numbers

428

Visual Basic

12.1 An Introduction to Visual Basic 458 12.2 Visual Basic Objects 461 12.3 Visual Basic Events 471 12.4 Converting QBasic Programs to Visual Basic 485 12.5 A Case Study: Recording Checks and Deposits 502 Summary 511 Programming Projects 512

457

Contents

Appendixes

v

515 Appendix A. Appendix B. Appendix C. Appendix Appendix Appendix Appendix Appendix Appendix

D. E. F. G. H. I.

Appendix J.

ASCII Values 515 Usinga Mouse 517 QBasic Statements, Functions, Operators, and Metacommands 520 QBasic Debugging Tools 550 A Summary of QBasic Editing Commands 558 The QBasic Environment 560 HOW TO (QBasic) 566 An Introduction to Windows 575 HOW TO (Visual Basic) 584 Visual Basic Statements, Events, Functions, Methods, Properties, Data Types, and Operators 597

Answers to Selected Odd-Numbered Exercises

621

Index

667

Index of Selected Engineering, Mathematics, and Science Applications

673

Preface This text presents the fundamentals of programming in Microsoft® QBasic™ on IBM PC compatible computers and an introduction to Microsoft® Visual Basic™. My objectives when writing this text were as follows: 1. To develop focused chapters. Rather than covering many topics superficially, I concentrate on important subjects and cover them thoroughly. 2. To use examples and exercises with which students can relate, appreciate, and feel comfortable. I frequently use real data. Examples do not have so many embellishments that students are distracted from the programming techniques illustrated. 3. To produce compactly written text that students will find both readable and informative. The main points of each topic are discussed first and then the peripheral details are presented as comments.

4. To teach good programming practices that are in step with modern programming methodology. Problem solving techniques and structured programming are discussed early and used throughout the book. 5. To provide insights into the major applications of computers, with special emphasis on engineering, mathematics, and the sciences.

Unique and Distinguishing Features Exercises for Most Sections. Each section that teaches programming has an exercise set. The exercises both reinforce the understanding of the key ideas of the section and challenge the student to explore applications. Most of the exercise sets require the student to trace programs, find errors, and write programs. The answers to most of the odd-numbered exercises in Chapters 2 through 8 and selected odd-numbered exercises from Chapters 9 through 12 are given at the end of the text.

Practice Problems. Practice problems are carefully selected exercises located at the end of a section, just before the exercise set. Complete solutions are given following the exercise set. The practice problems often focus on points that are potentially confusing or are best appreciated after the student has worked on them. The reader should seriously attempt the practice problems and study their solutions before moving on to the exercises. Programming Projects. Beginning with Chapter 3, every chapter contains programming projects. The programming projects not only reflect the variety of ways that computers are used in the business and engineering communities, but also present some games and general interest topics. The large number and range of difficulty of the programming projects provide the flexibility to adapt the course to the interests and abilities of the students. Some programming projects in Chapters 7 through 12 can be assigned as end-of-the-semester projects.

vi

Preface

Comments.

vii

Extensions and fine points of new topics are reserved for the

“Comments” portion at the end of each section so that they will not interfere with the flow of the presentation. Case Studies.

Each of the four case studies focuses on an important program-

ming application. The problems are analyzed and the programs are developed with top-down charts and pseudocode. The programs can be found in the EXAMPLES directory of the enclosed diskette. Chapter Summaries. In Chapters 3 through 12, the key results are stated and the important terms are highlighted. Strings Used Throughout Text. The introduction of strings in Chapter 3 and their regular use from then on prepare the student for substantial string-handling

programs. Procedures.

Procedures

are introduced

after decision structures and

loops.

However, Section 6.1 and most of Section 6.2 can be covered after Chapter 3

for those instructors who prefer an early introduction to procedures. Arrays. Arrays are introduced gently in two sections. The first section presents the basic definitions and avoids procedures. The second section presents the techniques for manipulating arrays and shows how to pass arrays to procedures. Appendix on Debugging. The placement of the discussion of QBasic’s sophisticated debugger in an appendix allows the instructor flexibility in deciding when to cover this topic. Reference Appendices. Appendices serve as a compact reference manual for the environments and statements of both QBasic and Visual Basic.

Instructors Solution Diskette. A diskette containing the solution to every exercise and programming project is available for the instructor. Examples,

Case Studies, and Visual Basic Diskette.

Each book contains a

diskette holding all the examples and case studies from this text and also a copy of the Primer Edition of Visual Basic 2.0.

What’s New in the Second Edition

1. Suggestions from students and reviewers of the book have been incorporated as much as possible.

2. The real-life data in the examples and exercises have been updated and revised. 3. The chapter on graphics has been modernized to apply to VGA monitors. 4. The functions VAL and STR$ have been added to the section on built-in functions.

5. The section on DOS has been revised with the assumption that the computer has a hard disk.

6. A discussion of QBasic’s operators has been added to Appendix C.

Viii

Preface

7. The main change is adding an introduction to Visual Basic for Windows— the state of the art in Basic programming. Since Visual Basic uses essentially the same programming constructs as QBasic, students can leverage their knowledge of QBasic and make themselves much more marketable for the 90’s. (Knowledge of Visual Basic makes someone more marketable because its extraordinary combination of power and ease of use has made Visual Basic the tool of choice for developing user-friendly applications in the business world. In addition, Microsoft has made Visual Basic the language used to take full control of its best selling Windows applications such as Microsoft Word or Microsoft Excel.)

There’s one more point that shouldn’t be underestimated—Visual Basic is fun! Learning Visual Basic was very exciting to me—most students have similar reactions when they see how easy it is to build powerful visual interfaces using it. The chapter on Visual Basic can be used in several ways. (a) The chapter can be covered in detail. (b) The instructor can give a survey of the language in one or two lectures. (c) The chapter can be assigned as an optional enrichment topic.

Whether or not the chapter is covered in class, I encourage all students to learn about Visual Basic, the language Microsoft chairman Bill Gates describes as “the programming language for the 90’s.”

Acknowledgments Many talented instructors, students, and programmers provided helpful com-

ments and thoughtful suggestions at each stage in the preparation of this text. | extend my gratitude for their contributions to the quality of the book to Shakil

Akhtar, Central Michigan University; William A. Bailey, Jr., University of North Carolina at Charlotte; Abdel Fatah Bashir, Moorhead State University;

Curtis Bring, Moorhead

State University; John Caldwell, College of Lake

County; Gene B. Chase, Messiah College; Curtis Childress, Rancho Santiago College; Michael Cooper, University of California at Berkeley; Noel Dahlen,

Rancho Santiago College; Louise Darcy, Texas A&M

University; Mark Ellis,

MIT; Richard Fedder, Grand Valley State University; Ronald D. Ferguson, San

Antonio

College; W. Fred Fry, Rancho

Santiago College; Kevin Gorman,

University of North Carolina at Charlotte; Samuel Graff, John Jay College of Criminal Justice; Bill Higgins, Messiah College; Bill Hoffman, Cogswell Polytech College; Milo Johnson, College of the Redwoods; Monte Johnson,

St. Cloud State University; Dee Joseph, San Antonio College; James P. Kelsh, Central Michigan University; Suban Krishnamoorthy, Framingham State College; Shelly Langman; Norman Lindquist, W. Washington University; Jackie Lou, Montgomery College; Lewis D. Miller, Canada College; Calvin Mittman, St. Johns University; Barry Parris, University of South Carolina at Spartanburg; Juanita J. Peterson, College of Alameda; James T. Ramey, Jr., Francis Marion College; John Repede,

University of North Carolina at Charlotte;

Peter Rosenbaum,

Framingham State College; R. Waldo Roth, Tulsa Research Center; Barbara Saxton, Lehigh County Community College; Sandra M. Schleiffers, Colorado State University; Y. Sitaraman, Kentucky Wesleyan College; Phil Steitz, Beloit College; Brooke Stephens, University of Maryland; Bill Strausbaugh, Messiah College; Brian Turnquist, University of Maryland; Michael Willis, Montgomery College; Charles M. Williams, Georgia State University; Sheryl Barricklow,

Grand Valley State University; Joseph Farrelly, Palomar College; Raymond Fadous, University of Michigan at Flint; Francis A. Greene, Essex Community College; Patricia A. Joseph, Slippery Rock University of Pennsylvania; Andy Lau,

Pennsylvania

State at Harrisburg;

Glen

Lobo,

Ferris State University;

Robert Spear, Prince George’s Community College; William A. Moy, University of Wisconsin-Parkside; Andrew McConnell, Napa Valley College; Rita Mudd, Inver Hills Community College; Ernst Rilki, Harper College; Ronald W. Surprenant, Suffolk County Community College; Thomas P. Wiggen, University of North Dakota John Drooyan contributed creative photographs and artwork, Rebecca Evans & Associates used state-of-the-art technology to compose the text. I extend an extra special thanks to Don Dellen, president of Dellen Publish-

ing Company, for his help in planning and executing this text. His partnership and friendship have added a warm personal dimension to the writing process. Last, but not least,

| am grateful to the Microsoft Corporation for their

commitment to producing outstanding programming languages and for their permission to include a copy of the Primer Edition of Visual Basic with each book.

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An Introduction to Computers and QBasic ATAVVES,

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appears and the C drive is the default drive. To change the default drive to B, enter B:. The prompt will change to B>. Files and Directories

Disks hold not only programs but also collections of data stored in data files. The term file refers to either a program or a data file. In Section 1.2 we created a program file. Chapters 8 and 9 are devoted to data files. Each file has a name consisting of a base name of at most eight characters followed by an optional extension consisting of a period and at most three characters. Letters, digits, and a few other assorted characters (see Comment

1) can be used in either the base

name or the extension. Blank spaces are not allowed. Some examples of file names are INCOME.94, CUSTOMER.DAT,

and FORT500.

Since a disk is capable of storing thousands of files, locating a specific file can be quite time consuming. Therefore, DOS allows related files to be grouped into directories. Think of a disk as a large envelope, called the root envelope, which contains several smaller envelopes, each with its own name. (The naming of envelopes follows the same rule as the naming of files.) Each of these smaller envelopes can contain yet other named envelopes. Each envelope is identified by listing it preceded by the successively larger envelopes that contain it, with each envelope name preceded by a backslash. Such a sequence is called a path. For instance, the path \SALES\NY.90\JULY identifies the envelope JULY, contained in the envelope NY.90, which in turn is contained in the envelope SALES. Think of a file name as written on a slip of paper that can be placed into either the root envelope or any of the smaller envelopes. At any time, we can select one of the envelopes. The selected envelope is called the current envelope. All commands to place a slip of paper into an envelope or list the contents of an envelope refer to the current envelope unless a path leading to another envelope is specified. In the language of directories, the root envelope is the root directory, the other envelopes are subdirectories, and the current envelope is the current directory. When DOS is first invoked, the root directory of the current drive is the current directory. The command CD pathName

18

An Introduction to Computers and QBasic

tells DOS to change the current directory to the directory at the end of the named path. The command CD \

makes the root directory the current directory. The command MD directoryName

tells DOS to create a new subdirectory with the specified name in the current directory of the current drive. The command RD directoryName

tells DOS to remove the specified subdirectory from the current directory of the current drive. A subdirectory can be removed only if it has no files or subdirectories. The current directory cannot be removed. The combination of a drive letter followed by a colon, a path, anda file name is called a filespec, an abbreviation of “file specification.” Some examples of filespecs are C:\ DOS\QBASIC.EXE and A:\PERSONAL \ INCOME94.DAT. If the drive (along with the colon) or the path is omitted, then the file is assumed to reside in the current drive or the current directory, respectively. Other DOS Commands Some other commands that can be executed in DOS are FORMAT, DIR, COPY, ERASE, and RENAME.

FORMAT The first time a blank diskette is used, it must be formatted for the computer. The formatting process is analogous to preparing graph paper by drawing grid lines. Let’s assume the unformatted diskette is in the A drive, and the current drive is C. To format the diskette, enter FORMAT

A:

and then follow the directions displayed on the screen. While the formatting is taking place, the light on the A drive will be on, the blank diskette will spin, and the percentage of the diskette formatted will be displayed. After about one minute, the message “Format complete” will appear on the screen, and you will be prompted for a volume label. A volume label is a name (consisting of 1 to 11 characters) for your diskette. You can decline to specify a volume label by pressing the Enter key. You will be informed of the amount of space on the diskette, and the statement “Format another (Y/N)?” will be displayed. Answer

the question by pressing either the Y or N key and then the Enter key. If the answer is N, the DOS prompt will appear and await your next command. If the answer is Y, the steps above will be repeated.

1.3

USING DISKETTES AND DOS

19

Caution: Formatting any disk destroys all its existing files. The hard disk is formatted when the computer is first readied for use, so never enter FORMAT C:.

DIR The command DIR

displays the names of the files and subdirectories in the current directory. (Periods are omitted and the base names are separated from the extensions.)

If the disk has more than a screenful of files, enter the command

DIR /P which makes the computer display just a screenful of files at a time. The command DIR

*.BAS

displays only files with the extension BAS. To generalize, the command DIR

*.ext

displays only files with the specified extension and the command DIR

baseName .*

displays only files with the specified base name.

COPY The command COPY is used to make a second copy of a file. The command COPY filespec

A:

copies the specified file to the current directory of the diskette in drive A. In general, the command COPY filespec

driveLetter:

copies the specified file to the current directory of the disk in drive driveLetter.

ERASE The command ERASE filespec

removes the specified file from the disk. For instance, the command ERASE B:\ ACCOUNTS.BAS deletes the file ACCOUNTS.BAS from the root direc-

tory of the diskette in drive B.

20

An Introduction to Computers and QBasic

RENAME The command filenamel

RENAME

filename2

changes the name of the file identified as filename! to the new name filename2. The new name must be different from the name of any file in the current directory. Comments:

i File names can consist of digits, letters of the alphabet, and the characters &!_ @’‘~(){}-#% $. Spaces are not allowed in file names.

. Neither DOS nor QBasic distinguishes between upper and lowercase letters in file names. For instance, the names COSTS89.BAS,

Costs89.Bas, and

costs89.bas are equivalent. DOS always displays file names with uppercase characters. . The asterisk used with the DIR command is called a wildcard character. It

also can be used with COPY or ERASE to apply the command to many files at once. For instance, COPY *.BAS A: copies files with extension .BAS to the A drive, ERASE TEMP.* erases files with base name TEMP, and COPY

* * B: copies all files in the current directory of the current drive to drive B. . The QBasic command NAME can be used in a program to change the file name of any file on any disk. The statement NAME

"filenamel"

AS

"filename2"

has the same effect as the corresponding DOS command RENAME. Note that with the NAME command, filename! and filename2 must each be surrounded by quotation marks. . The QBasic command KI

filespec™

can be used in a program and has the same effect as the DOS command ERASE. Note that with the KILL command, filespec must be surrounded by quotation marks. . If the name of a QBasic program is not given an extension when saved, QBasic automatically gives it the extension .BAS. This extension can be omitted when opening the program with Alt/F/O, but must be used when deleting or renaming the program.

. The QBasic environment provides a list of the programs on a disk at appropriate times. For instance, pressing Alt/F/O to open a program produces a dialog box similar to the one in Figure 1.9. The file to be retrieved from the disk can either be typed into the narrow rectangle at the top or selected from the list of QBasic programs in the lower rectangle. To make a selection from the listed programs, press Tab to move to the lower rectangle, use the cursor-moving keys to highlight the desired program, and then press the Enter key. With a mouse, you can select a program by double-clicking on it.

21

USING DISKETTES*AND DOS”

1.3

Open

File Nane:

|

Fe-sas

C:NQBASIC Dirs/Dr ives

Files

CASTLE. BAS CATAPULT.BAS EVALUATE.BAS GRAPH. BAS HUNTER. BAS MONEY. BAS NIBBLES. BAS ONE. BAS

PHONE . BAS RENLINE.BAS REVERSI .BAS SORTDEMO .BAS SUBS_EX. BAS

< Cancel

Figure 1.9

>

Dialog Box for Opening a File

PRACTICE PROBLEMS

1.3

1. The commands KILL “OPUS.1” and ERASE OPUS.1 both remove the file named OPUS.1 from a disk. What is the criterion for deciding when a file name must be enclosed by quotes?

Ze Suppose you have saved a QBasic program with the name MYPROG on drive B and you now want to erase the program from the disk. You execute the command KILL “B:MYPROG?” from a QBasic program and receive the error message “File not found.” What happened?

EXERCISES

1.3

In Exercises 1 through 9, give the DOS command that accomplishes the stated task. L Reproduce a file on another disk.

. Change the name of a file.

. Prepare a new diskette for use. . List the files in the current directory.

. Change the current disk drive to drive B.

toe)

. Create a new subdirectory of the current directory. . Change the current directory.

Noy

Sow

SS

. Delete a file from a disk.

. Remove a subdirectory of the current directory.

22

An Introduction to Computers and QBasic

In Exercises stated task.

10 and 11, give the QBasic command

that accomplishes the

10. Delete a program from a disk. 11. Change the name of a program.

the use you d coul How e. driv ette disk one just has er put com your e pos Sup 12. commands discussed in this section to copy all the files in the root directory of a diskette onto another diskette? SOLUTIONS TO PRACTICE PROBLEMS

1.3

1. The criterion is the “environment” that the user is in. File names used in QBasic programs must always be enclosed in quotes. File names used in DOS are never enclosed in quotes.

2. Since an extension was not specified when the program was saved, QBasic added the extension BAS. The proper command to erase the program is KILL “B:MYPROG.BAS”.

1

4 BIOGRAPHICAL HISTORY OF COMPUTING The following people made important contributions to the evolution of the computer and the principles of programming.

1800s George Boole: a self-taught British mathematician; devised an algebra of logic that later became a key tool in computer design. The logical operators presented in Section 4.1 are also known as Boolean operators. Charles Babbage: a British mathematician and engineer; regarded as the father of the computer. Although the mechanical “analytical engine” that he conceived was never built, it influenced the design of modern computers. It had units for input, output, memory, arithmetic, logic, and control. Algorithms were

intended to be communicated to the computer via punched cards, and numbers were to be stored on toothed wheels. Augusta Ada Byron: a mathematician and colleague of Charles Babbage; regarded as the first computer programmer. She encouraged Babbage to modify the design based on programming considerations. Together they developed the concepts of decision structures, loops, and a library of procedures. Decision structures, loops, and procedures are presented in Chapters 4, 5, and 6 of this text respectively.

Herman Hollerith: the founder of a company that was later to become IBM; at the age of 20 he devised a computer that made it possible to process the data for the U.S. Census of 1890 in one-third the time required for the 1880 census. His electromagnetic “tabulating machine” passed metal pins through holes in punched cards and into mercury-filled cups to complete an electronic circuit. Each location of a hole corresponded to a characteristic of the population.

1.4

BIOGRAPHICAL HISTORY OF COMPUTING = 23

1930s Alan Turing: a gifted and far-sighted British mathematician; made fundamental contributions to the theory of computer science, assisted in the construction of some of the early large computers, and proposed a test for detecting intelligence

within a machine. His theoretical “Turing machine” laid the foundation for the development of general purpose programmable computers. He changed the course of the second world war by breaking the German “Enigma” code, thereby making secret German messages comprehensible to the Allies.

John V. Atanasoff: a mathematician and physicist at lowa State University; declared by a federal court in Minnesota to be the inventor of the first electronic digital special-purpose computer. Designed with the assistance of his graduate assistant, Clifford Berry, this computer used vacuum tubes (instead of the less

efficient relays) for storage and arithmetic functions. 1940s

Howard Aiken: a professor at Harvard University; built the Mark I, a large- scale digital computer functionally similar to the “analytical engine” proposed by Babbage. This computer, which took five years to build and used relays for storage and computations, was technologically obsolete before it was completed. Grace M. Hopper: retired in 1986 at the age of 79 as a rear admiral in the United States Navy; wrote the first major subroutine (a procedure used to calculate sin x on the Mark I computer) and one of the first assembly languages. In 1945 she found that a moth fused into a wire of the Mark I was causing the computer to malfunction, thus the origin of the term “debugging” for finding errors. As an administrator at Remington Rand in the 1950s, Dr. Hopper pioneered the development and use of COBOL, a programming language for the business community written in English-like notation. John Mauchley and J. Presper Eckert: electrical engineers working at the University of Pennsylvania; built the first large-scale electronic digital generalpurpose computer to be put into full operation. The ENIAC used 18,000 vacuum tubes for storage and arithmetic computations, weighed 30 tons, and occupied 1500 square feet. It could perform 300 multiplications of 2 10-digit numbers per second, whereas the Mark I required 3 seconds to perform a single multiplication. Later they designed and developed the UNIVAC I, the first commercial electronic computer.

John von Neumann: a mathematical genius and member of the Institute of Advanced Studies in Princeton, New Jersey; developed the stored program

concept used in all modern computers. Prior to this development, instructions were programmed into computers by manually rewiring connections. Along with Hermann H. Goldstein, he wrote the first paper on the use of flowcharts. Stanislaw Ulam: Americar research mathematician and educator; pioneered the application of random numbers and computers to the solution of problems in mathematics and physics. His techniques, known as Monte Carlo methods or computer simulation, are used in Chapter 11 to determine the likelihoods of various outcomes of games of chance and to analyze business operations.

24

An Introduction to Computers and QBasic

Maurice V. Wilkes: an electrical engineer at Cambridge University in England the use to er put com first the AC, EDS the t buil n; man Neu von of ent stud and stored program concept. Along with D.J. Wheeler, and S. Gill, he wrote the first

computer programming text, The Preparation of Programs for an Electronic Digital and use the with th dep in t deal ch whi ), 1951 , ley Wes ondis (Ad er put Com construction of a versatile subroutine library. John Bardeen, Walter Brattain, and William Shockley: physicists at Bell Labs; developed the transistor, a miniature device that replaced the vacuum tube and revolutionized computer design. It was smaller, lighter, more reliable, and cooler than the vacuum tube. 1950s

John Backus: a programmer for IBM; in 1953 headed a small group of programmers who wrote the most extensively used early interpretive computer system, the IBM 701 Speedcoding System. An interpreter translates a high-level lan-

guage program into machine language one statement at a time as the program is executed. In 1957, Backus and his team produced the compiled language Fortran, which soon became the primary academic and scientific language. A compiler translates an entire program into efficient machine language before the program is executed. QBasic combines the best of both worlds. It has the power and speed of a compiled language and the ease of use of an interpreted language. Donald L. Shell in 1959, the year that he received his Ph.D. in mathematics from the University of Cincinnati, published an efficient algorithm for ordering (or sorting) lists of data. Sorting has been estimated to consume nearly one-quarter of the running time of computers. The Shell sort is presented in Chapter 7 of this text.

1960s John G. Kemeny and Thomas E. Kurtz: professors of mathematics at Dartmouth College and the inventors of BASIC; led Dartmouth to national leadership in the educational uses of computing. Kemeny’s distinguished career included serving as an assistant to both John von Neumann and Albert Einstein, serving as president of Dartmouth College, and chairing the commission to investigate the Three Mile Island accident. In recent years, Kemeny and Kurtz have devoted considerable energy to the promotion of structured BASIC. Corrado Bohm and Guiseppe Jacopini: two European mathematicians; proved that any program can be written with the three structures discussed in Section 2.2: sequences, decisions, and loops. This result led to the systematic methods of modern program design known as structured programming.

Edsger W. Dijkstra: professor of computer science at the Technological University at Eindhoven, The Netherlands; stimulated the move to structured programming with the publication of a widely read article, “Go To Statement Considered Harmful.” In that article he proposes that GOTO statements be abolished from all high-level languages such as BASIC. The modern programming structures available in QBasic do away with the need for GOTO statements.

1.4

Harlan B. Mills: IBM

BIOGRAPHICAL HISTORY OF COMPUTING

Fellow and Professor of Computer

25

Science at the

University of Maryland; has long advocated the use of structured programming.

In 1969, Mills was asked to write a program creating an information database for the New York Times, a project that was estimated to require thirty man- years with traditional programming techniques. Using structured programming techniques, Mills single-handedly completed the project in six months. The methods of structured programming are used throughout this text.

Donald E. Knuth: Professor of Computer Science at Stanford University; is generally regarded as the preeminent scholar of computer science in the world. He is best known for his monumental series of books, The Art of Computer Programming, the definitive work on algorithms. The algorithm presented in Exercise 27 of Section 11.1 of this text is an example of the programming gems appearing in Knuth’s books. Ted Hoff, Stan Mazer, Robert Noyce, and Federico Faggin: engineers Intel Corporation; developed the first microprocessor chip. Such chips, serve as the central processing units for microcomputers, are responsible extraordinary reduction in the size of computers. A computer with greater than the ENIAC can now be held in the palm of the hand.

at the which for the power

1970s Paul Allen and Bill Gates: co-founders of Microsoft Corporation; developed languages and the operating system for the IBM PC. The operating system, known as MS-DOS, is a collection of programs that manage the operation of the computer. In 1974, Gates dropped out of Harvard after one year, and Allen left a programming job with Honeywell to write software together. Their initial project was a version of BASIC for the Altair, the first microcomputer. Microsoft is one of the most highly respected software companies in the United States and a leader in the development of programming languages. Stephen Wozniak and Stephen Jobs: co-founders of Apple Computer Inc.; started the microcomputer revolution. The two had met as teenagers while working summers at Hewlett-Packard. Another summer, Jobs worked in an orchard, a job that inspired the names of their computers. Wozniak designed the Apple computer in Jobs’ parents’ garage and Jobs promoted it so successfully that the company was worth hundreds of millions of dollars when it went public. Both men resigned from the company in 1985. Dan Bricklin and Dan Fylstra: co-founders of Software Arts; wrote VisiCalc, the first electronic spreadsheet program. An electronic spreadsheet is a worksheet divided into rows and columns, which analysts use to construct budgets

and estimate costs. A change made in one number results in the updating of all numbers derived from it. For instance, changing a person’s housing expenses will immediately produce a change in his total expenses. Bricklin got the idea for an electronic spreadsheet after watching one of his professors at the Harvard Business School struggle while updating a spreadsheet at the blackboard. VisiCalc became so popular that many people bought personal computers just so they could run the program. A simplified spreadsheet is developed as a case study in Section 7.5 of this text.

26

An Introduction to Computers and QBasic

Robert Barnaby: a dedicated programmer; best known for writing WordStar, one of the most popular word processors. Word processing programs account for thirty percent of all software sold in the United States. The QBasic editor uses WordStar-like commands.

1980s William L. Sydnes: manager of the IBM Entry Systems Boca engineering group; headed the design team for the IBM Personal Computer. Shortly after its introduction in 1981, the IBM PC dominated the microcomputer field. QBasic runs on all IBM Personal Computers and compatibles.

Mitchell D. Kapor: co-founder of Lotus Corporation; wrote the business software program 1-2-3, the most successful piece of software for personal computers. Lotus 1-2-3 is an integrated program consisting of a spreadsheet, a database manager, and a graphics package. Databases are studied in Chapters 8 and 9 of this text and graphics in Chapter 10. Tom Button: group product manager for applications programmability at Microsoft; headed the team that developed QuickBasic, QBasic, and Visual Basic.

These modern, yet easy to use languages, have greatly increased the productivity of programmers. Alan Cooper: director of applications software for Coactive Computing Corporation; is considered the father of Visual Basic. In 1987 he wrote a program called “Ruby” that delivered visual programming to the average user. A few years later, Ruby was combined with QuickBasic to produce Visual Basic, the remarkably successful language that allows Windows programs to be written from within Windows easily and efficiently.

Problem Solving

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28

o

Problem Solving

i PROGRAM DEVELOPMENT

CYCLE

We learned in the first chapter that hardware refers to the machinery in a computer system (such as the monitor, keyboard, and CPU) and software refers to a collection of instructions, called a program, that directs the hardware. Programs are written to solve problems or perform tasks on a computer. Programmers translate the solutions or tasks into a language the computer can understand. As we write programs, we must keep in mind that the computer will only do what we instruct it to do. Because of this, we must be very careful and thorough with our instructions.

Designing

a Computer Program

The first step in designing a program is to determine what the output of the program should be, that is, exactly what the program should produce. The second step is to identify the data, or input, necessary to obtain the output. The last step is to determine how to process the input to obtain the desired output, that is, to determine what formulas or ways of doing things can be used to obtain the

output. This problem-solving approach is the same as that used to solve word problems in an algebra class. For example, consider the following algebra problem:

How fast is a car traveling if it goes 50 miles in 2 hours?

The first step is to determine the type of answer requested. The answer should be a number giving the rate of speed in miles per hour (the output). The information needed to obtain the answer is the distance and time the car has traveled (the input). The formula rate = distance / time

is used to process the distance traveled and the time elapsed in order to determine the rate of speed. That is, rate

50 miles/2 hours 25 miles/hour

A pictorial representation of this problem solving process is

Processing

We determine what we want as output, get the needed input, and process the input to produce the desired output. In the following chapters, we discuss how to write programs to carry out the above operations. But first, we look at the general process of writing programs.

2.1

PROGRAM

DEVELOPMENT CYCLE

29

Program Planning A recipe provides a good example of a plan. The ingredients and the amounts are determined by what is to be baked. That is, the output determines the input and the processing. The recipe, or plan, reduces the number of mistakes you might

make if you tried to bake with no plan at all. While it’s difficult to imagine an architect building a bridge or a factory without a detailed plan, many programmers (particularly students in their first programming course) frequently try to write programs without first making a careful plan. The more complicated the problem, the more complex the plan must be. You will spend much less time working on a program if you devise a carefully thought out step-by-step plan and test it before actually writing the program. Many programmers plan their programs using a sequence of steps, referred to as the program development cycle. The following step-by-step process will enable you to use your time efficiently and help you design error-free programs that produce the desired output.

1. Analysis: Define the problem. Be sure you understand what the program should do, that is, what the output should be. Have a clear idea of what data (or input) are given and the relationship between the input and the desired output.

2. Design: Plan the solution to the problem. Find a logical sequence of precise steps that solve the problem. Such a sequence of steps is called an algorithm. Every detail, including obvious steps, should appear in the algorithm. In the next section, we discuss three popular methods used to develop the logic plan: flowcharts, pseudocode, and top-down charts. These tools help the programmer break a problem into a sequence of small tasks the computer can perform to solve the problem. Planning also involves using representative data to test the logic of the algorithm by hand to ensure that it is correct. 3. Coding: Translate the algorithm into a programming language. Coding is the technical word for writing the program. During this stage, the program is written in QBasic and entered into the computer. The programmer uses the algorithm devised in step 2 along with a knowledge of QBasic. 4. Testing and debugging: Locate and remove any errors in the program.

Testing is the process of finding errors in a program and debugging is the process of correcting errors found during the testing process. (An error in a program is called a bug.) As the program is typed into the View window, QBasic’s smart editor points out certain types of program errors. Other types of errors will be detected by QBasic when the program is executed; however, many errors due to typing mistakes, flaws in the algorithm, or incorrect usages of the QBasic language rules can only be uncovered and corrected by

careful detective work. An example of such an error would be using addition when multiplication was the proper operation.

30

Problem Solving

5. Completing the documentation: Organize all the material that describes the program. Documentation is intended to allow another person, or the programmer at a later date, to understand the program. Internal documentation consists of statements in the program that are not executed, but point out the purposes of various parts of the program. Documentation might also consist of a detailed description of what the program does and how to use the program (for instance, what type of input is expected). For commercial programs, documentation includes an instruction manual. Other types of documentation are the flowchart, pseudocode, and top-down chart that were used to construct the program. Although documentation is listed as the last step in the program development cycle, it should take place as the program is being coded.

p

y. PROGRAMMING

TOOLS

This section discusses some specific algorithms and develops three tools used to convert algorithms into computer programs: flowcharts, pseudocode, and top-down charts. You use algorithms every day to make decisions and perform tasks. For instance, whenever you mail a letter, you must decide how much postage to put on the envelope. One rule of thumb is to use one stamp for every five sheets of paper or fraction thereof. Suppose a friend asks you to determine the number of stamps to place on an envelope. The following algorithm will accomplish the task. 1. Request the number of sheets of paper, call it Sheets.

(input)

2. Divide Sheets by 5.

(processing)

3. Round the quotient up to the next highest whole number,

(processing)

call it Stamps.

4. Reply with the number Stamps.

(output)

The algorithm above takes the number of sheets (Sheets) as input, processes the data, and produces the number of stamps needed (Stamps) as output. We can test the algorithm for a letter with 16 sheets of paper. 1. Request the number of sheets of paper, Sheets = 16. 2. Dividing 5 into 16 gives 3.2. 3. Rounding 3.2 up to 4 gives Stamps = 4. 4. Reply with the answer, 4 stamps.

2.2

PROGRAMMING

TOOLS

31

This problem-solving example can be pictured by

Processing (formulas)

Of the program design tools available, the three most popular are the following:

Flowcharts: Graphically depict the logical steps of the program and show how the steps relate to each other.

Pseudocode: program.

Uses English-like phrases with some QBasic terms to outline the

Top-down charts:

Show how the different parts of a program relate to each other.

Flowcharts

A flowchart consists of special geometric symbols connected by arrows. Within each symbol is a phrase presenting the activity at that step. The shape of the symbol indicates the type of operation that is to take place. For instance, the parallelogram denotes input or output. The arrows connecting the symbols, called flowlines, show the progression in which the steps take place. Flowcharts should “flow” from the top of the page to the bottom. Although the symbols used in flowcharts

are standardized,

no standards exist for the amount

of detail

required within each symbol. Below is a table of the flowchart symbols adopted by the American National Standards Institute (ANSI). Figure 2.1 contains the flowchart for the Postage

Stamp problem. Symbol

Name

Meaning

——

Flowline

Used to connect symbols and indicate the flow of logic.

Terminal

Used to represent the beginning (Start) or the end (End) of a program.

Input/Output

Used for input and output operations, such as reading and printing. The data to be read or printed are described inside.

Processing

Used for arithmetic and data-manipulation operations. The instructions are listed inside the symbol.

Decision

Used for any logic or comparison operations. Unlike the input/output and processing symbols, which have one entry

os

and one exit flowline, the decision symbol

has one entry and two exit paths. The path chosen depends on whether the answer to a question is “yes” or “no.”

32

Problem Solving

Connector

Used to join different flowlines.

Offpage Connector

Used to indicate that the flowchart continues to a second page.

Predefined Process

Used to represent a group of statements that perform one processing task.

Annotation

Used to provide additional information about another flowchart symbol.

Read

Set Stamps/5 S Bhaets

Round Stamps up to next whole number

Figure 2.1

|

ae

yor

+

processing

|

processing

|

output

Flowchart for the Postage Stamp Problem

The main advantage of using a flowchart to plan a program is that it provides a pictorial representation of the program, which makes the program logic easier to follow. We can clearly see every step of the program and how each step is connected to the next. The major disadvantage with flowcharts is that when a program is very large, the flowcharts may continue for many pages, making them hard to follow and modify.

2.2

PROGRAMMING TOOLS

33

Pseudocode Pseudocode is an abbreviated version of actual computer code (hence, pseudo-

code). The geometric symbols used in flowcharts are replaced by English-like statements that outline the program. As a result, pseudocode looks more like a program than does a flowchart. Pseudocode allows the programmer to focus on the steps required to solve a problem rather than on how to use the computer language. The programmer can describe the algorithm in QBasic-like form without being restricted by the rules of QBasic. When the pseudocode is completed, it can be easily translated into the QBasic language. The following is pseudocode for the Postage Stamp problem: Program: Determine the proper number of stamps for a letter Read Sheets Set the number of stamps to sheets/5 Round the number of stamps up to the next whole number Display the number of stamps

(input) (processing) (processing) (output)

Pseudocode has several advantages. It is compact and probably will not extend for many pages as flowcharts commonly do. Also, the plan looks like the code to be written and so is preferred by many programmers.

Top-Down Chart The last programming tool we'll discuss is the top-down chart, which shows the overall program structure. Top-down charts are also called hierarchy charts, HIPO (Hierarchy plus Input-Process-Output) charts, structure charts, or WTOC (Visual Table of Contents) charts. All these names refer to planning diagrams that are similar to a company’s organization chart. Top-down charts depict the organization of a program but omit the specific processing logic. They describe what each part, or module, of the program does and they show how the modules relate to each other. The details on how the modules work, however, are omitted.

The chart is read from top to bottom and from left to right. Each module may be subdivided into a succession of submodules that branch out under it. Typically, after the activities in the succession of submodules are carried out, the module

to the right of the original module is considered. A quick glance at the top-down chart reveals each task performed in the program and where it is performed. Figure 2.2 contains a top-down chart for the Postage Stamp problem.

Postage Stamp Program

Read Sheets

Calculate Stamps

| Set Stamps = Sheets/5

Bei la

Display Stamps

an Round Stamps up to next whole number

Figure 2.2. Top-Down Chart for the Postage Stamp Problem

34

Problem Solving

The main benefit of top-down charts is in the initial planning of a program. We break down the major parts of a program so we can see what must be done in general. From this point, we can then refine each module into more detailed plans using flowcharts or pseudocode. This process is called the divide and conquer method. The Postage Stamp problem was solved by a series of instructions to read data, perform calculations, and display results. Each step was in a sequence; that

is, we moved from one line to the next without skipping over any lines. This kind

of structure

is called a sequence

structure.

Many

problems,

however,

require a decision to determine whether a series of instructions should be executed. If the answer to a question is “Yes,” then one group of instructions is executed. If the answer is “No,” then another is executed. This structure is called a decision structure. Figure 2.3 contains the pseudocode and flowchart for a decision structure.

IF condition is true THEN P 1 rocess step(s) ELSE

No

Is

ee Condition fee

Yes

Process step(s) 2 END IF Process step(s) 2

Figure 2.3

Process

step(s) 1

Pseudocode and Flowchart for a Decision Structure

The sequence and decision structures are both used to solve the following problem.

Direction of Numbered New York Streets Algorithm Problem:

Given a street number of a one-way street in New York City, decide

the direction of the street, either eastbound or westbound.

Discussion: There is a simple rule to tell the direction of a one-way street in New York City: Even numbered streets run eastbound. Input: Street number

Processing: Decide if street number is divisible by 2. Output: “Eastbound” or “Westbound”

fe

Figures 2.4 through 2.6 contain the flowchart, pseudocode, and top-down “hart for the New York City Numbered Streets problem.

2.2

Figure 2.4

PROGRAMMING TOOLS

Display

Display

Westbound

Eastbound

Flowchart for the New York City Numbered Streets Problem.

Program: Determine the direction of a numbered NYC street Get Street IF Street is even THEN Display Eastbound ELSE Display Westbound END IF Figure 2.5

Pseudocode for the New York City Numbered Streets Problem

Street Direction

Program

Get

Decide if

Display

Street Number

Eastbound or Westbound

Direction

Figure 2.6 Top-Down Chart for the New York City Numbered Streets Problem

35

36

Problem Solving

The solution to the next problem requires the repetition of a series of instructions.

A programming structure that executes instructions many times is

called a loop structure. We need a test (or decision) to tell when the loop should end. Without an exit condition, the loop would repeat endlessly (an infinite loop). One way to control the number of times a loop repeats (often referred to as the number of passes or iterations) is to check a condition before each pass through the loop and continue executing the loop so long as the condition is true.

Is condition true?

DO WHILE condition is true Process step(s)

No

LOOP Process

step(s)

Figure 2.7

Pseudocode and Flowchart for a Loop

Class Average Algorithm Problem:

Calculate and report the grade-point average for a class.

Discussion: The average grade equals the sum of all grades divided by the number of students. We need a loop to read and then add (accumulate) the grades for each student in the class. Inside the loop we also need to total (count) the

number of students in the class. See Figures 2.8 through 2.10. Input: Student grades

Processing: Find the sum of the grades; count the number of students; calculate average grade = sum of grades / number of students. Output: Average grade

2.2

Initialize Counter and Sum to 0

PROGRAMMING TOOLS

Counter and

Sum start at 0

--

|

pei

read

Are there more

data?

Increment

Counter

Add Grade to Sum

Set Average to SunVCounter

Display Average

Program: Determine the average grade of a class Initialize Counter and Sum to 0 Get the first Grade DO WHILE there are more data Add the Grade to the Sum Increment the Counter Get the next Grade LOOP

Compute Average = Sum / Counter Display Average

Figure 2.8 Flowchart for the Class Average Problem

Figure 2.9 Pseudocode for the Class Average Problem

37

38

Problem Solving

Class Average Program

Get Grade

Figure 2.10

Calculate Average

Compute Sum

Display Average

Top-Down Chart for the Class Average Problem

Comments:

is Tracing a flowchart is like playing a board game. We begin at the Start symbol and proceed from symbol to symbol until we reach the End symbol. At any time we will be at just one symbol. In a board game, the path taken depends on the result of spinning a spinner or rolling a pair of dice. The path taken through a flowchart depends on the input.

The algorithm should be tested into a program. Different data checked. This process is known include nonstandard data as well

at the flowchart stage before being coded should be used as input and the output as desk-checking. The test data should as typical data.

Flowcharts, pseudocode, and top-down charts are universal problem-solving tools. They can be used to construct programs in any computer language, not just QBasic. Flowcharts are used throughout this text to provide a visualization of the flow of certain programming tasks and QBasic control structures. Major examples of pseudocode and top-down charts appear in the case studies. There are four primary logical programming constructs: sequence, decision,

loop, and unconditional branch. Unconditional branch, which appears in some languages as GOTO statements, involves jumping from one place in a program to another. Structured programming uses the first three constructs, but forbids the fourth. One advantage of pseudocode over flowcharts is that pseudocode has no provision for unconditional branching and thus forces the programmer to write structured programs.

Flowcharts are time consuming to write and update. For this reason, professional programmers are more likely to favor pseudocode and top-down charts. Since flowcharts so clearly illustrate the logical flow of programming techniques, however, they are a valuable tool in the education of programmers.

There are many styles of pseudocode. form, whereas others use a form that language. The pseudocode appearing in on the primary tasks to be performed by routine details to be completed during

Some programmers use an outline looks almost like a programming the case studies of this text focuses the program and leaves many of the the coding process. Several QBasic

keywords, such as READ, PRINT, IK DO, and WHILE, are used extensively

in the pseudocode appearing in this text.

Many people draw rectangles around each item in a top-down chart. In this text, rectangles are omitted to encourage the use of top-down charts by making them easier to draw.

Fundamentals of QBasic

40

3

Fundamentals of QBasic

1 NUMBERS Much of the data processed by computers consist of numbers. In “computerese,” numbers are often called numeric

constants. This section discusses the

operations that are performed with numbers and the ways numbers are displayed.

Arithmetic Operations The five arithmetic operations are addition, subtraction, multiplication, division, and exponentiation. (Since exponentiation is not as familiar as the others, it is reviewed in detail in Comment 12.) Addition, subtraction, and division are denoted in QBasic by the standard symbols +, —, and /. However, the notations

for multiplication and exponentiation differ from the customary mathematical notations. Mathematical Notation

a-b

or axb a’

QBasic Notation

a*b ar

(The asterisk [*] is the upper character of the 8 key on the top row of the keyboard. The caret [“] is the upper character of the 6 key at the top of the keyboard.) Note: In this book, the proportional font used for text differs from the monospaced font used for programs. In the program font, the asterisk appears as *. If n is any number, then the statement PRINT

n

displays the number n on the screen. If the PRINT statement is followed by a combination of numbers and arithmetic operations, it carries out the operations and displays the result.

EXAMPLE

1

The following program applies each of the five arithmetic operations to the numbers 3 and 2. Notice that 3 / 2 is displayed in decimal form. QBasic never displays numbers as common fractions. Note 1: The star in the fourth and seventh lines is the computer font version of the asterisk. Note 2: The notation [run] indicates that Shift+F5 is pressed to execute the program. CIES PRIN

SiectaerZ

PRINT

3

- 2

PRINTS

ee

PRINT 3 / 2 PRINTS

3a

PRINT

2

END

[run] 5 1

6 Wes 9

a2 *

(3

+

4)

3.1

NUMBERS

41

Scientific Notation

Let us review powers of 10 and scientific notation. Our method of decimal notation is based on a systematic use of exponents.

10! = 10 10° = 100 10? = 1000

107! = 1/10 =.1 10 = .01 107 = .001

10"=1000...0

10° = .000...01

n zeros

n digits

Scientific notation provides a convenient way of writing numbers by using powers of 10 to stand for zeros. Numbers are written in the form b-10", where b isanumber from | up to (but not including) 10, andr is an integer. For example, it is much more convenient to write the diameter of the sun (1,400,000,000 meters) in scientific notation: 1.4-10? meters. Similarly, rather than write

.0000003 meters for the diameter of a bacterium, it is simpler to write 3-107 meters. Any acceptable number can be entered into the computer in either standard or scientific notation. The form in which QBasic displays a number depends on many factors, with size being an important consideration. In QBasic, b-10" is usually written as bEr. (The letter E is an abbreviation for exponent.) The following forms of the numbers mentioned above are equivalent. 143 1049. J

AOD—7

1 4E +09 SI 4 Eos oo SE-OF

3E-7

1 4Ro

1400000000

0000003

The computer displays r as a two-digit number, preceded by a plus sign if r is positive and a minus sign if 7 is negative.

EXAMPLE 2

The following program illustrates scientific notation. The computer’s decision of whether to display a number in scientific or standard form depends on the magnitude of the number. CLS PRENT PRUNES PROCN PRINT PRINT END

GL cenlOne 33.4 Zea LOROSS ileal Olas 10 “~ -20 10 * -2

[run] 1.2E+34 1.2E+08

1200 1E-20 lO

42

Fundamentals of QBasic

Numeric Variables

In applied mathematics problems, quantities are referred to by names. For instance, consider the following high school algebra problem. “If a car travels at 50 miles per hour, how far will it travel in 14 hours? Also, how many hours are required to travel 410 miles?” The solution to this problem uses the well-known formula distance = rate X time

Here’s how this problem would be solved with a computer program. GIES LET

rate

= 50

LET

time

=

LET

distance

PRINT LET

14 = rate

* time

distance distance

LET time PRINT

= 410

= distance

/ rate

time

END

[run] 700 2

The second line sets the rate to 50 and the third line sets the time to fourth line multiplies the value for rate by the value for time and sets to this product. The next line displays the answer to the first question. three lines before the END statement answer the second question in manner.

14. The distance The last a similar

The names rate, time, and distance, which hold numbers, are referred to as

variables. Consider the variable time. In the third line its value was set to 14. In the seventh line its value was changed as the result of a computation. On the other hand, the variable rate had the same value, 50, throughout the program. In general, a variable is a name that is used to refer to an item of data. The value assigned to the variable may change during the execution of the program. In QBasic, variable names can be up to forty characters long, must begin with a letter, and can consist only of letters, digits, and periods. (The shortest variable names consist of a single letter.) QBasic does not distinguish between upper and lowercase letters used in variable names. Some examples of variable names are total, numberOfCars,

taxRate.1994,

and n. As a convention,

we will keep

variable names in lowercase letters except for the first letters of additional words (as in numberOfCars). LET statements are used to assign values to variables and PRINT statements are used to display the values of variables. If var is a numeric variable and num is a numeric constant, then the statement LET

var

= num

3.1

NUMBERS

43

assigns the number num to the variable var. Actually, the computer sets aside a location in memory with the name var, and places the number num in it. The statement PRINT

var

looks into this memory location for the value of the variable and displays the value on the screen. A combination of constants, variables, and arithmetic operations that can be evaluated to yield a number is called a numeric expression. Expressions are evaluated by replacing each variable by its value and carrying out the arithmetic. Some examples of expressions are 2 * time + 7,n + 1, and (a + b) / 3.

(2 + b)

+

CLS LET LET b PRINT a END

Pm

The following program displays the value of an expression.

u

EXAMPLE 3

[run] 30

If var is a variable, then the statement LET

var

= expression

first evaluates the expression on the right and then assigns its value to the variable. For instance, the program in Example 3 can be written as CLS LETial=—5 LET

LET

b

= 4

c =a

*

(2 + b)

PRINTc END

The expression a * (2 + b) is evaluated to 30 and then this value is assigned to the variable c.

Since the expression in a LET statement is evaluated before an assignment is made, a statement such as DEM

te=

tet al

is meaningful. It first evaluates the expression on the right (that is, it adds 1 to the original value of the variable t), and then assigns this sum to the variable t.

The effect is to increase the value of the variable t by 1. In terms of memory locations, the statement retrieves the value of t from t’s memory location, uses

it to compute t + 1, and then places the sum in t’s memory location.

44

Fundamentals of QBasic

PRINT

Statement

Consider the following program. CLS PRINT PRINT END

3 -3

[run] 3 -3

Notice that the negative number —3 begins directly at the left margin, whereas the positive number 3 begins one space to the right. The PRINT statement always displays nonnegative numbers with a leading space. The PRINT statement also displays a trailing space after every number. Although the trailing spaces are not apparent here, we will soon see evidence of their presence.

leading space

i

trailing space

The PRINT statements considered so far only display one number per line. After displaying a number, the cursor moves to the leftmost position and down a line for the next display. Borrowing some typewriter terminology, we say that the computer performs a carriage return and a line feed after each number is displayed. The carriage return and line feed, however, can be suppressed by placing a semicolon at the end of the PRINT statement.

EXAMPLE 4

The following program illustrates the use of semicolons in PRINT statements. The output reveals the presence of the space trailing each number. For instance, the space trailing —3 combines with the leading space of 99 to produce two spaces between the numbers. CLS PRINT

3;

PRINT

-33

PRINT

99;

PRINT

100

END

[run] 31-3)

995100

Semicolons can be used to display several numbers with one PRINT statement. If m, n, and r are numbers, a statement of the form PRINT

ms:

ins)

35

PRINT

m3

n3

r

or

3.1

NUMBERS

45

displays the three numbers, one after another, separated only by their leading and trailing spaces. For instance, the PRINT statements in Example 4 above can

be replaced by the single line PRINT

3;

-3;

99;

100

Comments:

1. Numbers must not contain commas, dollar signs, or percent signs. Also, mixed numbers, such as 84, are not allowed.

Ze In this text we use lowercase letters for variable names. For names such as interestRate, however, we capitalize the first letter of the second word to

improve readability. QBasic allows any type of capitalization you like and helps you to be consistent with the use of uppercase letters in a variable name. For instance, if you use the variable name interestRate in a program and later enter a line using InterestRate, the appearance of the first variable name will automatically be changed to InterestRate by QBasic.

Some people think of the equals sign (=) in a LET statement as an arrow pointing to the left. This stresses the fact that the value on the right is assigned to the variable on the left. Parentheses should be used when necessary to clarify the meaning of an expression. When there are no parentheses, the arithmetic operations are performed in the following order: (1) exponentiations; (2) multiplications and divisions; (3) additions and subtractions. leftmost operation is carried out first.

In the event of ties, the

Level of Precedence for Arithmetic Operations ( ) A

Inner to outer, left to right Left to right in expression

* / + —

Left to right in expression Left to right in expression

QBasic statements and certain other words that have a specific meaning in the QBasic language cannot be used as names of variables. For instance, the statements LET print = 99 and LET end = 99 are not valid. These words are called keywords (or reserved words). Some keywords that are most likely to be used inadvertently are COLOR, ERROR, INT, KEY, POS, SELECT, VAL, and WIDTH. To view the list of keywords, press Alt/H/I and then use

the PgDn and PgUp keys to scroll through the list. Every capitalized word in the listing is a keyword. Grammatical errors, such as misspellings or incorrect punctuations, are called syntax errors. Certain types of syntax errors are spotted by the smart editor when they are entered, whereas others are not detected until the program is executed. When QBasic spots an error, it displays a dialog box. Some incorrect statements and their errors are given below. Statement

Reason for Error

PRIMT 3 PRINT 24 LET 9W =5

Misspelling of keyword No number follows the plus sign 9W is not a valid variable name

46

Fundamentals of QBasic

7. Numeric variables that have not been assigned values by LET statements have the value 0. We say that the default value is 0. GIES Hel @ = & PRINT a9 b3))b END

[run] 0)

8. When a variable is first assigned a value, we say that the variable is initialized. The failure to initialize variables can cause some programs to malfunction. Uninitialized numeric variables have the value 0. 9. The statement LPRINT produces an output on the printer identical to the display on the screen produced by PRINT.

10. The omission of the asterisk to denote multiplication is a common error. For instance, the expression a(b + c) is not valid. It should read a * (b + c).

11. The largest represent is the message usually have

number the numeric variables considered in this text can 3.402823E+38. Attempting to generate larger values produces “Overflow.” The numbers generated by the programs in this text a maximum of seven digits.

12. A Review of Exponents. The expression 2? means 2 - 2 - 2, the product of three 2’s. The number 3 is called the exponent, and the number 2 is called the base. In general, ifr is a positive integer and a is a number, then a’ is defined as follows:

r factors

The process of calculating a’ is called raising a to the rth power. Some other types of exponents are:

Ae

ee

gli2 _

ain = Vq

N positive integer

16!/4 = 2

qmin . (Va)™

m, N positive integers

82/3 = (V8) =4

a* = fat

a#0

10% = 01

13. More than one statement can be placed on a single line of a program provided the statements are separated by colons. For instance, the program in Example 3 can be written as CLS END

eLET =a 2 5:

LE]

bowed

PRINT

al*

(2.45)

In general, though, programs are much easier to follow if just one statement appears on each line. In this text we almost always use single-statement lines.

3.1

NUMBERS

47

PRACTICE PROBLEMS 3.1 1. Evaluate 2 + 3 * 4.

2. Complete the table by filling in the value of each variable after each line of the program is executed.

Pos,

CEMal=—3

4

PRINT a - b WEI |e) Solo)

Ip

EXERCISES 3.1 In Exercises 1 through 10, evaluate the numeric expression.

Loa

2eL ter

3. LPNS

4.34+4%*5

5. (5-3) *4

6.3

(OI

Oe

Dalek 1)

(-2)5

3 =

B.A D3 84

#22 )5

LOS O165 Oe)

In Exercises 11 through 14, write the number in scientific notation as it might

be displayed by the computer. 11. 3 billion

12.123300,000

13.4/10%8

14,32

10420

In Exercises 15 through 20, determine whether or not the name is a valid variable name.

15. temperature

16. Roads&pavements

17. force.1ONewtons

18. 100Volts

19. Viscosity?

20. INTEL80386

48

Fundamentals of QBasic

In Exercises 21 through 28, evaluate the numeric

expression where a = 2,

b =3,and=c4. (bee)

Zeng

ae

22a

Daler

Oe

24.a%c a) b 26-(c=

25nd Osea) aloe

2c

b

a form “bp a 28

In Exercises 29 through 38, write a QBasic program to calculate the value of the expression.

29785

201 (le 2-9)

31. 5.5% of 20

Bae

3317.6 + 102)

34. 44=3°4

35.1

yo ome

io

ue

1

eerie 63, 37. ee

33)

3

a

314 va 11 3 19% pe

1.6

1

In Exercises 39 and 40, complete the table by filling in the value of each variable after each line of the program is executed. 39.

ey Gere eee [ec el |) Oa Reiachs rai al, ss es

3.1

NUMBERS

In Exercises 41 through 50, determine the output of the program. 41. LET amount PRINT

= 10

amount

42. LET a = 4

- 4

PETS

END

Da=95)

PRINT END

LET

4

3;

a+b;

b-a

44. LET number = 5

43. PRINT 1; 2; PRINT

2a

PRINT 5 + 6 END

number

= 2 * number

PRINT number END

45. LET x = 3 PRINT x ~ x3; x +3 END

46. LET n = 2 PRIN3 T* n LETn =n+n

* x

n +n

PRINT

END

47. LET massl1 = 4 acceleration

LET

= 5

* acceleration

massl

LET forcel = LET mass2 = LET force2 = PRINT forcel

10 * acceleration

mass2

+ force2;

force2

- forcel

END

48. LET electronCharge LET

voltage

LET

electronVolt

PRINT END

=

= 1.6E-19

1 = electronCharge

* voltage

electronVolt

49. LET current = 200 LET

current

PRINT

= 25

+ current

current

END

50. LET density LET

volume

LET

mass

= 1 = 4

= density

PRINT mass LET volume = 5 LET mass = mass PRINT mass END

* volume

+ density

* volume

In Exercises 51 through 54, identify the errors. S51. UE

az

(2

52. LET

YE ys WE @) ae 1) Se PRINT c

LET balance = 800 PRINT interest * balance END

END

53. LET balance LET deposit PRINT

END

balance

.05 = interest

= 1,234 = $100 + deposit

49

50

Fundamentals of QBasic

54. LET neutronNumber

= 1

LET electronNumber = protonNumber = 1 PRINT neutronNumber + protonNumber END

In Exercises 55 and 56, rewrite the program with fewer statements. 55. PRINT 1; PRINT PRINT END

2; 1 + 2

56. LET speed = 55 time = 2 distance = speed PRINT distance END LET LET

* time

In Exercises 57 through 64, write a program beginning with a CLS statement, ending with an END statement, and having one line for each step. 57. The following steps calculate a company’s profit. (a) Assign the value 98456 to the variable revenue. (b) Assign the value 45000 to the variable costs.

(c) Assign to the variable profit, the difference between the variables revenue and costs. (d) Display the value of the variable profit. 58. The following steps calculate the amount of work done by a force moving a body a certain distance in the direction of the force. (a) Assign the value 160 to the variable force. (b) Assign the value 14 to the variable distance. (c) Assign the product of force and distance to the variable work. (d) Display the value of the variable work.

59. The following steps calculate the price of an item after a 30% reduction.

(a) Assign the value 19.95 to the variable price. (b) Assign the value 30 to the variable discountPercent.

(c) Assign the value of discountPercent divided by 100 times price to the variable markDown. (d) Decrease price by markDown. (e) Display the value of price.

60. The following steps calculate the kinetic energy of a body in motion. (a) Assign the value 2000 to the variable mass. (b) Assign the value 20 to the variable velocity.

(c) Assign the value 1/2 times the value of mass times the square of the value of velocity to the variable kineticEnergy. (d) Display the value of the variable kineticEnergy.

61. The following steps calculate the balance after three years when $100 is deposited at the beginning of each year in a savings account at 5% interest compounded annually. (a) Assign the value 100 to the variable balance. (b) Increase the variable balance by 5% of its value and add 100.

3.1

NUMBERS

51

(c) Increase the variable balance by 5% of its value and add 100. (d) Increase the variable balance by 5% of its value and add 100. (e) Display the value of the variable balance.

62. Beginning with 10 grams of radioactive cobalt, the following steps calculate the amount remaining after three years. (a) (b) (c) (d)

Assign the value 10 to the variable radioCobalkt. Decrease the variable radioCobalt by 12% of its value. Decrease the variable radioCobalt by 12% of its value. Decrease the variable radioCobalt by 12% of its value.

(e) Display the value of the variable radioCobalkt. 63. The following steps calculate the balance after ten years when $100 is deposited in a savings account at 5% interest compounded annually. (a) Assign the value 100 to the variable balance. (b) Multiply the variable balance by 1.05 raised to the 10th power. (c) Display the value of the variable balance.

64. The following steps calculate the percentage reduction in area of a material resulting from a compressive force. This value is a measure of the ductility of the material, the ability of being easily molded or shaped.

(a) Assign the value .6 to the variable originalArea. (b) Assign the value .501 to the variable finalArea. (c) Assign to the variable ductility, one hundred times the value of the

difference between originalArea and finalArea divided by originalArea. (d) Display the value of the variable ductility. In Exercises 65 through 74, write a program to solve the problem. The program should use variables for each of the quantities. 65. Suppose each acre of farmland produces 18 tons of corn. How many tons of corn can be produced on a 30-acre farm?

66. Suppose a ball is thrown straight up in the air with an initial velocity of 50 feet per second and an initial height of 5 feet. How high will the ball be after 3 seconds? (Note: The height after t seconds is given by the expression —16t? + uot + ho, where vp is the initial velocity and hg is the initial height.) . Ifa car left Washington, D.C. at two o’clock and arrived in New York at seven o'clock, what was its average speed? (Note: New York is 233 miles from Washington.) . A motorist wants to determine her gas mileage. At 23,340 miles (on the odometer), the tank is filled. At 23,695 miles, the tank is filled with 14.1

gallons. How many miles per gallon did the car average between the two fillings?

.A US. geological survey showed that Americans use an average of 1600 gallons of water per person per day, including industrial use. How many gallons of water are used each year in the United States? (Note: The current population of the U.S. is about 260 million people.)

52

Fundamentals of QBasic

70. One mole of a chemical element or compound is the quantity whose weight in grams is numerically equivalent to its atomic or molecular weight in atomic mass units. For example, a mole of oxygen (atomic weight 16) is 16 grams, a mole of carbon (atomic weight 12) is 12 grams, and a mole of carbon

dioxide

(CO,

of carbon

one atom

two of oxygen)

and

is 44 grams

(12 + 16 + 16). Table 3.1 gives selected atomic weights. What

are the

weights in grams of a mole of each of the following elements and compounds? (a) He (helium) (b) O2 (molecular oxygen) (c) H2O (water)

(d) H,SO, (sulfuric acid) (e) NaCl (salt) (f) NaOH (caustic soda)

Element

Atomic weight

Element

Atomic weight

H

1

Na

23

He

4

S

52

O

16

Cl

B5

Table 3.1

Elements and their Atomic Weights

71. According to FHA specifications, each room in a house should have a window area equal to at least 10 percent of the floor area of the room. What is the minimum window area for a 14-foot by 16-foot room? 72. If a light-year is 5,878,000,000,000 miles and the distance of the star Sirius

from Earth is 9 light-years, how many miles is Sirius from Earth? 73. Ifa barrel holds 5.8 cubic feet and the dimensions of a rectangular container of oil are 2 ft. x 3 ft x 4 ft., how many barrels of oil does the container hold?

74. If a baseball is pitched at 90 feet per second and home plate is 60.5 feet from the pitcher’s mound, how long will it take for the ball to reach the batter? SOLUTIONS TO PRACTICE PROBLEMS 3.1 1. 14. Multiplications are performed before additions. If the intent is for the addition to be performed first, the expression should be written (2 + 3) * 4.

PRINT

a - b

Each time a LET statement is executed, only one variable has its value changed (the variable

to the left of the equals sign).

DLO

LRINGS

753

3 : WD STRINGS There are two types of data that can be processed by QBasic: numbers and strings. Sentences, phrases, words, letters of the alphabet, names, phone numbers, addresses, and dates are all examples of strings. Formally, a string constant

is a sequence of characters that is treated as a single item. Strings can be assigned names with LET statements, can be displayed with PRINT statements, and there is an operation called concatenation (denoted by +) for combining strings.

String Variables A string variable is a name used to refer to a string. The allowable names of string variables are identical to those of numeric variables with one modification: each string variable name must be followed by a dollar sign ($). The value of a string variable is assigned or altered with LET statements and displayed with PRINT statements just like the value of a numeric variable.

EXAMPLE

1

The following program shows how LET and PRINT statements are used with strings. The string variable today$ is assigned a value by the third line and this value is displayed by the fourth line. The quotation marks surrounding each string constant are not part of the constant and are not displayed by the PRINT statements. CLS PRINT

"hello"

LET today$ = "9/17/94" PRINT

today$

END

[run] hello

9/17/94 If

x,y,

...,

BEDeVorg.=

yare characters and var$ is a string variable, then the statement "XY oraz

assigns the string constant xy...z to the variable, and the statement DRUND Mex

area Zi

or

PRINT

var$

displays the string xy...z on the screen. If var2$ is another string variable, then the statement LET

var2$

= var$

assigns the value of the variable var$ to the variable var2$. (The value of var$ will remain the same.) String constants used in LET or PRINT statements must

54

Fundamentals of QBasic

by d nde rou sur r neve are s able vari ng stri but s, mark ion tat quo by d nde rou sur be quotation marks. As with numbers, semicolons can be used with strings in PRINT statements to suppress carriage returns and line feeds. However, PRINT statements do not display leading or trailing spaces along with strings.

EXAMPLE 2

The following program illustrates the use of the LET and PRINT statements. GES

LET phrase$ PRINT "It's PRINT "It's

= "win or lose that counts." not whether you "; phrase$ whether I "; phrase$

END

[run] It's

not

whether

It's

whether

you

I win

or

win

or

lose

lose that

that

counts.

counts.

Concatenation

Two strings can be combined to form a new string consisting of the strings joined together. The joining operation is called concatenation and is represented by a plus sign (+). For instance, “good” + “bye” is “goodbye”. A combination of strings and plus signs that can be evaluated to form a string is called a string expression. The LET and PRINT statements evaluate expressions before assigning them to variables or displaying them.

EXAMPLE 3

The following program illustrates concatenation. GES

LET quotel$ LET quote2$ LET quote$ = PRINT quote$

= "The ballgame isn't = "until it's over." quotel$ + quote2$ + " Yogi Berra"

over,

"

END

[run] The ballgame

EXAMPLE 4

isn't

over,

until

it's

over.

Yogi

Berra

The following program has strings and numbers occurring together in a PRINT statement.

GES LET

interestRate

=

.0655

LET principal = 100 PRINT "The balance after END

[run] The balance

after

a year

a year

is

is";

106.55

(1 + interestRate)

* principal

STRINGS.

SO

155

ASCII Table Each of the 47 keys in the center typewriter portion of the keyboard can produce two characters, for a total of 94 characters. Adding | for the space character produced by the space bar makes 95 characters. Many more characters can be displayed. Appendix A shows the complete table of characters, numbered 0 to 255, that the computer recognizes. (The number assigned to each character is called its ASCII value.) The keyboard characters appear with numbers 32 to 126. Figures 3.1 to 3.4 show some different types of characters. The box-drawing characters in Figure 3.3 have been grouped to show how they fit together. The characters in these figures are referred to by their ASCII values. Ifn is a number between 0 and 255, then CHR$(n)

Poo

oe

4S

_

1:

=

~

=

ee oy fie ee ec,

=

ze

-§-

—»

[rod

ma cis oY met Met

fo

(RS Al) eas

2 oe

bad

pies

ae

lie a

tk +4

ag]

de

ft

#4

J

oS

Box-Drawing Characters (179 to 218)

PU Pt Figure 3.4

i~

i

oes

Cee pe (eR

Figure 3.3.

=

Foreign Language Characters (128 to 168)

od

Figure 3.1

=e

We ake We ett

=i

is the string consisting of the single character with ASCII value n. For instance, CHR$(227) is the string consisting of the Greek letter pi.

Bik Pia Sees, ocd intel *lentsRat fo) > eb 20000 THEN

END END

END IF

PRINT PRINT IF

in

a bar

by

a force.

"A stress of 20,000 to 26,000 " an elongation of 1.4 mm"

causes";

31.1F j = 7 THEN LETED ="1 ELSE IF j 7 THEN LET b= 2 END IF END IF

32. IF a < b THEN LE bec PRINT

END 33.

INPUT

IF

END IF "Is

THEN b;

"is

between";

a;

"and";

c

IF

Alaska

bigger

than

LEFT$(answer$, 1) = "Y" LET answer$ = "YES" END IF IF LEFT$(answer$, 1) = “y" LET answer$ = "YES" END IF IF answer$ = "YES" THEN PRINT "Correct" ELSE PRINT "Wrong" END IF END

Texas

THEN

THEN

and

California

combined";

answer$

IF BLOCKS:

4.2

34. INPUT "How tall

(in THEN

ft.)

is

IF feet 141 THEN IF feet < 161 THEN PRINT "Close" ELSE PRINT "Nope" END IF END IF PRINT "The Statue of Liberty END

the

Statue

of

Liberty";

feet

is

151.08

ft

from

to

base

129

torch."

Ser Write a program to determine how much to tip the bartender in a fine restaurant. The tip should be 15 percent of the check with a minimum of $1. 36. Write a quiz program to ask “What is the unit of power?” The program should display “Correct” if the answer is “Watt” or should display “No, a Watt.” otherwise. 3%. A computer store sells diskettes at $1 each for small orders or at 70 cents apiece for orders of 25 diskettes or more. Write a program that requests the number of diskettes ordered and displays the total cost. (Test the program for purchases of 5, 25, and 35 diskettes.)

38. A particle, originally at rest, is subjected to a force F whose direction is constant but whose magnitude varies with time according to the relation

Pare

Din)

for t between 0 and T (Fy and T are constants). For t > T, F = Fy and for t< 0, F = 0. Write a program that requests the value of Fo, T, and t as input and displays the value of F. Test the program with the responses Fo = 5 newtons, T = 100 seconds, and t = 89 seconds.

39. A copying center charges 5 cents per copy for the first 100 copies and 3 cents per copy for each additional copy. Write a program that requests the number of copies as input and displays the total cost. (Test the program with the quantities 25 and 125.)

40. Write a program that requests the names of three chemical elements and their proton and neutron numbers as input, and calculates their mass numbers. (Mass number = proton number + neutron number.) The program then should display the elements and their mass numbers in order from the highest to the lowest mass number. (Test the program with the responses Hydrogen, 1, 1; Sodium, 11, 12; and Oxygen, 8, 8.)

. Write a program to handle a savings account withdrawal. should request the current balance and the amount of the input and then display the new balance. If the withdrawal the original balance, the program should display “Withdrawal

The program withdrawal as is greater than denied.” If the

new balance is less than $150, the message “Balance below $150” should be

displayed.

130

Decisions

e rag ave the ys pla dis and ut inp as es scor e thre ts ues req that m gra pro a te Wri 42. of the two highest scores.

the ests requ that m gra pro a te Wri ts. digi e thre es duc pro g win dra ery lott A 43. three digits as input and then displays “Lucky seven” if two or more of the digits are 7.

44,

Federal law requires hourly employees be paid “time-and-a-half” for work in excess of 40 hours in a week. For example, if a person’s hourly wage is $8 and he works 60 hours in a week, his gross pay should be

(40-8) + (1.5 -8- (60 —40)) = $560. Write a program that requests as input the number of hours a person works in a given week and his hourly wage, and then displays his gross pay.

45. Write a program that requests a word (with lowercase letters) as input and translates the word into pig latin. The rules for translating a word into pig latin are: (a) If the word begins with a consonant, move the first letter to the end of

the word and add ay. For instance, chip becomes hipcay. (b) If the word begins with a vowel, add way to the end of the word. For instance, else becomes elseway. 46. The work done by a force F in changing the elongation of a spring, of stiffness K, from X, to X, is

W = K(X) =X) where X, and X; are the initial and final lengths of the spring respectively. The work done by a load P to elongate a bar by an amount delta is

W = EA - delta? / (2L) where E

is the elasticity,

A is the

area of a cross section,

delta

is the

elongation, and L is the length of the bar. Write a program that requests the body type (Spring or Bar) as input. If the body is a spring, the program should request the values of K, X,, and X,; if it is a bar, the program should request the values of E, A, delta, and L. Then the program should calculate the work

and display the result. (Try the program with the responses Spring, K = 8 Joules/meter’, X, = .1 meters, X, = .115 meters, and the responses Bar, E = 2 - 10!! Joules/meter’, L = 2.0 meters, A = 12 - 10 meters’, delta = 1.4 - 10° meters. )

47. The current calendar, called the Gregorian calendar, was introduced in 1582. Every year divisible by 4 was declared to be a leap year with the exception of the years ending in 00 (that is, those divisible by 100) and not divisible by 400. For instance, the years 1600 and 2000 are leap years, but 1700, 1800, and 1900 are not. Write a program that requests a year as input and states whether or not it is a leap year. (Test the program on the years 1994, 1996, 1900, and 2000.)

48. Write a program that requests the lengths of three line segments as input and tells whether the lines can form a triangle. Note: The lines can form a triangle if the length of the longest line is less than the sum of the lengths of the other two lines.

4.2

IFBLOCKS

131

49. Write a program that requests a number from 1 through 9999 as input and displays the number of digits in the number. A sample run is [run]

Enter The

a number

number

has

from

1 through

9999:

875

3 digits.

50. The flowchart in Figure 4.3 calculates New Jersey state income tax. Write a program corresponding to the flowchart. (Test the program with taxable incomes of $15,000, $30,000, and $60,000.)

Income
0 Oe

cmCRG sme taeecr

3 17 LET price = 5.00 END SELECT PRINT price

SELECT CASE n CASE 5 PRINT "case CASE 5 TO 7 PRINT "case CASE 7 TO 12 PRINT "case END SELECT END

END

Cleo ie2)

1" 2"

3"

(8.55017) 3. INPUT word$ SELECT CASE LEFT$ (word$, 1) CASE ALON eZ PRINT "Begins with an uppercase letter." CASE "a" TO "z" PRINT "Begins with a lowercase letter." CASE ELSE PRINT "Does not begin with a letter." END SELECT END

(apple, Zebra, 49ers) 4. REM List of environmental factors that affect REM limits of a gas or vapor. INPUT n SELECT CASE n CASE 1 PRINT "Temperature:" PRINT "Lower flammability limits decrease PRINT "temperature increases." CASE 2 PRINT "Pressure: " PRINT "Upper flammability limits increase PRINT "pressure increases." CASE 3 PRINT "Oxygen:" PRINT "Upper flammability limits increase PRINT “oxygen concentration increases." END SELECT END

(1, 2, 3)

flammability

as

";

as

";

as

";

140

Decisions

5. INPUT "In what year was the SELECT CASE year CASE 1945 PRINT "Correct" CASE 1943 TO 1947 PRINT "Close, 1945."

CASE IS PRINT CASE IS PRINT END SELECT END

< 1943 "Sorry, 1945. Work > 1947 "No, 1945. By then

ENIAC

on IBM

computer

the had

completed";

began

ENIAC built

in

a stored

June

year

1943."

program

computer."

(1940, 1945, 1950) 6. REM Type of nondegenerate conic INPUT "Enter coefficient of x * INPUT "Enter coefficient of x * INPUT "Enter coefficient of y * ac SEUEGIMCAS Ee Da 204 ete de CASE IS < 0 PRINT "circle or ellipse" CASE 0 PRINT "parabola" CASE ELSE PRINT "hyperbola" END SELECT END

section 2:", a y:", b 2:", c

(2, 0, -1) 7. REM State a quotation LET a = 3 LET a$ = "hello" INPUT b SEUEGTECASENZave De CASE

el

a * a

PRINT

"Less

is more."

CASE IS > LEN(a$) PRINT "Time keeps everything from happening at once." CASE ELSE PRINT "The less things change, the more they remain the END SELECT END

same."

(755.16) 8.

INPUT

"Who

developed

the

stored

program

concept";

name$

SELECT CASE UCASE$(name$) CASE "JOHN VON NEUMANN", "VON NEUMANN" PRINT "Correct" CASE "JOHN MAUCHLY", "MAUCHLY", "J. PRESPER ECKERT", "ECKERT" PRINT "He worked with the developer, von Neumann, on the ENIAC." CASE ELSE PRINT "Nope" END SELECT END

(Grace Hopper, Eckert, John von Neumann)

SELECT CASE BLOCKS

4.3

9.

INPUT

141

whatever

SELECT

CASE

CASE

EESE

PRINT

whatever

"Hi"

SELECT

END END C7

1)

10. The rotation of a body with a constant angular acceleration is described by theta(t) = alpha - t?/2+ wo -t + thetag

where theta(t) is the rotation angle at time t, thetag is the rotation angle at time t = 0, wg is the initial angular velocity, and alpha is the angular acceleration. REM

Determine

the

PRINT

"Enter

PRINT

" alpha,

the

time

given

values

of

wO,

theta,

the

the and

other

variables.

coefficients"; theta0"

INPUT alpha, wO, theta, theta0 SELECT CASE wO * 2 - 2 * alpha * (thetaO - theta) CASESIS#= 2 AND a < 3 THEN PRINT "The process is adiabatic." REM No heat is transferred in or out. END IF IF a = 3 OR (3 < a AND a = 6 THEN PRINT "The process is isobaric." REM Process takes place at a constant END IF

temperature.

pressure.

33. Table 4.3 gives the terms used by the National Weather Service to describe the degree of cloudiness. Write a program that requests the percentage of cloud cover as input and then displays the appropriate descriptor.

Table 4.3

Percentage of Cloud Cover

Descriptor

0-30 31-70 71-99 100

clear partly cloudy cloudy overcast

Cloudiness Descriptors

34. Table 4.4 shows the location of books in the library stacks according to their call numbers. Write a program that requests the call number of a book as input and displays the location of the book.

Table 4.4

Call Numbers

Location

100 to 199 200 to 500 and over 900

basement main floor

501 to 900 except 700 to 750

upper floor

700 to 750

archives

Location of Library Books

35. Write an interactive program that requests a month of the year and then gives the number of days in the month. If the response is February, the user should be asked whether or not the current year is a leap year.

4.3

SELECT CASE BLOCKS

145

36. Figure 4.5 shows some geometric shapes and formulas for their areas. Write a menu-driven program that requests the user to select one of the shapes, requests the appropriate lengths, and then gives the area of the figure.

Omiess en eke

al

es |

Parallelogram lems

Circle Ge. Figure 4.5

Kite (hee ow) fez

Areas of Geometric Shapes

ST. Write an interactive program that requests an exam score and assigns a letter grade with the scale 90-100 (A), 80-89 (B), 70-79 (C), 60-69 (D), 0-59 (F). (Test the program with the grades 84, 100, and 57.)

38. Computerized quiz show. Write a program that asks the contestant to select one of the numbers 1, 2, or 3. and then asks the corresponding question below. The program then should request the answer as input and tell the contestant if the answer is correct. 1. 2. 3.

Who developed the stored program concept? Who discovered the law of universal gravitation? Who first studied the force of attraction and repulsion between two charges?

(Note: The answers are von Neumann, Newton, and Coulomb.)

39. IRS informants are paid cash awards based on the value of the money recovered. If the information was specific enough to lead to a recovery, the informant receives 10 percent of the first $75,000, 5 percent of the next $25,000, and 1 percent of the remainder, up to a maximum award of $50,000.

Write a program that requests the amount of the recovery as input and displays the award. (Test the program on the amounts $10,000, $125,000, and $10,000,000.) Note: The source of this formula is The Book of Inside Information; Boardroom Books, 1993.

40. Write a program that displays the numbers and terms from Table 4.5, requests a number from 1 through 5 as input, and returns the definition of the requested term as output. A sample run of the program is: [run] 1.

algorithm

Enter a number A bug

is

2.

bug

from

a program

3.

input

1 through error.

4.

5: 2

output

5.

software

146

Decisions

ee 6

Term

Definition

1. algorithm

a finite series of steps leading to the solution of a problem

2. bug 3. input

a program error data obtained by a program from a device (such as keyboard or disk) during execution information produced by a program (usually displayed, printed, or recorded on a disk) computer programs

4. output 5. software

Table 4.5 Computer Terms

41. Table 4.6 shows significant inventions made each year from 1962 through 1966. Write a program that requests the year BASIC was invented and responds with either the message “Correct .” a significant invention made that year (if the answer is 1962, 1963, 1965, or 1966), or the message “You

are off by more than 2 years.” In the first two cases, the program should also give the name of the inventor. Year

Invention

Inventor

1962 1963 1964 1965 1966

Minicomputer Cassette tapes BASIC Word processor Noise reduction system

Digital Corporation Phillips Corporation Kemeny and Kurtz IBM Ray M. Dolby

Table 4.6 Significant Inventions

42. Table 4.7 contains information on several states. Write a program that requests a state and category (flower, motto, and nickname) as input and

displays the requested information. If the state or category requested is not in the table, the program should so inform the user. State

Flower

Nickname

California Indiana Mississippi New York

Golden poppy Peony Magnolia Rose

Golden State Hoosier State Magnolia State Empire State

Table 4.7

Motto

Eureka Crossroads of America — By valor and arms Ever upward

State Flowers, Nicknames, and Mottos

SOLUTIONS TO PRACTICE PROBLEMS 4.3 1. (a) Valid. These items are redundant since 1 and 4 are just special cases of IS < 10. However, this makes no difference in QBasic.

(b) Valid. These items are contradictory. However, QBasic looks at them one at a time until it finds an item containing the value of the selector. The action following this CASE clause will always be carried out. (c) Not valid; “2” is a string and the selector has numeric type.

2. Yes. However, the program on the right is clearer and therefore preferable.

Programming Projects

147

Chapter 4 Summary 1. The relational operators are , =, , =.

2. The principal logical operators are AND, OR, and NOT. 3. A condition is an expression involving constants, variables, functions, and

operators (arithmetic, relational, and/or logical) that can be evaluated to either true or false.

4. An IF block decides what action to take depending upon the truth values of one or more conditions. To allow several courses of action, the IF and ELSE

parts of an IF statement can contain other IF statements.

5. A SELECT CASE block selects one of several actions depending on the value of an expression, called the selector. The entries in the value lists must have the same type (string or numeric) as the selector.

Chapter 4 Programming Projects 1. The American Heart Association suggests that at most 30% of the calories in our diet come from fat. Whereas food labels give the number of calories and amount of fat per serving, they often do not give the percentage of calories from fat. This percentage can be calculated by multiplying the number of grams of fat in one serving by 9, dividing that number by the total number of calories per serving, and multiplying the result by 100. Write a program that requests the name, number of calories per serving, and the grams of fat per serving as input, and tells us whether the food meets the American Heart Association recommendation. A sample output is as follows: [run] Enter

name

Enter

number

Enter

grams

Lowfat

milk

contains

Lowfat

milk

exceeds

of

food:

Lowfat

of calories of

fat

per

milk

per serving: serving:

37.5% the

AHA

120

5

calories

from

fat.

recommendation.

2. Write a program to determine the real roots of the quadratic equation ax’ + bx +c = 0 (where a¥ 0) after requesting the values of a, b, and c. Insure that a is nonzero.

Note:

The

equation

has

2,

1, or O solutions

depending upon whether the value of b’ — 4ac is positive, zero, or negative. In the first two cases the solutions are given by the quadratic formula (—b + Vb? — 4ac ) / 2a.

148

Decisions

3. Write a program to find the day of the week for any date after 1582, the year

our current calendar was introduced. The program should: (a) Request the year and the number of the month as input. (b) Determine the number of days in the month. Note: All years divisible

by 4 are leap years, with the exception of those years divisible by 100 and not by 400. For instance, 1600 and 2000 are leap years, but 1700, 1800, and 1900 are not.

(c) Request the number of the day as input. The prompt should list the possible range for the number. (d) Determine the day of the week with the following algorithm. (1) Treat January as the 13th month and February as the 14th month of the previous year. For example 1/23/1986 should be converted to 13/23/1985 and 2/6/1987 should be converted to 14/6/1986. (2)

Denote the number of the day, month, and year by d, m, and y. Compute

w=d+t2m+ INT(.6 * (m+1)) + y + INT(y/4) —INT(y/100) + INT(y/400) + 2

(3)

The remainder when w is divided by 7 is the day of the week of the given date, with Saturday as the zeroth day of the week, Sunday the first day of the week, Monday the second, and so on.

Some sample outputs of the program are: [run] Year (xxxx)?

1776

Month (1 - 12)? 7 Day The

of Month (1 - 31)? 4 day of the week was Thu

[run] Year (xxxx)? 1987 Month (1 - 12)? 2 Day of Month (1 - 28 )? 28 The day of the week was Sat

Test the program with the following memorable dates in the history of the US. space program. On Tuesday, February 20, 1962, John Glenn became the first American to orbit the earth.

On Sunday, July 20, 1969, Neil Armstrong became the first person to set foot on the moon. On Saturday, June 18, 1983, Sally Ride became the first American woman to travel in space. 4. An electric circuit can be:

(a) Resistive (composed of resistors only) with impedance Z given by Z = R, where R is the equivalent resistance. (b) Capacitive (composed of capacitors only) with impedance given by Z = 1/(C- w), where w is the angular frequency and C is the equivalent capacitance.

Programming Projects

(c) Inductive

(composed

only)

of inductors

with

impedance

Z = L- w, where L is the equivalent inductance. (d) R-L series (composed of a resistor and an inductor

149

given by

in series) with

impedance given by Z = VR? + (L-w)’. (e) R-C series (composed of_a resistor and a capacitor in series) with impedance given by Z = VR? + 1/(C-w)’. (f) R-L-C series (consists of a resistor, a capacitor, and an inductor in series) with impedance given by Z = VR? + (L-w—1/(C-w))’. Write a program to calculate the impedance of a circuit. The program should request the type of circuit (from the list above), then the values of the components

of the circuit, calculate

the corresponding

impedance,

and

display the result. Some sample outputs of the program are: [run] Enter the type of circuit: inductive Enter inductance, angular frequency: .02, 100 The impedance Z of the inductive circuit is 2 Ohms. [run] Enter the type of circuit: resistive Enter resistance: 100 The impedance Z of the resistive circuit

is

100

Ohms.

Write a program to request a positive number n and the real and imaginary parts of a complex number as input, and display an nth root of the complex number. The program should convert the complex number to the polar form r(cos 8 + i- sin 8), with O < @ < 2, and then compute r!/™(cos(@/n) + i- sin(@/n)).

the nth root as

FICA taxes have a social security and a medicare component. In 1994, Social security taxes are paid at the rate of 6.2 percent on the first $60,600 of earnings in a year. Medicare taxes are paid at the rate of 1.45 percent on total earnings. Write a program to request this year’s total earnings prior to

the current pay period and the earnings for the current pay period for an employee, and then calculate the FICA tax. . Write a program to solve the system of linear equations ax + by =e cx + dy =f where the values of a, b, c, d, e, and f are stored in DATA statements. The

program should report if there are one, none, or infinitely many solutions, and should display all solutions. Note: The program has a unique solution when ad — bc # 0. Infinitely many solutions can be described as (x, mx + 1) for specific values of m and r.

Genetics. The color of a guinea pig’s coat is determined by a single pair of genes. Two possible coat colors are black and brown. Black is dominant to brown, which means that a guinea pig which inherits a gene for black (B) from one parent and a gene for brown (b) from the other will have a black

coat. The recessive gene will determine the color only if both parents pass on the recessive gene. Hair length is also controlled by a single pair of genes; short hair (S) is dominant to long hair (s). Every guinea pig inherits two

150

Decisions

genes for each trait, but can pass on only one gene for each trait. This gene must be among those received from the parents. For example, a guinea pig with the genetic makeup “Bbss” can pass on either a black or brown coat color, but must pass on long hair. The offspring may or may not have long hair, depending on the hair length gene from the other parent. Write a program that requests the genes from a male and female adult guinea pig in the form of two four-character strings (such as “BbSs” and “bbSs”), requests

the hair color and hair length of a baby guinea pig and determines if the baby could be an offspring of the adults.

Repetition

-333rore

al

point values jage Pymt), $300,1 | Over

this

Hd

name

Print

3

THEN

INT

ELSE

WEND LPRINT

EN

aaa

MDESS$

tt Ga

G

ptal of pr ter fils ile e from a

’ 5 |

i

e(K) ae" > MUPC (K)

WHILE P IF P

i ed items, purchase ii

priceof pi ‘Array numbe-

"To hold ru “UPC numb ‘Price fr’ PC, descri AS #1 MPRI

T2090 LET TO eo LET MUP e O LET MPR d and prin REM -OPEN "“LEDAT” FOR I UPCS,. MDE INPUT

value

bank?,

(K)

: S PCS' ,PU (J) C PUP

: SWAP |

S a= LET K =

3, | point

QO N-1 +1 TO N-1 > PU $(J)

FOR J FOR IF NEXT NEXT J RETURN

INP

es ole ig

Se

CLOSE ARETURN

WAM

a

} i\t )

\\

determine

GE

,

POLE

LE

es

Sonic

oroaram tne

EE

apmold”

HR

SCnrmeLldear «=

M4 ,

if

Mun minim

ALG interactive 1@ AMSHOrS are

PE ashe

CE

cl

4

Xe

PUL TONG i MOUNT MLM

#

oh

title:

REL

,

APE

PSL

iy BOF #

7%

é

D

IE

i

cs

") vou

Do i

iE

Bad2 SRS a é

Ee

quality a

for

a ?

ba; s

.

152

Repetition

5

1 DO LOOPS A loop, one of the most important structures in QBasic, is used to repeat a sequence of statements a number of times. At each repetition, or pass, the statements act upon variables whose values are changing. The DO loop is one of the most important structures in QBasic. It repeats a sequence of statements either as long as or until a certain condition is true. A DO statement precedes the sequence of statements and a LOOP statement follows the sequence of statements. The condition, along with either the word WHILE or UNTIL, follows the word DO or the word LOOP. When QBasic executes a DO loop of the form DO

WHILE

condition

statement (s) LOOP

it first checks the truth value of condition. If condition is false, then the statements

inside the loop are not executed and the program continues with the line after the LOOP statement. If condition is true, then the statements inside the loop are executed. When the statement LOOP is encountered, the entire process is repeated beginning with the testing condition in the DO WHILE statement. In other words, the statements inside the loop are repeatedly executed as long as the condition is true. Figure 5.1 contains the pseudocode and flowchart for this loop.

DO WHILE condition is true Processing step(s) LOOP

Is the condition true?

Execute statements within the loop

Execute statements that follow

the loop

Figure 5.1

Pseudocode and Flowchart for a DO Loop

No

5. Pf (DOLOOPS”

EXAMPLE

1

SOLUTION _

1153

Write a program that displays the numbers from | through 10. The condition in the DO loop is num 1981 PRINT “Earlier than that. The first successful IBM PC clone, " PRINT "the Compaq Portable, appeared in 1983." END SELECT PRINT LOOP UNTIL year = 1981 END

(Assume the first response is 1980 and the second response is 1981.)

"

5:1

6.

REM

Simulate

INSTR,

search

for

a

letter.

INPUT "Enter a word: ", word$ INPUT "Enter a letter: ", letter$ LET counter = 0 LET oldLetter$ = " " DO WHILE (oldlLetter$ letter$) AND counter

LET

= counter

+

DOLOGES

(counter

1) AND (a < 3) 20. UNTIL (state$ = “motion”) AND (acceleration = 5)

21. UNTIL NOT (n = 0)

22. WHILE (a$ = “capacityCharging”) AND (energy < 7) In Exercises 23 and 24, write a simpler and clearer program that performs the same task as the given program. 23. INPUT

num

PRINT

num

INPUT

num

PRINT

num

INPUT

num

PRINT

num

END

53) DO LOOPS,

24. REM

Calculate

REM LET DO

the

number

n of

revolutions

per

165

minute

of a generator loopNum = 0 IF loopNum >= 1 THEN INPUT "Do you want

to continue

(Y/N)";

answer$

ELSE

LET END

IF

answer$

= "Y"

IF

(answer$

= "Y")

OR

(loopNum

= 0)

THEN

INPUT frequency LET n = 60 * frequency LET loopNum = loopNum + 1 PRINT

END

LOOP

n

IF

UNTIL

answer$

"Y"

END

25. Write a program that requests a temperature between 0 and 100 degrees Celsius and converts the temperature to Fahrenheit. If the response is not between 0 and 100, the request should be repeated until a proper response is given. (Note: The formula f = (9/5)c + 32 converts Celsius to Fahrenheit.)

26. According to Newton’s law of motion, the resultant of all of the forces acting on a body of mass m is R=ma

where a is the acceleration of the body. Consider a body of mass m subjected to its weight w = mg (g is the acceleration of gravity) and a frictional force F (due to air resistance) given by F=kyv

where v is the speed of the body and k is a constant depending on the dimensions of the body. The equation of motion is mg — kv = ma

Write a program to solve the above equation (find v) where m, a, g, and k are supplied with INPUT statements. After solving the equation, ask the user if he or she wants another equation solved. 27. Write a program that repeats the question “D’you know the capital of Alaska?” until the correct answer is given. The program should display the statement, “It rhymes with D’you know.” when an incorrect answer is given. 28. Write a program to forecast the weather in Oregon. The program should request input with the prompt “Can you see the mountains (Y/N)?” The program should display “It is going to rain.” or “It is raining.” depending upon whether the first letter of the response is Y (or y) or N (or n), respectively. If the first letter of the response is not Y, y, N, or n, the request should be repeated until a proper response is given.

164

Repetition

Zo A car’s computer can determine the number of gallons of gasoline in the

tank and sense whether the driver’s seatbelt is fastened and the doors are closed. The computer will not allow the car to be shifted out of “Park” if either the driver’s seatbelt is not fastened or any door is open. If the tank contains less than two gallons of gasoline, the message “Get gas.” is displayed. Write a program to simulate the operation of the computer. A sample output 1S:

{run] Is the driver's seatbelt fastened Are all doors closed (Y or N)? Y¥ Please Is

the

fasten

your

driver's

gallons

How

many

You Get

may proceed. gas.

N

N)?

Y

seatbelt.

seatbelt

of

(Y or N)?

gas

fastened

are

in

the

(Y

or

tank?

1

30. Write a program to find the first integer whose cube is greater than 3000. Sls Write a program that asks the user to enter positive numbers into the computer until the product of the numbers exceeds 400. The program should then display the highest number. Sy” There is a legend that King Shirham of India wanted to reward his grand vizier Sissa Ben Dahir for inventing the game of chess. When asked what reward he wanted, Sissa Ben asked for 1 grain of wheat on the first square of the board, 2 on the second, 4 on the third, and so forth, doubling the amount of grains on each successive square. King Shirham quickly found that the amount of wheat in the request would be more than his country could possibly produce. Write a program that uses a loop to calculate on which of

the 64 squares of the chessboard the total number of grains would exceed (a) one million; (b) one billion; (c) one trillion.

a3. Write a program to display all the numbers between | and 100 that are perfect squares.

34. The population of Mexico City is currently 14 million people and growing at the rate of 3 percent each year. Write a program to determine when the population will reach 20 million. 35, Write a program to solve the equation ax + b = c, where the numbers a, b, and c are supplied via INPUT statements. Allow for the case where a is 0. If so, there will either be no solution or every number will be a solution. After solving each equation, ask the user if he or she wants another equation solved. 36. Write a program that requests a word containing the two letters r and n as input and determines which of the two letters appears first. If the word does not contain both of the letters, the program should keep requesting words until one does. (Test the program with the words colonel and merriment.)

521)

DOLOOPS:

— 165

37. The coefficient of restitution of a ball, a number between 0 and 1, specifies

how much energy is conserved when a ball hits a rigid surface. A coefficient of .9, for instance, means a bouncing ball will rise to 90 percent of its initial height after each bounce. Write a program to input a coefficient of restitution and a height in meters and report how many times a ball bounces before it rises to a height of less than ten centimeters. Also report the total distance traveled by the ball before this point. The coefficients of restitution of a tennis ball, basketball, super ball, and softball are .7, .75, .9, and .3, respec-

tively. In Exercises 38 through 43, write a program to solve the stated problem.

38. Savings Account. Fifteen thousand dollars is deposited into a savings account paying 5 percent interest and $1000 is withdrawn from the account at the end of each year. Approximately how many years are required for the savings account to be depleted? 39. Rework Exercise 38 for the case where the amount of money deposited initially is input by the user and the program computes the number of years required to deplete the account. (Note: Be careful to avoid infinite loops.)

40. The simplest semiconductor device is a p—n junction, or diode, made of Germanium or Silicon doped with a particular type of impurity. The current-voltage relationship in an ideal diode is described by

[Sh (ei

1)

I is the current that flows through the diode (in amperes). 1: is the saturation current (in amperes), L. =10°

amperes.

v is the voltage across the diode (in volts). q is the electron charge, q = 1.6 - 107? coulombs k is Boltzmann’s constant, k = 1.38 - 10773 joules / °K T is the temperature of the junction (in °K)

With T = 293°K, calculate and display I as v varies from —.2 volts to 1 volt in steps of .1. 41. One thousand dollars is deposited into a savings account, and an additional $1000 is deposited at the end of each year. If the money earns interest at the rate of 5 percent, how long will it take before the account contains at least

one million dollars? 42. The change, 6, in the dimensions of a block of material of length L is given by

6=a-TL where T is the change in temperature (in degrees Celsius) and o is the coefficient of thermal expansion which is a property of the material. For a block of aluminum of length 3.0 and a = 23 - 10° / °C, calculate 8 for different values of T (T = 10, 15, 20, .. .). Stop when 6 exceeds 4 - 103

meters and display the corresponding temperature. 43. A person born in 1980 can claim “I will be x years old in the year x squared.” Determine the value of x.

166

Repetition

t. ar ch ow fl the to g in nd po es rr co m ra og pr a e it wr 45, d In Exercises 44 an d an ut inp as | an th r ate gre r ege int an ts ues req 5.3 44. The flowchart in Figure y onl its if e im pr is er mb nu A : te No s. er mb nu e im pr factors it into a product of .) 139 d an 0 66 s er mb nu the th wi m ra og pr the st (Te . elf its d an 1 factors are

Get two

Get integer

pos. integers

N>1

M and N

Set F=2

No

Yes

No

Does

Yes

F divide N ?

Increase

F by 1

Set N = N/F

End

Figure 5.3

Prime Factors

Figure 5.4

Greatest Common Divisor

45. The flowchart in Figure 5.4 finds the greatest common divisor of two positive integers input by the user. (The greatest common divisor of two positive integers is the largest integer that divides both of the numbers.) Write a program that corresponds to the flowchart.

5.2

PROCESSING LISTS: OF DATA WITH DOLOOPS

167

46. After the engine of a moving motor boat is turned off, the speed of the boat decreases as it continues to move across the water. If the boat’s speed in miles/hour when

the motor is turned off is initSpeed, then its speed after

moving distance feet is given by speed = initSpeed - Exp(—2 - (distance / 5280)) (a) Write a function that accepts a boat’s initial speed and the distance it

has travelled since the motor was turned off as input, and computes its speed at that distance. (b) Suppose to safely ground a boat on the beach, it should be moving between 2 and 5 miles/hour. Use the function in (a) to write a program

that requests the initial speed of a boat and outputs the distance from the beach the motor should be turned off in order to drift safely to the beach. Hint: Use a loop to increase the distance until the function yields a value in the desired range.

SOLUTIONS TO PRACTICE PROBLEMS 5.1 1. As arule of thumb, the condition is checked at the bottom if the loop should be executed at least once.

2. Either precede the loop with the statement LET continue$ = “Yes” or change the first line to DO and replace the LOOP statement with LOOP UNTIL continue$ “Yes”.

5

vy, PROCESSING LISTS OF DATA WITH DO LOOPS One of the main applications of programming is the processing of lists of data. DO loops are used to display all or selected items from lists, search lists for specific items, and perform calculations on the numerical entries of a list. This

section introduces several devices that facilitate working with lists. Counters calculate the number of elements in lists, accumulators sum numerical values in lists, flags record whether certain events have occurred, and trailer values

indicate the ends of lists. Nested loops add yet another dimension to repetition. Trailer Values

The data to be processed are retrieved by a DO loop either from DATA statements or from the user with INPUT statements. In order for the loop to know when all the data have been read, special data called trailer values or sentinels are added to the end of the list. Commonly used trailer values are —1 and EOD, which stands for “End of Data.” Trailer values should not be possible responses for processing. For instance, if a loop calculates a bowling score, 0 is not a good trailer value since the user might enter O to represent a gutter ball.

168

Repetition

EXAMPLE

1

The s. ion ent inv nt ica nif sig e som of es dat the ys pla dis m gra pro ing low fol The ue val ler trai t firs The s. ent tem sta TA DA in ned tai con are s ion ent inv dates and is , EOD ue, val ler trai ond sec The d. rea is —1 il unt eat rep will is —1. The loop needed to have something

to assign to invention$

on the last execution of

READ. REM

Dates

of

significant

inventions

CES READ dateOfInvention, invention$ DO WHILE dateOfInvention -1 PRINT dateOfInvention, invention$ READ dateOfInvention, invention$ LOOP REM --- Data: date, invention DATA

1100,

rocket

DATA

1410,

wire

DATA

1620,

submarine

DATA

1948,

velcro

DATA DATA END

1964, BASIC -1, EOD

[run] 1100

rocket

1410

wire

1620

submarine

1948

velcro

1964

BASIC

The program in Example 1 illustrates the proper way to process a list of data having a trailer value. The DO loop should be tested at the top. The first item of data should be obtained before the DO statement and used to determine whether the loop should be entered. The loop begins by processing the data and then requests the next piece of data just before the LOOP statement. This method of processing a list guarantees that the trailer value will not be processed. Figure 5.5 contains the pseudocode and flowchart for this technique.

EXAMPLE

SOLUTION

2

Modify the program in Example | to search the list of significant inventions for an invention specified by the user. If the invention does not appear in the list, so notify the user.

For starters, we should begin with an INPUT statement to request the sought invention. We want to keep searching as long as there is no match and we have not reached the end of the list. Therefore, the condition for the DO WHILE statement is a compound logical expression with the operator AND. After the last pass through the loop, we will know whether the invention was found and be able to display the requested information.

5.2

PROCESSING LISTS OF DATA WITH DO LOOPS

Get first item DO WHILE item is not the trailer value Process the item Get the next item

LOOP Is item different from the trailer value?

Process the item

Execute

statements following loop

Figure 5.5 REM CLS

Look

INPUT READ

Pseudocode and Flowchart for Processing a List with Trailer Value for

a specific

"Invention";

inventToFind$

dateOfInvention,

DO WHILE READ

invention

invention$

(inventToFind$ dateOfInvention,

invention$)

invention$

LOOP IF dateOfInvention = -1 THEN PRINT "Invention not found." ELSE PRINT dateOfInvention, invention$ END IF REM

---

Data:

date,

DATA

1100,

rocket

DATA

1410,

wire

DATA

1620,

submarine

DATA DATA DATA END

1948, velcro 1964, BASIC -1, EOD

"Invention

invention

"Date,

AND

to

search

invention

(dateOfInvention ‘Date,

for

invention

-1)

in

list

169

170

Repetition

[run] Invention?

submarine

1620

submarine

[run] Invention? Invention

airplane not

found.

Nested Loops The statements inside of a DO loop can consist of another DO loop. Such a configuration is referred to as a nested loop and is useful in repeating a single data processing routine several times.

EXAMPLE 3

Modify the program in Example 2 to allow the user to look up as many inventions as desired.

SOLUTION

The statements inside the DO WHILE loop will be used to look up inventions as before. At least one pass through the outer DO loop is guaranteed and passes will continue as long as the user responds “Y”. REM Look for specific inventions CLS DO RESTORE INPUT "Invention"; inventToFind$ READ dateOfInvention, invention$

DO WHILE READ

(inventToFind$

dateOfInvention,

invention$)

‘Invention ‘Date,

AND

invention$

to

search

invention

(dateOfInvention ‘Date,

for

-1)

invention

LOOP IF dateOfInvention = -1 THEN PRINT "Invention not found." BESE

PRINT END

dateOfInvention,

invention$

IF

INPUT "Do you want to look up another LOOP UNTIL response$ "Y" REM --- Data: date, invention DATA 1100, rocket DATA

1410,

wire

DATA

1620,

submarine

DATA

1948,

velcro

DATA

1964,

BASIC

DATA

-1,

invention

(Y/N)";

EOD

END

[run] Invention?

velcro

1948

Do you

velcro

want

Invention?

to

up

another

invention

(Y

N)?

Ni

up another

invention

(Y or N)?

N

or

wire

1410

Do you

look

wire

want

to

look

response$

in

list

PROCESSING LISTS OF DATA WITH DOLOOPS

5.2

171

Counters and Accumulators

A counter is a numeric variable that keeps track of the number of items processed. An accumulator is a numeric variable that totals numbers.

EXAMPLE 4

Write a program to count and find the value of coins listed ina DATA statement.

SOLUTION

REM

How much

change

LET

numCoins

= 0

LET

sum

do you

have?

CLS

READ

= 0

num

DO WHILE

num

LET

numCoins

LET

sum

READ

-1 = numCoins

= sum

+

1

+ num

num

LOOP PRINT REM

"The ---

DATAM

value

Data:

wel

of

the";

numCoins;

"coins

is";

sum;

"cents."

coin

5 al Ons

2

Om

END

[run] The

value

of

the

6

coins

is

52

cents.

The value of the counter, numCoins, was initially

0 and changed on each

execution of the loop to 1, 2, 3, 4, 5, and finally 6. The accumulator, sum, initially had the value 0 and increased with each execution of the loop to 1, 2, 7, 17, 27,

and finally 52.

Flags A flag is a variable that keeps track of whether a certain event has occurred. Typically, it is initialized with the value O and then assigned a nonzero value when the event occurs. It is used within a loop to provide information that will be taken into consideration after the loop has terminated. The flag also provides an alternate method of terminating a loop.

EXAMPLE 5

The following program counts the and then reports whether the words of the loop, a word is compared to called orderFlag, is initially assigned words is out of order. The technique 7 when we study sorting. Note: The

number of words in the DATA statements are in alphabetical order. In each execution the next word in the list. The flag variable, the value 0 and is set to 1 ifa pair of adjacent used in this program will be used in Chapter statement in line 5 is a device to get things

started. Each word must first be read into the variable word2$. In fact, wordCounter is incremented only when word2$ gets a non-sentinel value. words.

REM

Count

CLS LET

orderFlag

= 0

Are

they

in

alphabetical

order?

172

Repetition

= 0

LET wordCounter

LET wordl$ = "" READ word2$ DO WHILE word2$ "EOD" LET wordCounter = wordCounter IF word1$ > word2$ THEN LET orderFlag = 1 END IF LET word1$ = word2$ READ word2$ LOOP "The

PRINT

number

IF orderFlag = 0 THEN PRINT "The words are

ELSE PRINT END

words

"The

is";

of words

+ 1

wordCounter

in alphabetical not

are

in

order."

alphabetical

order."

IF

REM --- Data: DATA cambist,

winning words in U.S. National Spelling Bee croissant, deification, hydrophyte, incisor

maculature,

DATA

macerate,

narcolepsy,

shalloon,

EOD

END

[run] The number of words is 9 The words are not in alphabetical

EXAMPLE 6

order.

Write a program to calculate the average of exam grades input by the user. The program also should indicate whether any student received a perfect score.

SOLUTION _ The following program uses the variable numScores as a counter, the variable sum as an accumulator, and the trailer value —1. REM

Calculate

average

score

CLS REM Display instructions PRINT "Enter the scores one at a time. After all of the" PRINT "scores have been reported, enter the number -1." REM Input scores from the user LET numScores = 0 LET sum = 0 LET perfectFlag = 0 INPUT "Enter a Score: ", score DO WHILE score -1 LET numScores = numScores + 1 LET

sum

= sum

+ score

IF score = 100 THEN LET perfectFlag

END IF INPUT "Enter LOOP

a Score:

= 1 ",

score

PROCESSING LISTS OF DATA WITH DO LOOPS

5.2

REM

Compute

and

REM

Announce IF numScores

display

if >=

there

IF

average

are

any

perfect

scores

1 THEN

LET average PRINT

173

= sum / numScores

"The

average

score

is";

average

perfectFlag = 0 THEN PRINT "No perfect score." EESE

PRINT END IF END

"At

least

one

perfect

score."

IF

END

[run] Enter

the

scores

scores

have

one

been

Enter

a score:

80

Enter

a score:

Enter

a score:

90 82

Enter

a score:

Enter

a score:

The

No

average

perfect

at

a time.

reported,

enter

After the

all

of

number

the -1.

88 -l

score

is

85

score.

In Example 6, the value of the counter, numScores, was initially 0 and changed on each execution of the loop to 1, 2, 3, and finally 4. The accumulator,

sum, initially had the value 0 and increased with each execution of the loop to 80, 170, 252, and finally 340. The flag, perfectScore, was initially 0 and never changed. After the loop was terminated, the average was calculated by dividing

340 by 4.

Loops in Mathematics Suppose

the mathematical

function f(x) is defined and continuous on the

interval [a, b], and f(a) has a different sign than f(b). (See Figure 5.7.) Then the equation f(x) = 0 must have a solution between a and b. That is, there must exist a number c between a and b with f(c) = 0. Such a number c is called a zero of the

function. The flowchart in Figure 5.6 describes an algorithm, known as the bisection method, for finding c. At each iteration, the length of the subinterval

containing c is halved. Halving continues until the subinterval reaches a certain tolerance length (such as .00001) or until c is found exactly (an unlikely event). Because single-precision numbers are only accurate to 7 significant figures, the choice of an appropriate tolerance level depends on the magnitude of the zero. For instance, .1 is an appropriate tolerance level if c is near 100,000,000, and 10-3! is appropriate if c is very close to 0. In general, .00001 is a good tolerance level for medium-sized values of c.

174

Repetition

Figure 5.6 Flowchart for the Bisection Method

EXAMPLE

7

Figure 5.7 A Function with a Zero in the Interval [a, 5]

Write a program to find a zero of the function e*— x— 4. This function is graphed in Figure 5.7. REM

REM

The

Bisection Method Approximate a zero of a function

REM values CLS

a and b, where f(a)

f(x)

and f(b)

between

the

have different

user

signs

supplied

PROCESSING LISTS OF DATA WITH DOLOORS

>.2

“175

DEE ENT (x) = EXP(x) = x = 4 INPUT "Enter a tolerance level (such as .00001): ", tolerance REM Guarantee that the tolerance level is not too smal] IF tolerance 0 = total

LET total READ num LOOP PRINT REM

total --- Data:

DATA

5,

2,

+ num

numbers

6,

-1

END

2. REM Display

list of noble gases

READ gas$ DO WHILE gas$ PRINT gas$ READ gas$ LOOP REM

---

DATA

Data:

"EOD"

noble

Helium,

Neon,

gases Argon,

Krypton,

Xenon,

Radon,

EOD

END

3. READ city$, DO

WHILE

IF

pop

pop

city$

>=

"EOD"

7 THEN

PRINT city$ END

IF

READ city$ LOOP REM --- Data: DATA

San

DATA

Boston,

DATA

Chicago,

DATA

New

DATA

EOD,

city,

Francisco,

population

(in millions)

5.6

4 8

York,

17.7

0

END

4. REM READ

Display

some

numeric

constantName$,

DO WHILE READ

value,

constantName$

PRINT

constants.

constantName$;

constantName$,

unit$

"EOD"

" =";

value;

value,

unit$

name,

value,

unit$

LOOP REM

---

Data:

constant

DATA

"Speed

of

DATA

"Planck's

DATA

"Avogadro's

DATA END

EOD,

-1,

light",

2.9979E8,

constant",

EOD

number",

unit

"meters

6.626E-34,

6.022E23,

per

second"

"joule-seconds"

"molecules

per

second"

177

178

Repetition

5. READ

sentence$ was

' flag tells if the loop LET flag = 0 DO WHILE LEN(sentence$) < 20 LET flag = 1 LET sentence$ = sentence$ + sentence$

executed

LOOP

IF flag = 1 THEN PRINT sentence$ BESE PRINT "Loop not executed." END IF REM --- Data: sentence DATARS Is thinkel cane. END

6. READ fruit$ DO WHILE fruit$ "EOD" LET firstLetter$ = LEFT$(fruit$, 1) PRINT TAB(3); firstLetter$ DO WHILE LEFT$(fruit$, 1) = firstLetter$ PRINT fruit$ READ fruit$ LOOP PRINT LOOP REM --- Data: fruits DATA

Apple,

Apricot,

DATA

Blueberry,

Avocado,

Grape,

Lemon,

Banana Lime,

EOD

END

7. REM Display READ DO

list of numbers

num

WHILE READ

num

-1

num

PRINT

num

LOOP REM --DAMAW25 END

Data: numbers 35) S555) 0-2

8. INPUT "Animal"; animal$ READ creature$, groupName$ DO WHILE (creature$ animal$) READ creature$, groupName$

AND

(creature$

"EQD")

LOOP

IF groupName$ PRINT

= "*"

"Animal

THEN not

found."

BESE

PRINT END

IF

REM

---

DATA

"A group

Data:

lion,

of

animal,

pride,

duck,

";

animal$;

name

"s

is

called

a ";

of group

brace,

END

(Assume the response is duck.)

bee,

swarm,

EOD,

*

groupName$

PROCESSING LISTS OF DATA WITH DOLOOPS_

5.2

9. READ word$ DO WHILE IF

word$

"EOD"

LEFT$(word$,

1)

LET cWord$ END IF READ word$ LOOP PRINT cWord$ REM

---

Data:

=

“c”

THEN

= word$

saying

DATA

time,

is,

a,

DATA

Heraclitus,

child,

idly,

moving,

counters,

in,

a,

game

EOD

END

10. REM Determine

the maximum

REM

representing

REM

of

certain

of a set of values

experimental liquids

at

20

values degrees

of

surface

tension

Celsius.

LET

max = 0 READ value DO WHILE value -1 LET rowMax = 0 LET value = 0 DO WHILE value -2 IF value > rowMax THEN LET rowMax = value END IF READ value LOOP PRINT

IF

rowMax

rowMax

> max

LET

=

max

THEN rowMax

END IF READ value LOOP PRINT

max

REM

---

REM

tetrachloride,

Benzene,

REM

soap

and

Data:

surface

solution,

DATAG2275.4 26205, 25-97 DATA 63.1, 465, 32, -2 DATA 25,°72-9,.-c, —1 END

In Exercises 11 through 11. READ DO

num

WHILE PRINT

READ REM

DATA END

---

num

-1

num

num Data:

numbers

5505.05,

15-2

tension water.

of

Ethyl

Alcohol,

Carbon

Glycerine,

Mercury,

olive

-2

and

-1

are

-2

14, identify the errors.

trailers

oil, values

179

180

Repetition

12. LET flag = 0 DO WHILE flag 1 INPUT "Enter radius: ", radius IF radius * radius < 0 THEN LET flag = 1 END IF LOOP END

of some U.S.

names

13. REM Display

Presidents

DO

READ name$ PRINT name$ LOOP UNTIL name$ --- Data: DATA Lincoln, REM

= "EOD" presidents Washington,

Kennedy,

Reagan,

EOD

END

14. READ num DO WHILE 1 < num < 5 PRINT "The period of

pendulum

is";

num;

"seconds."

num

READ

LOOP DATA

the

3,

2,

4,

7,

2

END

15. Write an interactive program to find the largest of a collection of positive numbers. The user should be prompted to provide numbers until the response —1 is given, at which time, the largest number should be displayed. (Test the program with the collection of numbers 89, 77, 95, and 86.)

16. Table 5.1 contains some SI derived quantities and their units and symbols. Write a program that requests a symbol and gives the corresponding quantity and its unit. The user should be informed if the unit is not in the table.

Table 5.1

Quantity

Unit

Symbol

frequency force pressure power inductance energy capacitance

hertz newton pascal watt henry joule farad

Hz N Pa W H J E

SI units

17. Write an interactive program that asks the user to INPUT a distance in miles and converts it to kilometers. The process should be repeated until the user signs off by entering —1. Note: 1 mile is approximately 1.6 kilometers. (Test the program with the values 3 and .625.)

PROCESSING LISTS OF DATA WITH DOLOOPS

5.2

181

18. Write a program that allows the user 10 tries to answer the question “Which USS. President was born on July 4?” After three incorrect guesses the program

should give the hint “He once said, ‘If you don’t say anything, you won’t be called upon to repeat it.”” After seven incorrect guesses the program should give the hint “His nickname was ‘Silent Cal.’” Note: Calvin Coolidge was born on July 4, 1872. 19: Table 5.2 shows the different grades of eggs and the minimum weight required for each classification. Write an interactive program in which the user repeatedly inputs the weight of an egg and obtains the appropriate grade. The user should enter a negative number to terminate the process. (Note: Eggs weighing less than 1.5 ounces cannot be sold in supermarkets.) Figure 5.8 shows a typical output of the program.

Grade

Weight

(in ounces)

Weight The

Jumbo Extra Large Large Medium Small

Table 5.2

BS Dio 2 ei i

Grades of Eggs

of egg

grade

is

in ounces? Extra

2.3

Large.

Weight of egg in ounces? Send it to the bakery.

1.4

Weight

-1

Figure 5.8

of egg

in ounces?

Output for Exercise 19

20. When n capacitors C,, C), ..., C,, are connected in parallel in a circuit, the equivalent capacitance is defined as

Coie Cl

Ort

ae Ge

Consider a circuit with capacitors in parallel. Write a program to request the capacitances as input and display the values of C.,, Cray and C,,i, where

C

max

= C,,(1 + precision)

and

CG min ~ eat — precision)

The precision and the values of the capacitances C,, C), ..., C,, should be entered as input one at a time. The following is a typical output of the program. [run] Enter

-1

Enter Enter Enter Enter Enter

the precision: a capacitance: a capacitance: a capacitance: a capacitance:

Ceq

10.5

=

when

all

capacitances

have

been

entered.

.01 1 3.5 6 -1

microfarad

Cmax = 10.605 microfarad Cmin = 10.395 microfarad

le Table 5.3 contains the meanings of some abbreviations doctors often use for prescriptions. Write a program that requests an abbreviation and gives its meaning. The user should be informed if the meaning is not in the table.

182

Repetition

Meaning

Abbreviation

before meals needed as ly free twice daily a drop at bedtime four times a day

ac ad lib bid gtt hs qid Physicians’ Abbreviations

Table 5.3

Naps. Consider the list of the three radioactive elements Plutonium, Radon, and Uranium. The following program asks the user for an additional radioactive element and then displays the four elements in alphabetical order. REM

Merge

a new

radioactive

element

into

an

ordered

list

CES INPUT

“Enter

a new

radioactive

element:

READ element$ DO WHILE (element$ = "A") AND (letter$ max then k2 = max (e) Increment n by 2 and repeat from step (b) if possible. Be sure to make provisions for handling the last array element if there are an even

number of array indices.

7.2,

USING ARRAYS

301

32. A branch point (or a node) in an electric network is a point where three or more conductors are joined. Kirchoff’s first rule states that the algebraic sum of the currents flowing towards any branch point is zero. The currents (given in Table 7.7) at a node are stored in the array current(). Write a program to calculate and display the sum of the entries with odd subscripts in the array.

Current

Table 7.7

1 See 0 Sie 2-09

Oi

1205

ie

0

ea

Currents at a Branch Point

33. Write a program to dimension an array with the statement DIM state$(1 TO 50) and maintain a list of certain states. The list of states should always

be in alphabetical order and occupy consecutive elements of the array. The options for this menu-driven program should be as follows: (a) Request a state as input and insert it into its proper position in the array. (If the state is already in the array, so report.) (b) Request a state as input and delete it from the array. (If the state is not in the array, so report.)

(c) Display the states in the array. (d) Quit.

34. Write a program that requests a sentence one word at a time from the user and then checks whether the sentence is a word palindrome. A word palindrome sentence reads the same, word by word, backward and forward (ignoring punctuation and capitalization). An example is “You can cage a swallow, can’t you, but you can’t swallow a cage, can you?” The program should hold the words of the sentence in an array and use procedures to obtain the input, analyze the sentence, and declare whether the sentence is a word palindrome. (Test the program with the sentences, “Monkey see, monkey do.” and “I am; therefore, am I?”)

3D. Write a program to find the number of students scoring above the average grade on an exam, where the grades are input one at a time with the grade of —1 as trailer value. (Assume the class contains at most 100 students.) Use a procedure to input the grades and a function to calculate the number. Note: The procedure must have two parameters, an array parameter for the grades and a numeric parameter for the number of elements of the array that have been assigned values.

36. Table 7.8 displays the approximate speed (in feet per second) of sound waves in various substances (at room temperature). Write a program to READ the information into parallel arrays and print it out with the units converted to miles per hour (1 ft/sec = 0.682 mph). The program should still work if more data is added to the DATA statements.

302

Arrays

Substance

Speed (ft/sec)

Air

1,126

Hydrogen Carbon dioxide

4,315 877 4,820 16,800 11,500 12,960

Water Steel Brass Granite

Table 7.8 Speed of Sound in Various Substances

OTE Suppose an array of 1000 names is in ascending order. Write a procedure or portion of a program to search for a name input by the user. If the first letter of the name is N through Z, then the search should begin with the 1000th element of the array and proceed backwards. 38. Table 7.9 shows two lists of minerals and their hardnesses based on Moh’s hardness scale. Write a program to input each list into an array (the number of items in each list is unknown) and then create a third array by merging the lists, in order of hardness.

Hardness 1 j} 3 4 5 6 7 8 9 10 Table 7.9

Mineral Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond

Hardness LS 2.) 3 ie) oy) 6.5 7 [ibe 8 9

Mineral Graphite Halite Mica Malachite Turquoise Pyrite Garnet Tourmaline Emerald Sapphire

Moh’s Hardness Scale for Two Sets Of Minerals

39. The array a() has been dimensioned to have range | to 4, and values have been assigned to a(1) through a(4). Write code to reverse the order of these values in the array.

40. Modify Exercise 39 to reverse an array of arbitrary length. 41. Write a program that requests a sequence of numbers from the user and then reports whether the numbers are in increasing order, decreasing order, or neither. 42. Write a program to accept ten words to be input in alphabetical order and store them in an array. Then accept an eleventh word as input and store it in the array in its correct alphabetical position.

USING

7.2

ARRAYS

303

43. We define the scalar product, or inner product, of two vectors (in this case, arrays) p() and q() of dimension n as the sum of the products of correspond-

ing array elements, that is scalar product = p(1)q(1) + p(2)q(2) +... + p(n)q(n) Write a function to compute the inner product when p(), q() and nare passed as arguments.

44,

The center of mass of a system of n particles of mass m,, m),..., mM, is specified by its coordinates x and y in the plane: m= (myer

mpx9-4+ ... tom, x) | Gin, tm

+... oP My)

y = (myyy + myy2 +... + myy,) / (my + m2 +... + My) where x; and y, are the coordinates of the particle of mass m,. Write a program to:

(a) INPUT the masses and the x- and y-coordinates into parallel arrays m(), x(), and y().

(b) Calculate the sum m, + m) +... +m, and store it in the variable sum. (c) Calculate the scalar products m- x andm- y (d) Calculate the coordinates x and y of the center of mass. The value of n should be entered with an INPUT statement. Test the program with n = 3, m, = 20 g, m, = 50 g, m; = 60 g, (x, y,;)=(0,0),

(xX), ¥2)=(20,0), and (x3, y3)=(3,15). 45. Table 7.10 gives the boiling points of certain substances at normal atmospheric pressure. The program below displays the substances with a boiling point higher than that of water. Modify this program to display only the substance with the highest boiling point. REM

Display

boiling

points

CLS DIM substance$(1 TO 8) DIM boilingPoint(1 TO 8) CALL Display(substance$(), boilingPoint()) REM --- Data: substance, boiling point DATA Copper, 1187, Ethyl Alcohol, 78, Gold, DATA

Lead,

DATA

Silver,

1756,

Mercury,

2193,

Water,

356,

Oxygen,

2660

-182.97

100

END

SUB Display (substance$(), boilingPoint()) REM Read substances and boiling points. FOR

index

=

1 TO

8

READ substance$(index), boilingPoint (index) IF boilingPoint(index) > 100 THEN PRINT substance$(index), boilingPoint (index) END

NEXT END

SUB

IF

index

304

Arrays

Table 7.10

Substance

Boiling point (°C)

Substance

Boiling point (°C)

Copper Ethyl alcohol Gold Lead

1187 78 2660 1756

Mercury Oxygen Silver Water

35 -183 2193 100

Boiling Points

46. Write a program that inputs names and associated telephone numbers from the user and inserts them into parallel arrays. The insertion should maintain the arrays in ascending order by name. In cases where two or more names are identical, the telephone numbers for the names should be in ascending order. Hint: Treat the telephone numbers as strings. 47. Modify the program in Exercise 46 so that names can be deleted from the list. In cases where there are two or more matches, request a telephone number to uniquely identify the name to delete. Do not assume the user will input valid names or numbers. 48. Given the elements in Table 7.11, write a program to load the information into four arrays of range 1 to 6, element$(), symbol$(), atomicNum(), and massNum(), and ask the user for an element. Have the computer find the element and display its symbol, atomic number, and mass number. Account

for the case in which the user requests an element that is not in the table.

Table 7.11

Element

Symbol

Atomic #

Mass #

Hydrogen Helium

H He

i 2

1 +

Lithium

Li

3

7

Carbon Sodium Oxygen

(e Na O

6 el 8

IZ 23 16

Atomic Data

49. Suppose letter grades are assigned as follows: 97 and above 94-96 90-93 87-89 84-86 80-83 77-79

Write letter. always

A+ ji) AB+ B BC+

74-76 70-73 67-69 64-66 60-63 0-59

C CD+ D DF

a program that accepts a grade as input and displays the corresponding (Hint: This problem shows that when you search an array, you don’t look for equality. Set up an array range() containing the values 97,

94, 90, 87, 84,..., 59 and the parallel array letter$() containing A, A-, B+, ...,F Next, perform a sequential search to find the first i such that range(i) is less than or equal to the input grade.)

7.3.

ING G RCH N SEA AND I SORT

= 305

SOLUTIONS TO PRACTICE PROBLEMS 7.2 1. Yes, provided each element of the array has the same value.

2. The third CASE tests for duplicates and only assigns one array element to the third matrix if duplicates are found in the two arrays. Thus, we remove the third CASE and change the first CASE so it will process any duplicates. A situation where you would want to merge two lists

while retaining duplications is the task of merging two ordered arrays of test scores. SELECT

CASE

first$(m)

CASE IS second$(n)

LET

third$(r)

LET

n=n+1

= second$(n)

SELECT

SORTING AND SEARCHING A sort is an algorithm for ordering an array. Of the many different techniques for sorting an array, we discuss two, the bubble sort and the Shell sort. Both sorts use the QBasic statement SWAP. If varl and var2 are variables of the same type (that is, both numeric or both string), then the statement SWAP

varl,

var2

assigns varl’s value to var2, and var2’s value to varl.

EXAMPLE SOLUTION

1

Write a program to alphabetize two words supplied by INPUT statements. REM Alphabetize two words CLS INPUT "First word"; first$ INPUT "Second word"; second$ IF first$ > second$ THEN SWAP first$, second$ END

IF

PRINT

first$;

" before

";

second$

END

[run] First

word?

Second age

beauty

word?

before

age beauty

Bubble Sort The bubble sort is an algorithm that compares adjacent items and swaps those that are out of order. If this process is repeated enough times, the list will be

306

Arrays

ordered. Let’s carry out this process on the list Pebbles, Barney, Wilma, Fred,

Dino. The steps for each pass through the list are as follows: 1. Compare the first and second items. If they are out of order, swap them. 2. Compare the second and third items. If they are out of order, swap them.

3. Repeat this pattern for all remaining pairs. The final comparison possible swap is between the second-to-last and last elements.

and

The first time through the list, this process is repeated to the end of the list. This is called the first pass. After the first pass, the last item (Wilma) will be in

its proper position. Therefore, the second pass does not have to consider it and so requires one less comparison. At the end of the second pass, the last two items will be in their proper position. (The items that must have reached their proper position have been underlined.) Each successive pass requires one less comparison. After four passes, the last four items will be in their proper positions and, hence, the first will be also. Pebbles . _ Barney

Barney

Barney

Barney

First

Barney

Pebbles —»Pebbles

| Pebbles

— Pebbles

Pass

Wilma

Wilma —»> Wilma

Fred

Fred

Fred

Fred

Fred

epee

Dino

Dino

Dino

Dino

Dino

Wilma

Barney —» Barney

Barney

Barney

Second

Pebbles —» Pebbles

Fred

Fred

Pass

Fred

foe

Pebb les

Dino

Dino

Dino

be

Wilma

Wilma

Wilma

Barney —» Barney

Barney

Third

Fred ——+ Fred

Dino

Pass

Dino

Dino

Fred

Pebbles

Pebbles

Musee

Wilma

Wilma

Wilma

ow Pebbles Wilma

Barney —> Barney Fourth

Dino ——» Dino Pebbles

Pebbles

Wilma

Wilma

EXAMPLE 2

Write a program to alphabetize the names Pebbles, Barney, Wilma, Fred, Dino.

SOLUTION _

Sorting the list requires a pair of nested loops. The inner loop performs a single pass and the outer loop controls the number of passes.

7.3.

REM

Alphabetize

a list

CLS DIM name$(1 TO REM Read names FOR i = 170 5 READ name$(i) NEXT i REM Bubble sort FOR passNum = 1 FOR i = 1 TO

of

five

307

names

5)

names TO 4 ‘Number 5 - passNum

IF name$(i) > name$(i + 1) SWAP name$(i), name$(i END

SORTING AND SEARCHING

of

passes is 1 less than number of items ‘Each pass needs 1 less comparison

THEN + 1)

IF

NEXT

NEXT

REM

passNum

Display

alphabetized

list

FAR 7 2 il yO s PRINT name$(i), NEXT 7 REM

---

DATA

Data:

Pebbles,

name

Barney,

Wilma,

Fred,

Dino

END [run] Barney

EXAMPLE 3.

Dino

Fred

Pebbles

Wilma

Table 7.12 contains facts about the ten most populous metropolitan areas with listings in ascending order by city name. Sort the table in descending order by population.

Metro Area

Population in Millions

Median Income % Native | per Household __ to State

% Advanced Degree

Boston Chicago Dallas Detroit

4.2 8.1 3.9 4.7

$40,666 $35,918 $32,825 $34,729

73 is 64 76

12 8 8 i

Houston

3G

$31,488

67

8

Los Angeles

14.5

$36,711

59

8

New York Philadelphia San Francisco Washington

18.1 5.9 6.3 3.9

$38,445 $35,797 $41,459 $47,254

73 70 60 a)

it 8 11 17

Note: Column 4 gives the percentage of residents who were born in their current state of residence. Column 5 gives the percentage of residents age 25 or older with a graduate or professional degree.

Table 7.12

The Ten Most Populous Metropolitan Areas

Source: The 1990 Census

308

Arrays

SOLUTION

After the data are written into parallel arrays, the collection of parallel arrays is sorted based on the array pop(). Each time two items are SWAPed in the array pop(), the corresponding items are SWAPed

in each of the other arrays. This

way, for each city, the items of information remain linked by REM

Sort

table

of metropolitan

areas

by

population

CLS DIM city$(1 TO 10), pop(1 TO 10), income(1 TO 10) DIM natives(1 TO 10), advDeg(1 TO 10) CALL ReadData(city$(), pop(), income(), natives(), CALL SortData(city$(), pop(), income(), natives(), CALL ShowData(city$(), pop(), income(), natives(), REM

---

Data:

city,

pop.,

med.

income,

DATA

Boston,

DATA

Chicago,

DATA

Dallas,

DATA

Detroit,

4.7,

34729,

76,

7

DATA

Houston,

3.7,

31488,

67,

8

DATA

Los

Angeles,

DATA

New

York,

DATA

Philadelphia,

DATA

San

DATA

Washington,

4.2,

40666,

8.1,

73,

35918,

3.9,

14.5,

18.1,

64,

5.9,

Francisco,

8

59,

73,

35797,

6.3,

3.9,

8

36711,

38445,

8

11

70,

41459,

47254,

% native,

advDeg()) advDeg()) advDeg()) % advanced degree

12

73,

32825,

acommon subscript.

32,

8

60,

11

17

END

SUB ReadData (city$(), REM Read city, pop., FOR

i

=

READ

10

city$(i),

pop(i),

income(i),

natives(i),

advDeg(i)

7

NEXT END

1 TO

pop(), income(), natives(), advDeg()) med. income, % native, % advanced degree

SUB

SUB ShowData (city$(), pop(), income(), natives(), advDeg()) REM Display ordered table PRINT , "Pop. in", "Med. income", "% Native", "% Advanced" PRINT “Metro Area", "millions", "per hsd", "to State", "Degree" PRINT FOR i = 1 TO 10 PRINT city$(i), pop(i), income(i), natives(i), advDeg(i) NEXT END SUB

SUB SortData (city$(), pop(), income(), natives(), advDeg()) REM Bubble sort table in descending order by population FOR passNum = 1 TO 9 FOR index = 1 TO 10 - passNum IF pop(index) < pop(index + 1) THEN CALL SwapData(city$(),pop(),income() ,natives() ,advDeg() , index) END

NEXT

IF

index

NEXT passNum END SUB

ING G SEARCH ANDIN 7.3. SORT

SUB SwapData REM

Swap

SWAP SWAP SWAP SWAP SWAP END SUB

(city$(),

pop(),

income(),

natives(),

advDeg(),

309

index)

entries

city$(index), city$(index + 1) pop(index), pop(index + 1) income(index), income(index + 1) natives(index), natives(index + 1) advDeg(index), advDeg(index + 1)

[run] Metro

Area

New York Los Angeles Chicago San Francisco Philadelphia Detroit Boston Dallas Washington Houston

Pop. in millions

18.1 14.5 8.1 6.3 5.9 4.7 4.2 oN) 329 Bail

Med. income per hsd

38445 36711 35918 41459 35797 34729 40666 32825 47254 31488

% Native to State

73 59 73 60 70 76 73 64 32 67

% Advanced Degree

ila 8 8 11 8 i 12 8 17 8

Shell Sort The bubble sort is easy to understand and program. However, it is too slow for really long lists. The Shell sort, named for its inventor, Donald L. Shell, is much more efficient in such cases. It compares distant items first and works its way down to nearby items. The interval separating the compared items is called the gap. The gap begins at one-half the length of the list and is successively halved until eventually each item is compared with its neighbor as in the bubble sort. The algorithm for a list of n items is as follows.

1. Begin with a gap of g = INT(n/ 2). 2. Compare items | and 1 + g, 2 and2 + g,...,n—gandn. Swap any pairs that are out of order.

3. Repeat step 2 until no swaps are made for gap g.

4. Halve the value of g. 5. Repeat steps 2, 3, and 4 until the value of g is 0. The Shell sort is illustrated below. Crossing arrows indicate that a swap occurred. Initial Gap = INT([Number of Items] / 2) = INT(5 / 2) = 2

310

Arrays

Pebbles

Pebbles

Barney —> Barney

Barney

Pebbles —» Pebbles First

Barney

Pass

Wilma

—> Wilma

Wilma

Dino

Fred

Fred ——»

Fred ve

Fred

Dino

Dino

Dino

Wilma

Since there was a swap, use the same gap for the second pass. Dino

Dino

Pebbles

Dino

Second

Bamey X

Barney —> Barney

Pass

Dino

Pebbles

Fred

Fred ——»

Fred

Wilma

Wilma

Wilma—» Wilma

Barney

§ Pebbles—» Pebbles Fred

Again, there was a swap, so keep the current gap. Dino

Dino

Dine 2.

Dino

Third

Barney

Barney —> Barney

Pass

Pebbles—» Pebbles

Barney

| Pebbles —» Pebbles

Fred

Fred ——»

Fred

Wilma

Wilma

Wilma

Fred —»> Wilma

There were no swaps for the current gap of 2 so, Next Gap = INT([Previous Gap] / 2) = INT(2 / 2) = 1 Dino

Barney

Barney

Fourth

Barney

Dino ——» Dino

Pass

Pebbles

= Pebbles—» ae

Barney

Barney

Dino

Dino

Fred

Fred

Fred

Fred

Fred

Pebbles —» Pebbles

Wilma

Wilma

Wilma

Wilma —» Wilma

Since there was a swap (actually two swaps), keep the same gap. Barney _» Barney

Barney

Barney

Barney

Fifth

Dino ——~ Dino ——»

Dino

Dino

Dino

Pass

Fred

Fred ——»

Fred ——»

Fred

Fred

Pebbles

Pebbles

Pebbles —-» Pebbles >

Wilma

Wilma

Wilma

Pebbles

Wilma—» Wilma

Since there were no swaps for the current gap, then Next Gap = INT([Previous Gap] / 2) = INT(1 /2) =0

and the Shell sort is complete.

7.3.

SORTING AND SEARCHING

311

Notice that the Shell sort required 14 comparisons to sort the list whereas the bubble sort required only 10 comparisons for the same list. This illustrates the fact that for very short lists, the bubble sort is preferable; however, for lists

of 30 items or more, the Shell sort will consistently outperform the bubble sort. Table 7.13 shows the average number of comparisons required to sort arrays of varying sizes.

Array Elements

Table 7.13

EXAMPLE

Bubble Sort Comparisons

Shell Sort Comparisons

5

10

1)

10

45

oy

15 20 25

105 190 300

| 19) 302

30 50 100 500 1000

435 1225 4950 124,750 499,500

364 926 2638 Ldvokl 58,460

Efficiency of Bubble and Shell Sorts

4 _ Use the Shell sort to alphabetize the parts of a running shoe (see Figure 7.6).

tongue eyelets

heel patch/ Achilles’ tendon pad

binding padding

eye stay

toe box

trim

ry

/

stud

f.

uppers

outsole

sole

midsole wedge

manufacturer s ornament

Figure 7.6

Running Shoe

foxiNg

heel counter

312

Arrays

SOLUTION

In the following program, the data are read into part of an array. In subprogram ReadData, the variable numParts both provides the subscripts the array and serves as a counter. The final value of numParts is passed to other subprograms. The subprogram SortData uses a flag to indicate if a swap been made during a pass. REM

Sort

and

display

parts

of

running

GES DIM part$(1 TO 50) CALL ReadData(part$(),

numParts)

CALL SortData(part$(),

numParts)

CALL ShowData(part$(),

numParts)

shoe

REM --- Data: part of running shoe DATA toe box, vamp, laces, eye stay, eyelets, tongue DATA binding, padding, heel patch, heel counter, foxing DATA midsle wdge, mfg's ornmt, sole DATA

uppers,

trim,

stud,

outsole,

EOD

END

SUB ReadData

(part$(),

numParts)

REM Read part names LET numParts = 0 READ item$ DO

WHILE

LET

item$

numParts

"Number "EOD"

= numParts

LET part$(numParts) READ item$ LOOP END SUB

SUB ShowData

(part$(),

+

1

= item$

numParts)

REM Display sorted list FOR i = 1 TO numParts PRINT part$(i), NEXT i END SUB

SUB SortData

of parts

(part$(),

of parts

numParts)

REM Shell sort shoe parts LET gap = INT(numParts / 2) DO WHILE gap >= 1 DO LET doneFlag = 1 FOR index = 1 TO numParts

- gap

IF part$(index) > part$(index + gap) THEN SWAP part$(index), part$(index + gap) LET END

doneFlag

IF

NEXT index LOOP UNTIL doneFlag

LET gap = INT(gap LOOP END

SUB

= 0

= 1

/ 2)

‘Halve

the length

of the gap

the for the has

7.3.

[run] binding

eye

heel

laces

mfg's

padding

sole

stud

trim

uppers

vamp

patch

stay

eyelets

SORTING AND SEARCHING

foxing ornmt

midsle toe

heel wdge

box

313

counter

outsole tongue

Searching Suppose we had an array of 1000 names in alphabetical order and wanted to locate a specific person in the list. One approach would be to start with the first name and consider each name until a match was found. This process is called a sequential search. We would find a person whose name begins with “A” rather quickly, but 1000 comparisons might be necessary to find a person whose name begins with “Z.” For much longer lists, searching could be a time-consuming matter. However, when the list has already been sorted into either ascending or descending order, there is a method, called a binary search, that shortens the

task considerably. Let us refer to the sought item as quarry. The binary search looks for quarry by determining in which half of the list it lies. The other half is then discarded and the retained half is temporarily regarded as the entire list. The process is repeated until the item is found. The algorithm for a binary search of an ascending list is as follows (Figure 7.7 contains the flowchart for a binary search): 1. At each stage, denote the subscript of the first item in the retained list by first and the subscript of the last item in the retained list by last. Initially, the value of first is 1 and the value of last is the number of items in the list.

2. Look at the middle item of the current list, the item having the subscript middle = INT ((first + last) / 2).

3. If the middle item is quarry, then the search is over. 4. If the middle item is greater than quarry, then quarry should be in the first half of the list. So the subscript of quarry must lie between first and middle — 1. That is, the new value of last is middle — 1.

5. If the middle item is less than quarry, then quarry should be in the second half of the list of possible items. So the subscript of quarry must lie between middle + 1 and last. That is, the new value of first is middle + 1.

6. Repeat steps 2 through 5 until quarry is found or until the halving process uses up the entire list. (When the entire list has been used up, first > last.) In the second case, quarry was not in the original list.

314

Arrays

Get quarry Set first, last Set flag = 0

Is first < last AND flag = 0 0)

Calculate middle

middle item = quarry

2

middle item > quarry

2

Set first = middle + 1

Figure 7.7

Flowchart for a Binary Search

EXAMPLE 5

Assume the array firm$() contains the alphabetized names of 100 corporations. Write a program that requests the name of a corporation as input and uses a binary search to determine whether or not the corporation is in the array.

SOLUTION —

REM array firm$()

already ordered alphabetically

CLS INPUT

"Enter

the

name

of

a corporation:

REM Binary search of firm$() LET foundFlag = 0 BET

Shiiesite

LET

last

= =

100

",

corp$

for corp$ ‘1 indicates

corp$

found

7.3.

DO WHILE (first corp$ LET last = middle - 1 CASE IS < corp$ LET first = middle + 1 SELECT

END LOOP

1 THEN

=

foundFlag

IF

" found."

PRINT corp$; BESE

PRINT END

" not found."

corp$;

IF

END

Suppose the corporation input in Example 5 is in the second half of the array. On the first pass, middle would be assigned INT((1 + 100)/2) = INT(50.5) = 50

and then first would be altered to 50 + 1 = 51. On the second pass, middle would be assigned INT((51 + 100))/2 = INT(75.5) = 75. If the corporation is not the

array element with subscript 75, then either last would be assigned 74 or first would be assigned 76 depending upon whether the corporation appears before or after the 75th element. Each pass through the loop halves the range of subscripts containing the corporation until the corporation is located. In Example 5, the binary search merely reported whether or not an array contained a certain item. After finding the item, its array subscript was not needed. However, if related data are stored in parallel arrays (as in Table 7.4),

the subscript of the found item can be used to retrieve the related information in the other arrays. This process, called a table lookup, is used in the following example.

EXAMPLE 6

Suppose the cities in Example 3 have been ordered alphabetically. Use a binary search procedure to locate the data for a city requested by an INPUT statement.

SOLUTION

In the following program, the DATA statements have been ordered by the name of the city. REM

Search

for

city

in

the

metropolitan

areas

table

GIES DIM city$(1 TO 10), pop(1 TO 10), income(1 TO 10) DIM natives(1 TO 10), advDeg(1 TO 10) CALL ReadData(city$(), pop(), income(), natives(), advDeg()) CALL GetCityName(searchCity$) CALL FindCity(city$(),pop(),income(),natives(),advDeg(),searchCity$) REM

---

Data:

city,

4.2,

pop.,

Boston,

DATA

Chicago,

DATA

Dallas,

DATA

Detroit,

4.7,

34729,

76,

7

DATA

Houston,

3.7,

31488,

67,

8

3.9,

35918,

32825,

73,

income,

DATA

8.1,

40666,

med.

12

73,

64,

8

8

% native,

% advanced

degree

316

Arrays

36711,

14.5,

Angeles,

8

59,

DATA

Los

DATA DATA DATA DATA END

New York, 18.1, 38445, 73, 11 Philadelphia, 5.9, 35797, 70, 8 San Francisco, 6.3, 41459, 60, 11 Washington, 3.9, 47254, 32, 17

,natives(),advDeg() ,searchCity$)

(city$(),pop(),income()

FindCity

SUB

Binary

LET

foundFlag

HET

qhnieSie

LET

last

city

for

table

search

REM

name

'l

= 0

= city

found

Sal

=

10

DO WHILE (first searchCity$

CASE

1

-

= middle

last

LET

CASE IS < searchCity$ LET first = middle + 1 SELECT

END

LOOP

END

file"

in

not

"City

PRINT END

= 0 THEN

foundFlag

IF

IF

SUB

SUB GetCityName (searchCity$) REM Request name of city as INPUT "City"; searchCity$ END

SUB

SUB ReadData (city$(), REM Read city, pop., FOR

1

=

READ NEXT

END

input

2 10

pop(), income(), natives(), advDeg()) med. income, % native, % advanced degree

10

city$(i),

pop(i),

income(i),

natives(i),

3

SUB

SUB ShowData REM

(city$(),

Display

PRINT

,

PRINT

"Metro

city

"Pop.

pop(),

and

in",

income(),

associated "Med.

natives(),

income",

"%

Native",

"millions",

"per

PRINT

city$(index),

pop(index),

income(index),

PRINT

natives(index),

hsd",

"to

PRINT

SUB

[run] City? Baltimore City not in file

advDeg(),

index)

information

Area",

END

advDeg(i)

advDeg(index)

"%

Advanced"

State",

"Degree"

7.3.

SORTING AND SEARCHING

317

Comments:

1. Suppose our bubble sort algorithm is applied to an ordered list. The algorithm will still make n — 1 passes through the list. The process could be

shortened for some lists by flagging the presence of out-of-order items as in the Shell sort. It may be preferable not to use a flag since for greatly disordered lists, the flag would slow down an already sluggish algorithm. - In Example 3, parallel arrays already ordered by one field were sorted by another field. Usually, parallel arrays are sorted by the field to be searched when accessing the file. This field is called the key field.

. Suppose an array of 2000 items is searched sequentially; that is, one item after another, in order to locate a specific item. The number of comparisons

would vary from 1 to 2000, with an average of 1000. With a binary search, the number of comparisons would be at most 11, since 2!! > 2000.

. The built-in function UCASE$ converts all the characters in a string to uppercase. UCASE$ is useful in sorting and searching arrays when the alphabetic case (upper or lower) is unimportant. For instance, in Example 5, if UCASE$

were included in the SELECT CASE comparisons, then the

binary search would locate “Mobil” in the array even if the user entered “MOBIL”. . The SWAP statement cannot be used to switch all the values of two arrays at once. For instance, if a() and b() are arrays, then the statement SWAP a, b or SWAP a(), b() will not do the job. Instead, a loop must be set up to

interchange each of the corresponding elements separately.

. The QBasic function TIMER can be used to determine the speed of a sort. Precede the sort with the statement LET t = TIMER.

After the sort has

executed, the statement PRINT TIMER - t will display the duration of the sort in seconds.

PRACTICE PROBLEMS

7.3

1. The pseudocode for a bubble sort of an array of n items is given below. Why is the terminating value of the outer loop n — 1 and the terminating value of the inner loop n — j? FORA = 1O n= 1 FOR k= 1 TOn=j IF [kth and (k+1)st items are out of order] THEN SWAP them NEXT k NEXT j

2. Complete the table by filling in the values of each variable after successive passes of a binary search of a list of 20 items, where the sought item is in the 13th position. First

1 11

Last

20 20

Middle

10

318

Arrays

7.3

EXERCISES

m. gra pro the of put out the ine erm det 4, h oug thr 1 ses rci Exe In 2. DIM gag$(1

1. LET p = 100

TO 2)

LET q = 200 SWAP p, q PRINT p; q

READ gag$(1), gag$(2) IF gag$(2) < gag$(1) THEN SWAP gag$(2), gag$(1)

END

END

IF

PRINT gag$(1),

gag$(2)

REM --- Data: comedians DATA Stan, Oliver END

4. DIM a(1 TO 3)

3. INPUT x, y

SWAP x, Y LET swappedFlag

= 1

IF swappedFlag = 1 THEN PRINT "Numbers interchanged."

> a(k

a(k)

a(k),

SWAP IF

END

1)

THEN

a(k

+ 1)

+

k

NEXT

IF

1043-93

ke=" IF

8X32 is

eO0mZ

aa

FOR

PRINT

END

j

NEXT FOR

IF

END

a(j)

READ

y > x THEN

IF

aaaleOns

FORSd

= 0

swappedFlag

LET

j

END

NEXT

and 11 as input.) 7 s (Use the number

sikh NEXT

j

REM

---

an numbers

Data:

DAWAt/

seo

4

END

In Exercises 5 and 6, identify the errors. 6. DIM a(1 TO 3), b(1 TO 3)

5. DIM c(1 TO 4), d$(1 TO 4) FOR

EORSim

4

NEXT

7

DYN

Data:

---

Wh, 25

da

REM

numbers

Hy

leaOes b(i)

a(i), 7

SWAP a(i), b(i)

SWAP c(4), d$(4) REM

=e

READ

d$(i)

c(i),

READ NEXT

1 10

i =

Gy

75

Gy

---

DATARS

&

numbers

Data:

SSee 575095,

Ul

END

END

7. Which type of search would be best for the array shown below? 1

2

3

4

5

SORTING AND SEARCHING

7.3.

319

8. Which type of search would be best for the array shown below? 1

d,

a

4

5

- Consider the items Tin Man, Dorothy, Scarecrow, and Lion, in that order.

After how many swaps in a bubble sort will the list be in alphabetical order? - How many comparisons will be made in a bubble sort of 6 items? - How many comparisons will be made in a bubble sort of n items? - Modify the program in Example 2 so that it will keep track of the number of swaps and comparisons and display these numbers before ending.

- Rework Exercise 9 using the Shell sort.

. How many comparisons would be made in a Shell sort of 6 items if the items were originally in descending order and were sorted in ascending order? 15. If a list of 6 items is already in the proper order, how many comparisons will be made by a Shell sort? 16. The following subprogram fills an array of 200 integers with values between

0 and 63 that are badly in need of sorting. Write a program that uses the subprogram and sorts the array nums() with a bubble sort. Run the program and time the execution. Do the same for the Shell sort. SUB

FillArray

REM

Generate

(nums()) numbers

from

LET nums(1) = 5 FOR i = 2 TO 200 LET nums(i) = (9 * nums(i NEXT i END SUB

0 to

63

- 1)

and

+ 7)

place

MOD

in

array

64

liz: Suppose a list of 5000 numbers is to be sorted, but the numbers consist of only 1, 2, 3, and 4. Describe a method of sorting the list that would be much faster than either the bubble or Shell sort. 1S: The bubble sort gets its name from the fact that in an ascending sort successive passes cause “lighter” items to rise to the top like bubbles in water. How did the Shell sort § get its name? 19. What is the maximum number of comparisons required to find an item in a

sequential search of 16 items? What is the average number of comparisons? What is the maximum number of comparisons required to find an item in a binary search of 16 items?

20. Redo Exercise 19 with 2N items, where N is any positive integer.

320

Arrays

d. tan ers und to y eas is and a dat of s set ll sma on ent ici eff is t sor 21. The insertion g yin pla of d han a er ord ple peo t mos t tha er nn ma e sam the It is carried out in cards:

(1) Read the first item of data and place it in an array. tive rela ced pla be uld sho it re whe ide dec and data of m ite t nex the d Rea (2)

a dat ng sti exi e mov , ary ess nec If y. arra the in red sto y ead alr a dat to the in m ite new the Put m. ite new the for ce spa e mak to ay arr the in down its appropriate location. the in er ord in ced pla and d rea n bee has a dat all il unt 2 p ste eat Rep (3) array.

Suppose up to 100 items are stored in DATA statements. Use the insertion sort to place the items into an ascending ordered array.

JV An ascending selection sort of an array is carried out with the following steps:

(1) Search the array for the element with the smallest value and exchange it with the first element. (2) Search the remaining second through last elements for the smallest value and exchange it with the second element. (3) Continue this process for each element of the array in succession. Write a procedure to accept an array as input and order it with a selection sort. In Exercises 23 through 30, write a short program (or partial program) to complete the stated task. 23. Without using the SWAP ables x and y.

statement, interchange the values of the vari-

24. Display the names of the seven dwarfs in alphabetical order. As the DATA statement use: DATA

Doc,

Grumpy,

Sleepy,

Happy,

Bashful,

Sneezy,

Dopey

25. Table 7.14 lists the top 10 most attended exhibits in the history of the National Gallery of Art. Read the data into a pair of parallel arrays and display a similar table with the exhibit names in alphabetical order. 26. Table 7.15 contains data for the nine planets of our solar system (rounded to whole numbers). Write a program to read the data into parallel arrays, and then output a list of the planets sorted according to size, period of rotation, or period of revolution, as specified by the user. Note: The periods given in terms of days must be converted to hours or years.

27. The median of a set of n measurements is a number such that half the n measurements fall below the median and half fall above. If the number of measurements n is odd, the median is the middle number when the meas-

urements are arranged in ascending or descending order. measurements n is even, the median is the average of measurements when the measurements are arranged in scending order. Write a program that requests a number measurements as input and then displays the median.

If the number of the two middle ascending or den and a set of n

7.3.

SORTING AND SEARCHING

Attendance (in thousands)

Exhibit

1053 999 836

Rodin Rediscovered Treasure Houses of Britain Treasures of Tutankhamen

Table 7.14

Chinese Archaeology

684

Ansel Adams Splendor of Dresden Wyeth’s Helga Pictures Post-Impressionism Matisse in Nice John Hay Whitney Collection

652 617 558 558 537 513

National Gallery of Art’s Greatest Hits

Planet

Diameter (km)

Period of Rotation

Period of Revolution

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

4,880 125122 12,742 6,800 143,000 121,000 52,000 50,000 2,290

59 43 24 24 10 10 17 16 6

88 225 365 687 12 30 84 165 248

Table 7.15

321

days days hours hours hours hours hours hours days

days days days days years years years years years

Planet Data

28. An airline has a list of 200 flight numbers in an ascending sorted array. Accept a number as input and do a binary search of the list to determine if the flight number is valid. 29. Modify the program in Exercise 16 to compute and display the number of times each of the numbers from 0 through 63 appears. 30. Allow a number n to be input by the user. Then accept as input a list of n numbers. Place the numbers into an array and apply a bubble sort. 31. Write a program that accepts an American word as input and performs a binary search to translate it into its British equivalent. Use the following list of words for data and account for the case when the word requested is not in the list. American

British

American

British

attic business suit elevator flashlight french fries gasoline

loft lounge suit lift torch chips petrol

ice cream megaphone radio sneakers truck zeTO

ice loud hailer wireless plimsolls lorry nought

322,

“Artays

The s. mal ani in nd fou ts men ele al mic che mon com the ws sho 7.16 32. Table te Wri . ght wei y bod an hum of t cen per of er ord g sin rea dec in m the table lists a menu-driven program to display the table in: (a) the order given

(b) increasing order according to atomic weight (c) increasing order according to atomic number Use calls to a single Shell Sort subprogram to accomplish tasks (b) and (c) above.

Symbol

Element

Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus Chlorine Sulfur Potassium Sodium Magnesium lodine Iron Table 7.16

Approximate Atomic Weight

O O Et N Ca le Cl S K

16 12 It 14 40 31 oe: 32 39

Na Mg

MS 24

I Fe

Ley 56

Atomic Number

Chemical Elements Found in Animals

33. Write a program that accepts a student’s name and seven test scores as input and calculates the average score after dropping the two lowest grades. 34. Table 7.17 shows the boiling points of selected metals. Write a program to READ the information into parallel arrays and display it in increasing order of boiling point temperature.

Metal

Aluminum Barium Calcium Cesium Lithium

Table 7.17

Boiling Point (°C) 2330 1640 1487 690 1367

Boiling Metal Manganese Potassium Rubidium Sodium Strontium

Point (°C)

1126 119 679 892 1384

Boiling Points of Metals

35. Given the flight schedule in Table 7.18, write a program to load the information into four arrays of range | to 5, flightNum(), orig$(), dest$(), and deptTime$(), and ask the user to request a flight number. Have the computer find the flight number using a binary search and display the information corresponding to that flight. Account for the case where the user requests a nonexistent flight.

TWO-DIMENSIONAL ARRAYS

7.4

Table 7.18

Flight #

Origin

Destination

Departure Time

iby 209) 298 326 445

Tucson LEN Albany Houston New York

Dallas Boston Reno New York Tampa

8:45 10:15 1:35 2:40 4:20

323

a.m. a.m. p.m: p.m. p.m.

Flight Schedule

SOLUTIONS TO PRACTICE PROBLEMS 7.3 1. The outer loop controls the number of passes, one less than the number of items in the list. The inner loop performs a single pass, and the jth pass consists of n — j comparisons. 2.

First

Last

Middle

l

20 20 14 14

10 15 Le 13

Il 11 1S

7 ;4

TWO-DIMENSIONAL

ARRAYS

Each array discussed so far held a single list of items. Such called single-subscripted variables. An array can also hold table with several rows and columns. Such arrays are called arrays or double-subscripted variables. Two tables are shown gives the road mileage between certain cities. It has four rows Table 7.20 shows the leading universities in three disciplines. and five columns.

Chicago Los Angeles New York Philadelphia

array variables are the contents of a two-dimensional below. Table 7.19 and four columns. It has three rows

Chicago

Los Angeles

New York

Philadelphia

0 2054 802 738

2054 0 2786 2706

802 2786 0 100

738 2706 100 0

Table 7.19 Road Mileage Between Selected U.S. Cities

1

2

3

4

5

Business

UofPA

MIT

U of IN

U of MI

UC Berk

Comp Sc.

MIT

Cng-Mellon

UC Berk

Cornell

U of IL

Engr/Gen.

UCLA

U of IL

Uof MD

U of OK

Stevens I.T.

Table 7.20

University Rankings

Source: A Rating of Undergraduate Programs in American and International Universities, Dr. Jack Gourman, 1993

324

Arrays

Two-dimensional array variables store the contents of tables. They have the same types of names as other array variables. The only difference is that they have two subscripts, each with its own range. The range of the first subscript is determined by the number of rows in the table and the range of the second subscript is determined by the number of columns. The statement DIM arrayName(m1

TO nl,

first be

m2

if

TO x

Kor

last row

last column

first column

dimensions an array corresponding to a table with rows labeled from m1 TO nl] and columns labeled from m2 TO n2. The entry in the jth row, kth column is arrayName(j,k). For instance, the data in Table 7.19 can be stored in an array named rm(). The statement DIM

rm(1

TO 4,

1 TO 4)

will dimension the array. Each element of the array has the form rm(row, column). The entries of the array are rm(1,1)=0 toa(241 )=2054 rm(3,1)=802

rm(1,2)=2054 Tim ee) =O rmi(3,2)=2786

rm(4,1)=738

rm(4,2)=2706

= rm(1,3)=802 mi(2,3)=2786 m(3,3)=0

rm(4,3)=100

rm(1,4)=738 m(2,4)=2706 rm(3,4)=100

rm(4,4)=0

The data in Table 7.20 can be stored in a two-dimensional string array named univ$(). The statement DIM

univ$(1

TO 3,

1 TO 5)

will dimension the array. Some of the entries of the array are univ$(1,1) ="U of PA" unive(7.3) ="UG Berk" univ$(3,5) = "Stevens I.T."

EXAMPLE SOLUTION

1

Write a program to store and access the data from Table 7.19. Data are read into a two-dimensional array using a pair of nested loops. The outer loop controls the rows and the inner loop controls the columns. REM

Determine

road

mileage

between

OES DIM

rm(1

TO

4,

1 TO

4)

CALL

ReadMileages(rm())

CALL

ShowCities

CALL InputCities(row, col) CALL ShowMileage(rm(), row, REM --- Data: distances DATA 0, 2054, 802, 738 DATA 2054, 0, 2786, 2706

col)

cities

TWO-DIMENSIONAL ARRAYS

7.4.

DATA 802, DATA 738, END

2786, 2706,

0, 100 100, 0

SUB InputCities (row, col) REM Input origin and destination INPUT "Origin"; row INPUT "Destination"; col END SUB

SUB ReadMileages (rm()) REM Read mileages into FOR row = 1 TO 4 FOR col = 1 TO 4 READ rm(row, col) NEXT col NEXT

END

325

cities

a two-dimensional

array

row

SUB

SUB ShowCities REM Show possible cities PRINT "1. Chicago" PRINT "2. Los Angeles" PRINT "3. New York" PRINT "4. Philadelphia" PRINT END SUB

SUB ShowMileage (rm(), row, col) REM Display mileage between cities PRINT "The road mileage is"; rm(row, END

SUB

1.

Chicago

2.

Los

Angeles

3.

New

York

4.

Philadelphia

Origin? 3 Destination? The

col)

road

1

mileage

is 802

So far, two-dimensional arrays have only been used to store data for convenient lookup. In the next example, an array is used to make a valuable computation. EXAMPLE

2.

The Center for Science in the Public Interest publishes The Nutrition Scorebook, a highly respected rating of foods. The top two foods in each of five categories

are shown in Table 7.21 along with some information on their composition. Write a program to compute the nutritional content of a meal. The table should be read into an array and then the program should request the quantities of each food item that is part of the meal. The program should then compute the amounts of each nutritional component consumed by summing each column with each entry weighted by the quantity of the food item.

326

Arrays

Calories

Protein (grams)

23 160 230 85 65 178 110 156 5D 405

3 2 10 8 3 3.8 Z 24 126.8 28.8

spinach(1 cup) sweet potato (1 med.) yogurt(8 oz.) skim milk (1 cup) wh. wheat bread (1 slice) brown rice (1 cup) watermelon (1 wedge)

papaya (1 lg. tuna in water (1 |b.) lobster (1 med.)

Table 7.21

SOLUTION

REM

Fat (grams)

0.3 1 3

the

nutritional

content

of

73 190

table

DIM quantity(1 TO 10) CALL ReadData(comp()) CALL InputAmounts (quantity ()) CALL ShowData(comp(), quantity()) REM

---

Data:

component

data

DMV 235 35 sole SHI Ss) DATA 160, 2, 1, 9230, 46 DATA230," 10,3, 120), 343 DATA 85, 8, 0, 500, 302 DATA 65, 3, 1, 0, 24 DYNAN AUS} Slaten aSl5 Wy IKs! DATA ITO Zou lee Zool 30 DATA 156, 2.4, .4, 7000, 80 DAY SMa IOs, SeO Oy 7/5) DATA 405, 28.8, 26.6, 984, 190 REM --- Data: top-rated foods

DATA DATA DATA

spinach (1 cup), sweet potato (1 med), yogurt (8 oz) skim milk (1 cup), wh. wheat bread (1 slice) brown rice (1 cup), watermelon (1 wedge), papaya (1 1g)

DATA tuna in water (1 1b), lobster (1 med) REM --- Data: component names DATA calories, protein (grams), fat (grams) DATA vitamin A (IU), calcium (mg) END

SUB

InputAmounts

REM

Request

OR

tS

READ

END

quantities

Ih NO) food$;

TNRUT

Sees

SUB

7

of

We

food$

PRINT NEXT

(quantity())

Guan tya(in)

foods

consumed

46 343

18 30 80

a meal

‘Composition

93

24

GES

DIM comp(1 TO 10, 1 TO 5)

(mg)

302

Composition of Ten Top-Rated Foods

Determine

Calcium

7.4

SUB

ReadData

REM

Record

FOR

row

=

FORScol

END

327

(comp()) composition

1 10 =

of

foods

in

array

10

17 10%5

READ comp(row, NEXT col NEXT

TWO-DIMENSIONAL ARRAYS

col)

row

SUB

SUB ShowData (comp(), quantity()) REM Display amount of each component PRINT PRINT "This meal contains the following PRINT "of these nutritional components: FOR col = 1 710 5 LET amount = 0 READ compName$ FOR row = 1 TO 10 LET amount = amount + quantity(row) NEXT

"

* comp(row,

col)

row

PRINT compName$ NEXT col END SUB

+ ":

"3; amount

[run] spinach (1 cup): 1 sweet potato (1 med): 1 yogurt (8 oz): 1 skim milk (1 cup): 2 wh. wheat bread (1 slice): brown rice (1 cup): 0 watermelon (1 wedge): 1 papaya (1 1g): 0 tuna in water (1 1b): .5 lobster (1 med): 0

3

This meal contains the following of these nutritional components: callonies: ~11/5.5

protein

quantities"

(grams):

quantities

105.4

fat (grams): 10.1 vitamin A (IU): 20960 1224.5 calcium (mg):

Vectors and Matrices

Vectors and matrices are represented as one- and two-dimensional respectively. The statements DIM DIM

vec(1 mat(1

TO n) TO m,

1 TO

arrays,

n)

declare a vector having n entries and an m X n matrix, that is, a matrix of m rows and n columns.

328

Arrays

Programs involving matrices commonly use procedures to carry out matrix

operations. The UBOUND function can be used to obtain the size of a matrix. The values of UROUND(mat,

1) and UBOUND(mat, 2) are the number of rows

and columns of the matrix, respectively.

EXAMPLE 3

The following program multiplies a column vector on the left by a 3 x 5 matrix and displays the entries of the product. The sizes of the vector and the product are determined by the UBOUND function from the dimensions of the matrix. The program can be modified for a matrix of a different size by changing just the third line and the DATA statements. REM

Multiply

a vector

by

a matrix

CLS DIMEMatrix(Cis i0es.m

1s 1015)

DIM vector(1 TO UBOUND(matrix, 2)) DIM product(1 TO UBOUND(matrix, 1)) CALL FillEntries(matrix(), vector()) CALL Multiply(matrix(), vector(), product()) CALL ShowEntries (product ()) REM

---

Data:

DATAR/

e255

matrix

Oncc

DATARSRcas

DATA REM

6,

seca

8,

4,

1,

6

---

Data:

vector

7,

235.

2,

DATA,

9

END

SUB FillEntries (matrix(), vector()) FOR row = 1 TO UBOUND(matrix, 1) FOR

col

READ

=

1 TO

UBOUND(matrix,

matrix(row,

col)

col

NEXT

row

NEXT

FOR row = 1 TO UBOUND(matrix, READ vector(row)

2)

row

NEXT END

2)

SUB

SUB Multiply (matrix(), vector(), product()) FOR row = 1 TO UBOUND(matrix, 1) LET product(row) = 0 FOR

col

LET NEXT NEXT END

=

1 TO

UBOUND(matrix,

product(row)

= product(row)

col row

SUB

SUB ShowEntries (product ()) FOR row = 1 TO UBOUND(product) PRINT product (row) NEXT END

SUB

row

2)

+ matrix(row,

col)

* vector(col)

7.4.

ARRAYS

TWO-DIMENSIONAL

= 329

[run] 154 141 134

Comments:

1. A two-dimensional array variable can hold either numeric data or string data, but not both. 2. Three- (or higher) dimensional arrays can also be defined in a similar way

as two-dimensional arrays. For instance, a three-dimensional array uses 3 subscripts, and the assignment of values requires a triple-nested loop. As an example,

a weatherman

might

use a three-dimensional

array to record

temperatures for various dates, times, and elevations.

PRACTICE PROBLEMS

7.4

1. Consider the road mileage program in Example 1. How can the program be modified so the actual names of the cities can be supplied by the user? 2. In what types of problems are two-dimensional arrays superior to parallel arrays?

EXERCISES 7.4 In Exercises 1 through 10, determine the output of the program. Ls DIM LET

a(1 70 20; 1 10 30) fa(3..5)) =6 22 ea(3 5.5)

2. Heat capacity of a material is defined as the ratio of the heat Q supplied to the corresponding temperature rise: Heat Capacity = Q/(T7-T}) DIM

heatCapacity(1

TO

100,

1 TO

50)

BETSOF="50

LET LET

PRINT

tempRise = 20 heatCapacity(Q,

tempRise) heatCapacity(50, 20)

= 2.5

END

3. DIM year(1

TO 100,

1 TO 50)

WEI ye 7 UE Y = 8 LET year(x, y) = 1937 PRINT year(7, 8) + 50 END

4. DIM metal$(1

TO 5, 1 TO 5)

LET b$ = "Aluminum" LET metal$(2, 3) = b$ PRINT metal$(2, 3) END

330.

Arrays

«DIM actors(1 10s5.) 10=5) LET b$ = "Bogart" SWAP actor$(2, 3), b$ PRINT actor$(2, 3) PRINT actor$(3, 2) END

gq

p,

6. READ

NEXT k PRINT NEXT j REM --- Data: DATARZ aoe END DIM a(1 TO 4, 1 TO FOR j = 1 T0 4 FORKS = SI TORS

q)

DIM a{1 TO p, P10 FOR j = 1 TO p FOR) k=) 10ng READ a(j, k) PRINT a(j, k)s;

numbers

tae

mc

sO

Om

5)

. The magnetic energy stored in an inductor is e = Li’/2. L is the inductance and i is the electric current in the inductor. DIM e(1 TO 4, 1 TO FOR i = 1 T0 4 FORRES sleiOn5

Petve (sue PRINT NEXT L PRINT NEXT 7

OR

ay Sil

5)

sul

e(i,

nies i202

L),

10. READ x, y DIM power(1

1@) 3

FOR k = 1 T0 3 READ s(j, k) NEXT k NEXT

ARNT NEXT

j

REM

---

hs

ale 10x k= 1 toy

NEXT aye

- j

- k;

k

PRINT

Data:

numbers

a5

le

Se

1 TO y)

READ power(j, k) PRINT power(j, k)

Ons SiGis

go=

FOR

j

FORM i=l

DEAN END

FOR

TO x,

Ses

bia ae

NEXT

j

REM

---

Data:

xX,

y,

power

DWN

Zeiss

Assan

Say

iyi

DATA

43.2,

48.0,

51.8,

60.0

END

TWO-DIMENSIONAL ARRAYS

7.4.

331

In Exercises 11 and 12, identify the errors. 11. REM Fill Di)

ah

FORSe

an array 10

=

35

th ye) a)

1 10,4

AO

Ie = ih yO s READ a(j, k) NEXT k NEXT 3 REM

DMN

---

th,

Data:

numbers

25

Gs,

34

"S6

@,

da,

Os

@,

i,

2

END

12. REM REM

The of

voltage time

across

during

3 capacitors

---

Data:

recorded

as

a function

charging

DIM voltage(1 TO 3, 1 TO 3) AO aj 2 i TOs READ capacitorNumber FOR = TWO & READ voltage(k, j) NEXT k NEXT j INPUT "Capacitor number (1, 2 or 3)"; INPUT "Time (1, 2 or 3)"; time PRINT voltage(capacitorNumber, time) REM

is

capacitor

number,

capacitorNumber

voltages

at

3 different

times

ONDA iL, si, 2, 28 DAMN 25 Soba Boeig 59) DAW Ag Sue lis Sitio uae 5 END

In Exercises 13 through 23, write a procedure or program segment to perform the stated task. 13. Given an array dimensioned with the statement DIM a(1 TO 10, 1 TO 10),

set the entries in the jth column to j (forj = 1,..., 10).

14. Consider a system of ten bodies where each body is acted on by ten forces in the same direction. The values of the forces acting on the n‘® body are the entries of the n' row of the array force(1 TO

10, 1 TO

10). Compute

the sum of the forces acting on the 10" body. 15. Given an array dimensioned with the statement DIM a(1 TO 10, 1 TO 10), and values assigned to each entry, interchange the values in the second and third rows.

16. The period of a pendulum of length L is given by

T (seconds) = 2nVL/g where g = 9.8 m/s? is the acceleration of gravity. The values of T are measured for different values of L and stored in the array period(1 TO 3, 1 TO 4). Find the greatest value and the location(s) at which it occurs.

332

~=Arrays

45), TO 1 3, TO a(1 DIM ent tem sta the h wit ed ion ens dim y arra an en 17. Giv

and values assigned to each entry, find the greatest value and the locations (possibly more than one) at which it occurs.

18. Assume the matrices matA(), matB(), and matC() have been dimensioned with the statements DIM matA(1 TO m, 1 TO n), DIM matB(1 TO n, | TO r), and DIM matC(1 TO m, 1 TO r). Assign to matC() the product of matA() and matB().

19. Display the entries of matA(). Note: Use PRINT USING and assume the numbers of rows and columns are not too large. 20. Assume the square matrices matA() and matB() have the same size. Given a positive integer n, assign to matB() the nth power of the matrix matA(). 21. Assume the matrices matA(), matB(), and matC() Assign to matC() the sum of matA() and matB().

have the same size.

22. Assume the matrices matA() and matB() have been dimensioned with the statements DIM matA(1 TO m, 1 TO n) and DIM matB(1 TO n, 1 TO m). Assign to matB() the transpose of matA(). 23. Assume the matrices matA() and matB() number c, assign c times matA() to matB().

have the same

size. Given

a

In Exercises 24 through 31, write a program to perform the stated task. 24. A company has two stores (1 and 2), and each store sells three items (1, 2,

and 3). Table 7.22 and Table 7.23 give the inventory at the beginning of the day and the amount of each item sold during that day. Item

Item

1 St

ne

Table 7.22

Dor

wOAU

eee

E23

Beginning Inventory

S

Uet4or

cuen2a'

Table 7.23

2

e

24

3 11

18

Sales for Day

(a) Record the values of each table in an array. (b) Adjust the values in the first array to hold the inventories at the end of

the day and display these new inventories. (c) Calculate and display the total number of items in the store at the end of the day.

25. Table 7.24 gives the composition of 100 grams of a chemical substance and the amount (in grams) of its constituents. (a) Place the data from the table in an array.

(b) Determine the total amount of Hydrogen used.

TWO-DIMENSIONAL ARRAYS

7.4

= 333

Hydrogen

Oxygen

Sodium

Chlorine

Substance

(H)

(O)

(Na)

(Cl)

Water (H,O) Salt (NaCl) Hydrogen Chloride (HCl) Caustic Soda (NaOH)

Lhd 0.0 2.74 BS

88.89 0.0 0.0 40.0

0.0 39.35 0.0 7D

0.0 60.65 97.26 0.0

Table 7.24

Chemical Composition of a Substance

26. A university offers 10 courses at each of three campuses. The number of students enrolled in each is presented in Table 7.25. (a) Find the total number of course enrollments on each campus. (b) Find the total number of students taking each course.

Course

Li

Campus

Table 7.25

1 a 3

De PLY be

2

3

4

le 823) OAL

iZZaee 031 320

2 23, SG2e

5

6

ts

2 25 32 7 35, h25e 426)

Oe 32 229

8

9

10

ee 8 er Ieee

ee ae

Number of Students Enrolled in Courses

27. A state highway department is interested in the variation of two-lane highways. By measuring the width of all two-lane concrete roads, the data containing in Table 7.26 were collected. The first array represents the data and the second one represents the frequency of each measurement. Note that the frequency of each number in a row of array 1 is entered in the corresponding column in array 2. Place the measurements and the frequencies in two arrays and compute the mean value of the width of a two-lane highway. Measurements (meters)

eh. Oh) Bete th es Aeyh 64) 109766 95 67, OS eed OO iV ie 12

Table 7.26

Frequency

6s) 268 ei3

2 1 l 3

5 4 2 4 6

4 l 2D 1 1

Width of Two-Lane State Highways

28. Table 7.27 gives the number of stores for 1991 and 1992 for the five leading retail franchises

(a) Place the data into an array. (b) Calculate the total change companies.

in the number

of stores for these five

334

= Arrays

1. 7-Eleven 2. True Value 3. Ace Hardware 4. ServiStar 5. Radio Shack

Table 7.27

1991

1992

6500 7000 52001" 4500 6746

6395 6800 85200 4500 6756

Number of stores for Leading Retail Franchises

Source: Stores, May 1993

29. The scores for the top three golfers at the 1992 PGA Championship are shown in Table 7.28. (a) Place the data into an array.

(b) Compute the total score for each player. (c) Compute the average score for each round.

Round 1

Nick Price Jim Gallagher, Jr. John Cook Table 7.28

Z

3

4

10 safe T2663 Lie ee

68" 72 eed

70 10 Gare

1992 PGA Championship Leaders

30. Table 7.29 contains part of the pay schedule for federal employees. Table 7.30 gives the number of employees of each classification in a certain division. Place the data from each table into an array and compute the amount of money this division pays for salaries during the year.

Step

GS-1 GS-2 GS-3 GS—4 GS-5 GS-6 GS-7 Table 7.29

1

Z

3

4

11,903 13,382 14,603 16,393 18,340 20,443 PRIA:

£2300 13,701 15,090 16,939 18,951 21,124 23,474

12,695 14,145 15577 17,485 19,562 21,805 24,231

13,090 14,521 15,064 18,031 20,173 22,486 24,988

1993 Pay Schedule for Federal White-Collar Workers

Table 7.30

NH

at

OP

WR

ke Ware

ODOANDN W

Gare) — Coot) Or

ce UN CoG

aS

GS-1 GS-2 GS-3 GS-4 GS-5 GS-6 GS-7

= 335

fh

TWO-DIMENSIONAL ARRAYS

7.4.

Number of Employees in Each Category

31. Consider Table 7.20, the rankings of program that places the data into an be input, and gives the categories in might appear more than once or not

three university departments. Write a array, allows the name of a college to which it appears. Of course, a college at all.

32. A company has three stores (1, 2, and 3), and each store sells five items (1, 2, 3,4, and 5). Table 7.31 and Table 7.32 give the number of items sold by each

store and category on a particular day, and the cost of each item. (a) Place the data from the left-hand table in a two-dimensional array and the data from the right-hand table in a one-dimensional array. (b) Compute and display the total dollar amount of sales for each store and for the entire company. Item

1 Le 25) 2) 1 34s

Store

Table 7.31

2 3 4 O4ee 23 ao C2 el Sen O4uaN 122 A 48s

Item Cost

5 Oo 85

Number of Items Sold During Day

1 Z 3 ~

$12.00 $17.95 $95.00 $86.50

5

$78.00

Table 7.32

Cost per Item

33. Suppose a course has 15 students enrolled and five exams were given during the semester. Write a program that accepts each student’s name and grades as input and places the names in a one-dimensional array and the grades in a two-dimensional array. The program should then display each student’s name and semester average. Also, the program should display the median for each exam. (For an odd number of grades, the median is the middle grade. For an even number of grades it is the average of the two middle grades.) 34. An n-by-n array is called a magic square if the sums column, and each diagonal are equal. Write a program array is a magic square and use it to determine if either is a magic square. Hint: If at any time one of the sums others, the search is complete. (a)

fat 12 6 SaeeOe 13 3

ti 7 ll 2

4 Y 5 16

(by

of each row, each to determine if an of the arrays below is not equal to the

ero Ad) ESiniel2 6 25-0 TS LAO §) Bie he

EER 5 24 7 i a4 8 isis is

336

Arrays

ng duri city aska Nebr cal typi a for n atio ipit prec hly mont the gives 7.33 e Tabl . 35 a five-year period. Write a program that reads the table from DATA statements into an array and then produces the output shown below. [run] precipitation

Total

1986 1987 1988 1989 1990

year

each

for

36.53 31.59 28.56 31.96 22.81

Average precipitation for each May Apr Mar Feb Jan

0.77

1.91

(0-91.

52:94..4.33

Jan. Feb. Mar. 0.88 1.11 2.01 0.76 0.94 2.09 0.67 O80 1.75 0.82.40/80 | 1199 10.7 2 60.00 ie

1986 1987 1988 1989.” 199012 Table 7.33

Apr. 3.64 3.29 2:70 3.05 O02

month Jun

Jul

Aug

Sep

Oct

Nov

4.08"

3.62

4:10

3.50,

2.09")

14 32500.77

May June July 6.44 5.58 4.23 4.68 3.52 3.52 4.01 3:88 3-72 4.19'°4.44°13.98 31233 M2987 65)e

Aug. Sept. 4.34 4.00 4.82 3.72 3:78 .3:.55 457° 3.43 7 998255

Oct. 2.05 2.21 VSS 232 299

Nov. 1.48 1.24 PZ) 1.62 S055

Dec

Dec. 0.77 0.80 O61 0.75 0.92

Monthly Precipitation (in inches) for a Typical Nebraska City

36 . The coordinates of the vertices of an n-sided polygon can be stored in an array dimensioned

with

DIM

vertices(1

TO

n,

1 TO

2). The

x- and

y-coordinates of a starting vertex are assigned to the first row of the array, the coordinates of the vertex to the left of the starting vertex are assigned to the next row of the array, and so on. Write a function that accepts an array of vertices as input and returns the value of the perimeter of the polygon. a4 The Euclidian norm of a matrix is the square root of the sum of the squares of elements of the matrix. Write a function that returns the Euclidian norm of a matrix. SOLU TO TI PRACTICEON PROBLEMS S 7.4 1. The subprogram FindCityNum can be used to determine the subscript associated with each city. This subprogram and the modified subprogram InputCities are as follows: SUB

FindCityNum

SELECT

CASE LET

CASE LET

CASE LET

CASE LET

END

CASE num

"LOS num

"NEW num

=

1

ANGELES" = 2

YORK" = 3

"PHILADELPHIA" num

num)

UCASE$(city$)

"CHICAGO"

SELECT

END SUB

(city$,

= 4

7.5

SUB

A CASE STUDY: CALCULATING WITH A SPREADSHEET

InputCities

(row, col) REM Input origin and destination INPUT "Origin"; city$ CALL FindCityNum(city$, row) INPUT "Destination"; city$

CALL END

337

FindCityNum(city$,

cities

col)

SUB

2. Both parallel arrays and two-dimensional arrays are used to hold related data. If some of the data are numeric and some are string, then parallel arrays must be used since all entries of an array must be of the same type. Parallel arrays should also be used if the data will be sorted. Two-dimensional arrays are best suited to tabular data.

i

*—

A CASE STUDY: CALCULATING SPREADSHEET

WITH A

Spreadsheets are the most popular type of software used on personal computers. A spreadsheet is a financial planning tool in which data are analyzed in a table of rows and columns. Some of the items are entered by the user and other items, often totals and balances, are calculated using the entered data. The outstanding feature of electronic spreadsheets is their ability to recalculate an entire table after changes are made in some of the entered data, thereby allowing the user to determine the financial implications of various alternatives. This is called “What if?” analysis. Figure 7.8 contains an example of a spreadsheet used to analyze a student’s financial projections for the four quarters of a year. Column 5 holds the sum of the entries in the other four columns, rows 4 and 10 hold sums of the entries in rows | through 3 and 5 through 9 respectively, and row 11 holds the differences

of the entries in rows 4 and 10. Since the total balance is negative, some of the amounts in the spreadsheet must be changed and the totals and balances recalculated. This case study develops a menu-driven program to produce a spreadsheet with the five columns of numbers shown in Figure 7.8, three user-specified categories of income, and five user-specified categories of expenses. The following three tasks are to be selected from a menu:

1. Enter data. The user is prompted for three income categories and five expense categories, and for the amounts in each category for each quarter of the year. Then the program should calculate the amounts for totals and balances, display the complete spreadsheet, and display the menu below it horizontally. 2. Alter data. The user specifies each entry to be altered by giving its row, column, and new amount. After each change is entered, the amounts for the totals and balances should be recalculated and the total spreadsheet and menu displayed. The user is then prompted for further changes until he responds to the request for row, column, and new amount with 0, 0, 0. 3. Quit.

338

Arrays

5

Total

1 Fall

2 Winter

3 Spring

4Summer

1 Job 2 Parents 3 Scholarship 4 Total Expenses

1000 200 150 1350

1300 200 150 1650

1000 200 150 1350

2000 0) 0 2000

5300 600 450 6350

Tuition Food Rent Books Misc Total

400 650 600 110 230 1990

0 650 600 0 210 1460

400 650 600 120 300 2070

0 650 400 0 120 1170

800 2600 2200 230 860 6690

11 Balance

—640

190

-720

830

—340

Income

5 6 7 8 9 10

Figure 7.8 Spreadsheet for Student’s Financial Projections

The 55 locations in the spreadsheet that hold amounts are called cells. Each cell is identified by its row and column numbers. For instance, the cell 10, 2 contains the amount 1460.

Designing the Spreadsheet Program In keeping with the top-down approach to problem solving, we break the problem into a small number of basic tasks, each of which will then be broken down further. The first task is the setting up of the fixed labels. After that, a menu is presented with the following three options.

1. Create spreadsheet

2. Revise spreadsheet 3. Quit

The first two menu items are broken down into specific subtasks.

1. Create spreadsheet. To form the spreadsheet, we must request the income and expense categories and amounts from the user, calculate the totals and balances, and then display the resulting spreadsheet; that is, task 1 is divided

into the following subtasks. 1.1 Input income and expense categories 1.2 Input income and expense amounts

1.3 Calculate totals and balances 1.4 Display spreadsheet

2. Revise spreadsheet. The user may request a change in just one of the cells by providing its row and column and the new amount. Then the program will recalculate all the totals and balances and display the revised spreadsheet. That is, task 2 is divided into the following subtasks. 2.1 Input cell (row, column) and new amount 2.2 Calculate totals and balances

2.3 Display spreadsheet

(oe. CASE STUDY: CALCULATING WITHA SPREADSHEET

%339

Notice that tasks 2.2 and 2.3 are the same as tasks 1.3 and 1.4. Since the subprogram that performs tasks 1.3 and 1.4 can also be used for tasks 2.2 and 2.3, respectively, considerable work is saved. Whenever possible, generalpurpose subprograms such as these should be incorporated in the design of a program.

The next step in designing the program is to examine each of the subtasks identified above and decide which, if any, should be divided further into smaller tasks. The input tasks, 1.1, 1.2 and 2.1, are basic, so we won’t divide them any

further; but the calculate and display tasks, 1.3 and 1.4, are more involved. These subtasks can be broken down as follows. 1.3 Calculate totals and balances. This subtask requires computing income and expense totals for each of the time periods, computing balances for the time periods, and a “row total” corresponding to each income and expense category of the spreadsheet. 1.3.1

Calculate income totals

1.3.2 Calculate expense totals 1.3.3 1.3.4

Calculate balance Calculate row totals

1.4 Display spreadsheet. To display the spreadsheet, we need to produce the table in Figure 7.8 that contains labels for the income and expense categories and time periods, and has its data arranged in rows and columns. 1.4.1 Display labels 1.4.2 Display data The top-down chart in Figure 7.9 shows the stepwise refinement of the problem. The items in the main part of the chart that are contained in rectangles have continuations below.

Manage a Spreadsheet

Set Up Labels

Present Menu &

Create Spreadsheet

Revise Spreadsheet

Quit

Calculate Totals and Balances

Display

Get Choice

Input Income and Expense Categories

Input Income and Expense Data

Calculate Totals and Balances

Display Spreadsheet

Input New Income and Expense Data

Calculate Totals and

Display Spreadsheet

Balances

Calculate Income Totals

Figure 7.9

Calculate Expense Totals

Calculate Balances

Spreadsheet

Calculate Totals for Rows

Top-Down Chart for Spreadsheet Case Study

Display Labels

Display Data

340

Arrays

Pseudocode for the Spreadsheet Program The workhorse of the top-down chart is the third row. The following pseudocode shows how these tasks are carried out. INPUT INCOME Clear the screen FOR row counter Prompt user for NEXT Display one blank FOR row counter Prompt user for NEXT INPUT INCOME Display two blank FOR row counter Prompt user for NEXT Display one blank FOR row counter Prompt user for NEXT

AND EXPENSE CATEGORIES

(Subprogram InputCategories)

from 1 to 3 income label corresponding to row counter line from 5 to 9 expense label corresponding to row counter AND EXPENSE DATA (Subprogram InputData) lines from | to 3 income data corresponding to row counter line from 5 to 9 expense data corresponding to row counter

CALCULATE TOTALS (Subprogram CalculateSpreadsheet) Calculate Calculate Calculate Calculate

income totals expense totals balances row totals

DISPLAY SPREADSHEET (Subprogram DisplaySpreadsheet) Display column labels FOR row counter from | to 11 IF row counter is 1 THEN

Display income label END IF IF row counter is 5 THEN Display expenses label END IF IF row counter is 11 THEN Display blank line END IF

Display row data NEXT INPUT NEW DATA (Subprogram InputNewData) DO Input new data for spreadsheet LOOP UNTIL data okay

Writing the Spreadsheet Program Three arrays suffice to hold the spreadsheet. (See Table 7.34.) Three of the elements of the array rowLabel, the fourth (Total), 10th (Total), and 11th

7.5

A CASE STUDY: CALCULATING WITH A SPREADSHEET

341

(Balance), are fixed. The other elements of that array are the categories to be

determined by the user. The column labels are all fixed. The data for all rows except 4, 10, and 11 must be entered by the user.

Arrays

Range

Information Held

rowLabel$() colLabel$() userData()

LTOT! LOS PO

Job, Parents, ..., Balance Fall, Winter, . . . , Total Amounts in the 55 cells

Table 7.34

tal bes

The Arrays That Hold the Spreadsheet

When values have been assigned to the three arrays, the totals are easily calculated with loops containing accumulators. Then the balances are calculated by performing subtractions. After the user has entered the spreadsheet, he or she is presented with a menu of three options. The user can enter a completely new spreadsheet (with possibly different categories), revise selected data in the current spreadsheet, or quit. The first task is identical to the formation of the original spreadsheet and the last task is trivial. After selecting the update option, the user is asked for a data entry to alter. The entry is specified by giving the location of the entry, namely its row and column, and the value of the entry. After the three responses are obtained, the program recalculates all the totals and balances. The user can continue to revise the spreadsheet to his heart’s content. The user indicates that he or she is finished with the update by responding with 0, 0, 0. Table 7.35 shows each task discussed above and the subprogram that carries out the task. The program follows.

1.

2.

Bx

InputSpreadsheet 1.1 Input income and expense categories 1.2 Input income and expense data 1.3 Calculate totals and balances 1.3.1 Calculate income totals 1.3.2 Calculate expense totals 1.3.3 Calculate balances 1.3.4 Calculate row totals 1.4 Display spreadsheet 1.4.1 Display labels 1.4.2 Display data Revise spreadsheet 2.1 Input new data 2.2 Calculate totals and balances 2.3 Display spreadsheet Out

Table 7.35

Tasks and Their Procedures

InputSpreadsheet InputCategories InputData Calculate CalculateIncomeTotals CalculateExpenseTotals CalculateBalances CalculateRowTotals DisplaySpreadsheet

ReviseSpreadsheet InputNewData Calculate DisplaySpreadsheet

342

~=Arrays

REM

Spreadsheet

Ae

KK

REM

*

REM

*

REM

*

REM REM REM REM

* * * *

REM

*

REM

KKK

IK

KKK

KKK

Program KKK

KKK

KKK

KKK

KKK

KKK

IK

KKK

KKK

KKK

KKK

KKK

KEKEKKKKKKKEK

*

%

Table

Variable

%

User's main menu choice (1, 2, or 3) Column labels (seasons and TOTAL) Numeric data entered by user, totals Row categories entered by user

choice colLabel$() entries() rowLabel$()

* ts * is fe

KK

KEKE

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKKKKKKKKKKKKKEKE

CLS DIM colLabel$(1 TO 5), rowLabel$(1 TO 11), CALL SetUpLabels(rowLabel$(), colLabel$())

entries(1

TO

11,

1 TO

DO

CALL GetChoice(choice) SELECT CASE choice CASE 1

CALL

InputSpreadsheet (rowLabel$(),

colLabel$(),

CASE 2 CALL ReviseSpreadsheet (rowLabel$(), CAS

LOOP REM

entries())

"Have

a nice

day."

SELECT

UNTIL ---

DATA

colLabel$(),

ERS

PRINT END

entries())

choice

Data:

1 Fall,

= 3

column

labels

2 Winter,

3 Spring,

4 Summer,

5 Total

END

SUB Calculate (entries()) REM Calculate totals and balances for spreadsheet CALL CalculateIncomeTotals(entries()) CALL CalculateExpenseTotals(entries()) CALL CalculateBalances(entries()) CALL CalculateRowTotals(entries()) END

SUB

SUB CalculateBalances (entries()) REM Calculate balances FOR col = 1 TO 4 LET entries(11, col) = entries(4, col

NEXT END

SUB

SUB CalculateExpenseTotals (entries()) REM Calculate total expenses FORSCOM = sles Ona, LET total = 0 FOR row = 5 T0 9 LET total = total + entries(row, row

NEXT

LET NEXT END

col)

SUB

entries(10, col

col)

= total

col)

- entries(10,

col)

5)

A CASE STUDY: CALCULATING WITH ASSPREADSHEED

i

SUB

CalculateIncomeTotals (entries()) REM Calculate total income FOR

col

=

1 T0

LET

total

FOR

row

LET LET

= 0 =

1 TO

total

NEXT

4

3

= total

2col)i=

total

col

END

SUB

SUB

CalculateRowTotals

REM

Calculate

FOR

row

LET

=

total

(entries())

totals

1 TO

for

rows

11

110.4

LET total = total NEXT col LET entries(row, 5) NEXT

all

= 0

FORSCOl=s

END

col)

row

entries (4.

NEXT

+ entries(row,

+ entries(row,

col)

= total

row

SUB

SUB DisplaySpreadsheet (rowLabel$(), colLabel$(), REM Display all spreadsheet information

entries())

GIES

VET asia"

\

PRINT USING a$; LET a$ = "## \ FOR

row

=

SELECT

1 TO CASE

Nor

\

em

colLabel$(1); colLabel$(2); \ #ttttt #HHttHH

Aa

a

Ne

colLabel$(3); colLabel$(4); ainda #ettet #tbtotH"

11 row

CASES

PRINT

CASE

"

Income"

"

Expenses"

5

PRINT

PRINT

CASES! PRINT CASESEESE END

SELECT

REM

The

following

two

lines

should

be

joined

and

PRINT USING a$; row; rowLabel$(row); entries(row, entries(row, 3); entries(row, 4); entries(row, 5) NEXT

row

END

SUB

SUB

EraseLines

REM

Erase

two

LOCATE 21, 1 PRINT TAB(79); WOCAIIE Zn 1 PRINT TAB(79) ; LOCNM2 Zil, il END SUB

lines

near

bottom

of

screen

entered

1);

as

one

line.

entries(row,

2);

colLabel$(5)

343

344

Arrays

SUB GetChoice (choice) REM Input user option HONE Zik dl PRINT "1. Enter data

for

menu

main

Update

2.

Se

data

OUlts

DO HOGATIE 225.01 INPUT "Number of choice: LOOP UNTIL (choice = 1) OR END SUB

(rowLabel$(),

InputCategories

SUB

OR

(choice

= 3)

colLabel$())

labels

category

Input

REM

", choice (choice = 2)

CLS "Income

PRINT row

FOR

INPUT

=

category"

1 TO

3

rowLabel$(row)

"Label";

row

NEXT

rowLabel$(4)

LET

= "Total"

PRINT

PRINT "Expense category" FOR row = 5 10 9 INPUT "Label"; rowLabel$(row) row

NEXT

rowLabel$(10) rowLabel$(11)

LET LET END

SUB

SUB

InputCategoryData

REM

Input

FOR

col

PRINT INPUT

amounts

= "Total" = "Balance"

(colLabel$(), for

one

entries(),

row)

category

= 1 T0 4

USING " \ \: "3; colLabel$(col); "", entries(row, col)

col

NEXT SUB

END

SUB InputData (rowLabel$(), colLabel$(), entries()) REM Input numeric data for entire spreadsheet PRINT PRINT

FOR

row

=

1 10

3

PRINT "Enter each season's income from "; rowLabel$(row) CALL InputCategoryData(colLabel$(), entries(), row) NEXT

row

PRINT

FOR

row = 5 T0 9 PRINT "Enter each season's expenses CALL InputCategoryData(colLabel$(),

NEXT END

SUB

row

for "; rowLabel$(row) entries(), row)

Programming Projects

SUB

InputNewData

REM

Input

(row,

row,

col,

column,

345

newData)

and

new

amounts

for

spreadsheet

update

DO CALL

EraseLines

PRINT

“Enter

INPUT

"Row,

0,

0 to

Column,

LOOP

UNTIL

CALL

EraseLines

END

0,

(row

>=

0)

terminate"

New

data:

AND

(row

",

=

0)

AND

(col

year(index + 1) THEN CALL SwapData(name$(), year(), index) END IF NEXT index NEXT passNum END SUB

SUB SwapData (name$(), year(), index) REM Swap names and years SWAP name$(index), name$(index + 1) SWAP year(index), year(index + 1) END

SUB

SUB WriteData (name$(), year(), REM Write data back into file OPEN

"YOB.DAT"

FOR

OUTPUT

AS

numPeople) #1

FOR i = 1 TO numPeople WRITE #1, name$(i), year(i) NEXT

CLOSE END

7

#1

SUB

If the program from Example 4 of Section 8.1 is executed after running the program in Example 1, the output will be Name

Age

Johnny Ringo

68 54

Barbra Sylvester

52 48

in

1994

370

Sequential Files

Merging Sequential Files In Section 7.2, we considered an algorithm for merging two arrays. This same algorithm can be applied to merging two ordered files provided each file ends with a trailer value. (Relying on the EOF function instead of trailer values requires contorted code.) Trailer values are easily added after opening the files FOR APPEND. Suppose you have two ordered files (possibly with certain items appearing in both files) ending with the same trailer value, and you want to merge them into a third ordered file (without duplications). The technique for creating the third file is as follows. 1. Add a trailer value to the end of each file.

2. Open the two ordered files FOR INPUT and open a third file FOR OUTPU 3. Get the first item from each file.

4. Repeat steps (a) and (b) below until one of the items retrieved is a trailer value.

(a) If one item precedes the other, write it into the third file and get the next item from its file. (b) If the two items are identical, write one into the third file and get the next item from each of the two ordered files.

5. At this point, the item most recently retrieved from one file may not be the trailer value. In this case, write that item and all remaining items preceding the trailer value to the third file. 6. Close the three files.

EXAMPLE

2

The following program merges two ordered files of numbers into a third file. REM

Merge

CLS INPUT INPUT INPUT

two

"Name "Name "Name

ordered

files

of first file"; filel$ of second file"; file2$ of merged file"; file3$

LET

trailer

= -1

OPEN

filel$

FOR

APPEND

AS

#1

OPEN

file2$

FOR

APPEND

AS

#2

WRITE

#1,

trailer

WRITE

#2,

trailer

CLOSE

#1,

#2

OPEN filel$ FOR INPUT AS #1 OPEN file2$ FOR INPUT AS #2 OPEN file3$ FOR OUTPUT AS #3 INPUT #1, numl INPUT #2, num2

8.2"

DO WHILE

numl

SELECT

CASE

numl

IS

CASE

trailer

num2

371

trailer

< num2

numl

#3,

WRITE

#1, numl > num2

INPUT CASE IS WRITE

#3,

num2

INPUT

#2,

num2

WRITE

#3,

numl

INPUT

#1,

numl

INPUT #2, SELECT

num2

num2

CASE

END

AND

USING SEQUENTIAL FILES

LOOP DO WHILE

numl

WRITE

#3,

numl

INPUT

#1,

numl

LOOP DO WHILE

num2

WRITE

#3,

num2

INPUT

#2,

num2

trailer

trailer

LOOP CLOSE END

#1,

#2,

#3

Control Break Processing Suppose a small real estate company stores its sales data for a year in a sequential file in which each record contains four fields: month of sale (1 through 12), day

of sale (1 through 31), address, price. Typical data for the sales of the first quarter of a year are shown in Figure 8.6. The records are ordered by date of sale.

Figure 8.6

Month

Day

Address

Price

January January January February February March

9 20 25 15 23 15

102 Elm Street 1 Main Street 5 Maple Street 1 Center Street 2 Vista Drive 205 Rodeo Circle

$203,000 $315,200 $123,450 $100,000 $145,320 $389,100

Real Estate Sales for First Quarter of Year

Figure 8.7 shows the output of a program that displays the total sales for the quarter year, with a subtotal for each month.

372

Sequential Files

[run] January January January

for January:

$641,650

1 Center Street 2 Vista Drive

$100,000 $145,320

Subtotal 15 23

February February

for

Subtotal March

15 -

Total

Figure 8.7

for

$203,000 $315,200 $123,450

102 Elm Street 1 Main Street 5 Maple Street

9 20 25

205 Subtotal

First

$245,320

February:

Rodeo

Circle

$389,100

for March:

Quarter:

$389,100

$1,276,070

Output of Example 3

A program to produce the output of Figure 8.7 must calculate a subtotal at the end of each month. The variable holding the month triggers a subtotal whenever its value changes. Such a variable is called a control variable and each change of its value is called a break.

EXAMPLE 3

Write a program to produce the output of Figure 8.7. Assume the data of Figure 8.7 are stored in the sequential file HOMESALE.DAT.

SOLUTION

The following program allows for months with no sales. Since monthly subtotals will be printed, the month-of-sale field is an appropriate control variable. REM Display home sales by month CLS OPEN "HOMESALE.DAT" FOR INPUT AS #1

LET format$ = "\ LET format2$ LET

month

\ ##

= "

‘Adjust

\ Subtotal

NOT

for \

\

EOF(1)

#1,

‘Flag

to

IF

S###, HHH"

indicate

THEN

newMonth$,

day,

addr$,

price

EESE END

necessary

= 0

INPUT LET

as

\ S###, ###"

LET month$ = "" LET done = 0 DO WHILE done = 0 IF

path

done

= 1

Manel

One Wise

end

of

list

8.2

IF

(newMonth$ month$) IF month >= 1 THEN

OR

(done

= 1)

USING SEQUENTIAL FILES

THEN

373

‘Control break processing ‘Don't print on first month

PRINT PRINT

USING

format2$;

month$

+ ":";

monthTotal

PRINT

END IF LET month$

= newMonth$

month

LET

monthTotal

END IF IF done

+

= month

LET

1

= 0

= 0 THEN

PRINT

USING

LET yearTotal

format$;

newMonth$;

= yearTotal

END

IF

LET

monthTotal

monthTotal

#1 USING

for

LOOP CLOSE PRINT END

"Total

First

day;

addr$;

price

+ price + price

Quarter:

$#,###,###";

yearTotal

Comments:

1. DOS has a command called SORT that orders the records of a sequential file. The command SORT

filename2

sorts the records of the first file in ascending order by the first field and places them into a new file called filename2. The DOS command SORT

filename2

/R

produces a descending sort.

PRACTICE PROBLEMS 8.2 1. The program in Example 2 contains three DO loops. Explain why at most one of the last two loops will be executed. Under what circumstances will neither of the last two loops be executed? 2. Modify the program in Example 2 so that duplicate items will be repeated in the merged file.

EXERCISES 8.2 Exercises 1 through 4 are related. They create and maintain the sequential file AVERAGE.DAT to hold batting averages of baseball players. 1. Suppose the season is about to begin. Compose a program to create the sequential file containing the name of each player, his times at bat, and his number of hits. The names should be entered by input statements and the times at bat and number of hits initially should be set to 0.

374

Sequential Files

2. Each day, the statistics from the previous day’s games should be used to update the file. Write a program to read the records one at a time and allow the user to enter the number of times at bat and the number of hits in yesterday’s game for each player in response to INPUT statements. The program should update the file by adding these numbers to the previous figures. . Several players are added to the league. Compose a program to update the file.

. Compose a program to sort the file AVERAGE.DAT with respect to batting averages and display the players with the top ten batting averages. Hint: The file must be read once to determine the number of players and again to load the players into an array. Exercises 5 through 7 are related. They create and maintain the sequential file NUCLEI.DAT

to hold data of radioactive nuclei.

5. The number of radioactive nuclei in any sample of radioactive material decreases continuously as the nuclei disintegrate. The rate at which the number decreases, however, varies widely for different nuclei. If No is the number of nuclei at time t = 0, then the number of nuclei at time t is given by N(t)

= Noe™

where A is the rate of disintegration. The half life T,;) of a radioactive sample is defined as the time required for the number of nuclei to decrease to half the number at t = 0.

Typ = LOG(2)—A. Compose a program to create a sequential file containing radioactive ele-

ments and the values of No and T/7. The data should be entered by INPUT statements. Test the program with the data in Table 8.3.

Element

T 1/2 (days)

No

4475 1920 138

200 175 150

Tritium (H?) Cobalt (Co®°) Polonium (Po?!®) Table 8.3. Activity of Radioactive Elements

6. Each day, the amount of radioactive nuclei decreases. Write a program to calculate the amount of nuclei remaining after 100 days (calculate the value

ofN at t = 100) and update the value of No to N in the sequential file.

7. Several elements (with their corresponding No and T, j2) are to be added to the list. Compose a program to update the file.

82)

USING SEQUENTIAL FILES

375

Exercises 8 and 9 refer to the ordered file BLOCK.DAT containing the names of people on your block and the ordered file TIMES.DAT containing the names of all people who subscribe to the New York Times.

8. Write a program that creates a file consisting of the names of all people on your block who subscribe to the NY Times. . Write a program that creates a file consisting of the names of all NY Times subscribers who do not live on your block. 10. The file DENSITY.DAT contains the names and the densities of five metals in the following order: Brass, 8.6, Gold, 19.3, Mercury, 13.6, Platinum, 21.4, Silver, 10.5. The file DENSITY1.DAT is similar to the file DENSITY.DAT but contains the following metals with their densities: Brass, 8.6, Mercury,

13.6. Write a program to create a file consisting of the information in DENSITY.DAT but with the information contained in DENSITY1.DAT deleted. After the deletions, the new file should have the name DENSITY.DAT. 1

Suppose a file of positive integers is in ascending order. Write a program to determine the maximum number of times any integer is repeated in the file. (For instance, if the entries in the file are 5, 5, 6, 6, 6, and 10, then the output iso)

12; Several kinds of rocket propellants, coded as A, B, C, ... are being tested.

Each record of the file TEST.DAT contains one of the code letters and the burn rate from test firing the rocket. The records are ordered by the code letters. Write a program to display the code letter, number of tests, and average burn rate for each propellant. The program should also display the total number of tests conducted and the average burn rate of all propellants. For instance, if the first four records of the file are BENS) eo “B29 SCE30)

then the first two entries of the output would be [run] Propellant

Number

Average

of Tests

Burn

A

2

33

B

1

29

Rate

Ley, An elementary school holds a raffle to raise funds. Suppose each record of the file RAFFLE.DAT contains a student’s grade (1 through 6), name, and

the number of raffle tickets sold, and that the records are ordered by grade. Write a program using a control break to display the number of tickets sold by each grade and the total number of tickets sold.

376

Sequential Files

AT .D US NS CE file l tia uen seq ted sor the e pos Sup . aks Bre l tro Con 14. Multiple

m for the has ord rec h eac re whe te, sta a of nts ide res all contains names of

h oug thr s pas one in , ine erm det to m gra pro a te Wri ”. “lastName”,“firstName te: (No e. nam full on mm co t mos and me na last on mm co t mos the file, the

ing urr occ t firs the y pla dis uld sho m gra pro the tie, a of nt eve In the unlikely

name.) For instance, the output might be as follows. [run] The

most

common

last

name

is

Brown

The

most

common

full

name

is

John

Smith

and es nam the ns tai con ER ST MA file the e pos sup 16, and 15 ses rci Exe In phone numbers of all members of an organization, where the records are ordered by name. 15. Suppose the ordered file MOVED contains the names and new phone numbers of all members who have changed their phone numbers. Write a program to update the file MASTER.

16. Suppose the ordered file QUIT contains the names of all members who have left the organization. Write a program to update the file MASTER. 17. Suppose a file must be sorted by QBasic, but is too large to fit into an array. How can this be accomplished? 18. What are some advantages of files over arrays?

19. Do the following steps at the computer. (a) Create a sequential file HOMES

containing the five records Huron,

Ontario, Michigan, Erie, and Superior in the given order. (b) Execute the command

Exit from the Files menu. You will now be in

DOS. (c) Enter the command TYPE HOMES to see the Great Lakes displayed in the given order. Their first letters should spell HOMES. (d) Enter the command

SORT

HOMES

to order the great

lakes. (e) Enter TYPE HOMES to see the Great Lakes displayed in alphabetical order. SOLUTIONS TO PRACTICE PROBLEMS 8.2 1. Execution proceeds beyond the first DO loop only after a trailer value is read from one of the input files. Since each of the following DO loops executes only if the trailer value of the associated file was not read, at most one loop can execute. Neither of the loops will be executed if each input file contains only the trailer value or if the last entries of the files are the same.

2. Change the SELECT CASE block to the following: SELECT CASE

numl

IS num2

WRITE

#3,

num2

INPUT

#2,

num2

SELECT

A-GASE STUDY: CREATING AIREGEIPT

oo

8, 3

S77

A CASE STUDY: CREATING A RECEIPT Most supermarkets have automated check-out counters. Scanners read coded information on each item and send the information to a computer that produces an itemized receipt after all the items have been scanned. This case study develops a program to produce an itemized check-out receipt after all the coded information has been entered. The standard code is the Universal Product Code (UPC), which consists of

a sequence of 10 digits appearing below a rectangle of bars. (See Figure 8.8.) The bars have these digits encoded in a form that can be read by an optical scanner. The first five digits encode the manufacturer and the second five digits specify the product and the size of the package. The digits 37000 00430 appear on a jar of peanut butter. The string 37000 is the code for Procter & Gamble and 00430 is Procter @ Gamble’s code for a 22-ounce jar of creamy Jif peanut butter. Of course, the string 00430 will have an entirely different meaning for another

|

Figure 8.8

37000°

00430

Universal Product Code

Suppose a supermarket carries four thousand items and a sequential file called MASTER.DAT holds a record for each item consisting of the following information: the UPC, the name of the item, the price. Let us also assume the file has been sorted by the UPC for each record and that the file ends with a sentinel record whose fictitious UPC is greater than any actual UPC. (Note: The use of a sentinel is a common practice when an entire file will be read sequentially. The advantage of using a sentinel, as opposed to relying solely on EOF, will become apparent when the program is written.) For instance, the file might contain the following data for three food items. "3700000430","22-0z "4119601012","19-0z

Jif Peanut Butter",1.76 Prog Minn Soup",1.19

soz sCSmC inn 53 07m 0 “70/34 "9999999999", "Sentinel",0

ROS@mlea)

1.65

We wish to write a program that will accept as input UPC codes entered from the keyboard and produce as output a printed itemized receipt. One way to proceed would be to take each UPC as it is input into the computer and then search for it in the master file to find the item description and price. We then would have to search sequentially through a long file many times. A better way to proceed is to first store the input UPCs in an array and then sort the array in increasing order, the same order as the master file. Then the information can be located in just one sequential pass through the master file.

378

Sequential Files

The program must be able to handle the special case in which a UPC code entered is not in the master file. Suppose the first array item, after the array of UPCs has been sorted, is not in the master file. Then its UPC will never equal one of the UPCs in the master file. At some point during the sequential pass through the master file, the array UPC will be less than the most recently read UPC from the master file. This indicates that the UPC is not in the master file, and that the user must be informed of this fact. After the array of UPCs has been sorted, the search algorithm is as follows.

1. Begin with the first (lowest) array item. (It is most likely higher than the first UPC in the master file.)

2. Read records from the master file until the record is found whose UPC matches or exceeds the array UPC.

3. If the master file UPC matches the array UPC, then print the corresponding description and price of the item from the master file and add the price to the running total. Otherwise, print a message stating that the item is not in the master file.

4. Repeat steps 2 and 3 for each element of the array.

Designing the Supermarket Check-Out Program The major tasks of the program are as follows:

1. Input UPC codes from the keyboard (and count number of items). Task 1 uses a loop that requests the UPCs of the items purchased. A counter should keep track of the number of items purchased and a sentinel should indicate when all the UPCs have been entered. 2. Sort the array of UPC codes into ascending order. Task 2 can be accomplished with a bubble sort since the array is small. 3. Create an itemized receipt. Task 3 can be divided into smaller subtasks. After the master file is opened, the file is searched sequentially for the triplet holding the first array UPC. If this record is found, the item name and price are printed and the price is added to the total. Then, the second item is looked for in the same manner. This process continues until all possible items and prices have been printed. Of course, any unlocatable item must be reported. Finally, the total price is printed and the master file is closed. That is, task 3 is divided into the following subtasks: 3.1 Open the master file. 3.2 Search for array UPCs in the master file. 3.3 Print an itemized receipt. 3.4 Close the master file.

Figure 8.9 shows the top-down chart for the program.

83

AICASE STUDY: CREATING AREGEIPT

Create Itemized Bill

Reset Master UPC File

Input

Sort

Create

UPC Codes

UPC Codes

Itemized Bill

Search for UPCs in File

Print Bill Entries

Close Master UPC File

Figure 8.9 Top-Down Chart for the Supermarket Check-Out Program

Pseudocode for the Supermarket Check-Out Program INPUT UPC CODES (Subprogram InputCodes) Initialize numItems counter to 0 Prompt user for input DO WHILE there are more items to be entered Read the UPC into the current array element Increment numItems Prompt user for more input LOOP SORT UPC CODES (Subprogram SortCodes) FOR passNum = | TO numltems — 1 FOR i = | TO numltems — passNum IF the ith array UPC is greater than the (i+1)th THEN Switch the ith and (i+1)th array elements

END IF NEXT i NEXT passNum CREATE ITEMIZED RECEIPT (Subprogram MakeReceipt) Open the master file Initialize total to 0 Read first triplet from the master file FOR i = 1 TO numlItems DO WHILE item i’s UPC > the current file UPC Read the next record from the master file LOOP IF item i’s UPC = the file UPC THEN

Print the corresponding item description and price Increase total by price ELSE Print that the UPC is not in the master file END IF NEXT i Print total Close the master file

9379

380

Sequential Files

Writing the Supermarket Check-Out Program Table 8.4 shows each of the tasks discussed above and the procedure used to perform the task.

1. 2. 3. Table 8.4

Task

Procedure

Input UPCs and count number of items Sort the array of UPCs into ascending order Create itemized receipt

InputCodes SortCodes MakeReceipt

Tasks and Their Procedures

The following program loads the purchased items into an array, sorts the array, and then carries out the search algorithm. A sample run is presented. REM

Print

out

an

itemized

KKK

KK

grocery

bill

REM REM

KKKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKK

KKKKKKKEEK

REMips

*

REM * itemUPC$()

Array of UPC's

REM

* numItems

Counts

REM

*

REM

KR

the

for the items

number

of

items

purchased

_

purchased

i te

KK

KKK

KKK

KK

KKK

KKK

KK

KKK

KKK

KK

KKK

KKK

KK

KKK

KKK

KKK

IK

KKK

KK

KKK

KKKEK

REM DIM

itemUPC$(1

TO

100)

CLS CALL InputCodes(itemUPC$(), numItems) CALL SortCodes(itemUPC$(), numItems) CALL MakeReceipt(itemUPC$(), numItems) END

SUB InputCodes REM

Fill

LET

numItems

PRINT

the

"Enter

(itemUPC$(), array

with

numItems) UPC

codes

for

items

purchased

= 0 * when

all

items

have

been

entered."

PRINT

INPUT "Enter UPC code DO WHILE code$ "*" LET

numItems

of

= numItems

item: +

",

code$

1

LET itemUPC$(numItems) = code$ INPUT "Enter UPC code of item: LOOP END SUB

",

code$

SUB MakeReceipt (itemUPC$(), numItems) REM Output store receipt REM total Total cost of all purchases REM code$ UPC at the current file position REM descr$ Description of item at current position REM price Price of current item OPEN "MASTER.DAT" FOR INPUT AS #1 LET total = 0 INPUT

#1,

code$,

descr$,

price

‘Read

first

record

from

master

file

Appendix: Displaying the Contents of a File

FOR

1 =

1 TO

DO WHILE

INPUT

381

numItems

itemUPC$(i)

#1,

code$,

> code$

descr$,

price

LOOP

IF itemUPC$(i)

= code$ THEN

LPRINT descr$; TAB(37); price LET total = total + price BESE UPRINT “**. UPCT si temUPCS (ays. 2@not dusted $$###.##"; CLOSE #1 END SUB

SUB SortCodes

(itemUPC$(),

numItems)

REM

Perform

bubble

sort

FOR

passNum

= 1 TO

numItems

FOR

i

=

1 TO

numItems

total

on

the

-

array

1

- passNum

IF

itemUPC$(i) > itemUPC$(i + 1) SWAP itemUPC$(i), itemUPC$(i END IF NEXT 7 NEXT passNum END SUB

THEN + 1)

[run] Enter

* when

Enter Enter Enter Enter Enter

UPC UPC UPC UPC UPC

code code code code code

22-oz

Jif

Peanut

Butter

e716

22-oz

Jif

Peanut

Butter

ev7i6

all

items

of of of of of

item: item: item: item: item:

have

been

7073405307 3700000430 3700000430 4100034200 *

** UPC 4100034200 not listed **

2.5 Total

oz

CS

Cinn

Rose

entered.

Tea

S=Ssessas2asaetasessssS25552>

yee

ee ee printer

ie65 $5.17

Chapter 8 Appendix: Displaying the Contents of a File The following program reads the first 2000 characters of a file requested by the user, and displays them on a graphics monitor. (To run the program with a monochrome display monitor, change the fourth line to DEF SEG = G@HBO00.) Carriage returns appear as single musical notes and line feeds appear as reverseimage circles. Press any key to clear the screen. (This program uses some statements not covered in the text.)

382

Sequential Files

REM

Display

GS INPUT DEF

"FILE

every

TO

READ";

= &HB800

SEG

character

in

a file

to

&HB000

file$ ‘Change

SGREENBO R= Onm0 OPEN file$ FOR INPUT AS #1 CES LET 1 =20 DO WHILE (i 2000) AND (NOT EOF(1)) ‘Read next LET char$ = INPUT$(1, #1) POKE 2 * i, ASC(char$)

for

monochrome

character

display

from

file

1

REbe tes

LOOP #1

CLOSE

LET

a$

= INPUT$(1)

‘Pause

until

a key

is

pressed

END

Chapter 8 Summary 1. Each file has a filespec that gives the disk drive holding the file and the file name. QBasic programs associate a reference number with any file used in a program and refer to the file by that number. . When sequential files are opened, we must specify whether they will be created and written to, added to, or read from by use of the terms OUTPUT,

APPEND, or INPUT. The file must be closed before the operation is changed. Data are written to the file with WRITE# statements and retrieved with INPUT statements. The EOF function tells if we have read to the end of the file.

. A sequential file can be ordered by placing its data in arrays, sorting the arrays, and then writing the ordered data into a file. This process should precede adding, deleting, or altering items in a master file.

Chapter 8 Programming Projects 1. Suppose the sequential file “ALE” contains the information shown in Table 8.5. Write a program to use the file to produce Table 8.6 in which the baseball teams are in descending order by the percentage of games won.

Programming Projects

Team

Won

Lost

82 78 ic 78 65 83 87

70 73 80 14 88 70 64

Baltimore Boston Cleveland Detroit Milwaukee New York Toronto

Table 8.5

383

American League East Games Won and Lost, 9/23/93

American League East Toronto New York Baltimore Boston Detroit Cleveland Milwaukee Table 8.6

W

L

Pct

87 83 82 78 78 73 65

64 70 70 8) 74 80 88

576 42 eyes. OL ps Add 425

American League East Standings on 9/23/93

2. Write a rudimentary word processing program. The program should (a) Request the name of the sequential file to hold the document as input from the keyboard. (b) Clear the screen and display the symbol > as a prompt at the upper left corner of the screen.

(c) Request the first line of the file as input from the keyboard and write this line to the file when the Enter key is pressed. Note: Blank lines are acceptable input, but lines exceeding 60 characters in length should not be accepted (the user should be prompted to reenter the line). (d) Display a second prompt at the leftmost position of the next line of the screen and carry out (c) for this line. (e) Continue as in (d) with subsequent lines until the user responds with EOD. (EOD should not be written to the file.) (f) Clear the screen and display the complete text file on the screen. [sample Enter

run] the

name

of

the

file

to

[Screen cleared] >The most important feature !ILINE TOO LONG!! >The most important feature >performs correctly. This is >solution to the problem is

>E0D The

most

performs solution

important

feature

create:

MYFILE

of a computer

program

is

that

it

of a computer program is that it most likely to occur when the systematically planned.

of

a computer

program

is

correctly. This is most likely to occur when to the problem is systematically planned.

that

the

it

performs

384

Sequential Files

3. Write a program that counts the number of times a word occurs in the

sequential file created in Programming Project 3. The file name and word should be input from the keyboard. For instance, opening MYFILE and searching for “is” would produce the output: “is” occurs 3 times. A department store has a file containing all sales transacted for a year. Each record contains a customer’s name, zip code, and amount of the sale. The file is ordered first by zip code and then by name. Write a program to display the total sales for each customer, the total sales for each zip code, and the total sales for the store. For instance, if the first seven records of the file are "Adams,

John", 10023,34.50

"Adams,

John",10023,60.00

"Jones,

Bob",10023,62.45

"Green,

Mary", 12345,54.00

"Howard, Sue",12345,79.25 "Smith, George",20001,25.10

then the output will begin with Customer Adams, John Jones,

Total Sales 94.50

Bob

62.45

Total sales Green, Mary

of zip 54.00

code

10023:

156.95

. Write a program that requests a positive integer as input, generates the prime

factors with the algorithm of Exercise 44 in Section 5.1, and writes these primes to the file PRIMES. (For instance, if the user responds with the number 3240, the file PRIMES will contain the primes 2, 2, 2, 3, 3, 3, 3, 5

in that order.) The program should then read the file PRIMES and produce a table showing each prime and its multiplicity. A sample output is as follows. [run] Enter Prime

2 3 5

a positive

integer:

3240

Multiplicity

3 4 1

Light consists of electromagnetic waves having a speed of propagation c = 3- 10° meters per second, but differing in frequency f and wavelength lambda. The general wave relation

c = lambda - f holds for each wave. Table 8.7 shows the wavelengths for colors in the visible spectrum. Write a program to place this data into a sequential file. Then write a second program to use the sequential file to create the output shown in Figure 8.10. Calculate the frequency range of each wave in the spectrum using the formulas fax = ¢/lambda,,i,

fmin = c/lambda,,,.

Programming Projects

385

For instance, for violet,

fee

oR Ou (400. 10 uae fo = 3. 108/(450 - 10-?) Color

Table 8.7

Figure 8.10

lambda,

;,,(nm)

lambda,,,,, (nm)

violet blue green yellow

400 450 500 550

450 500 Spy 600

orange

600

650

red

650

700

Visible Spectrum (nm denotes nanometers)

Wavelengths (nanometers) 400 to 450

Color

Max.

Freq.

Min.

Freq.

violet

750.00E+12

666.67E+12

450

to

500

blue

666.67E+12

600.00E+12

500

to

550

green

600.00E+12

545.45E+12

550 600 650

to to to

600 650 700

yellow orange red

545.45E+12 500.00E+12 461.54E+12

500.00E+12 461.54E+12 428.57E+12

Output for Project 6

7. Create and Maintain an Astronomical Data File. Use the data in Table 8.8 to

write a menu-driven program that performs the following tasks: (a) Create a sequential file consisting of the names, magnitudes, distances, and locations of several stars. The information should be supplied in response to INPUT statements. (b) Display the information in the sequential file. (c) Delete a star and the corresponding magnitude, distance, and location from the sequential file. (d) Add a star and its corresponding magnitude, distance, and location to the sequential file.

386

Sequential Files

Name Sirius Canopus Rigil Arcturus Vega Capella Rigel Procyon Achernar Altair Betelgeuse Aldebaran Spica Antares Pollux Fomalhaut Deneb

Magnitud

Distance (light-years)

Location (constellation)

—1.60 —0.73 —0.20 —0.06 0.04 0.08 0.11 0.50 0.48 Oe 0.80 0.85 0.96 1.00 145 1.16 eas)

9 650 540 36 UG 45 900 11 118 16 520 68 220 520 35 23 1600

Canis Major Carina Centaurus Bootes Lyra Auriga Orion Canis Major Eridanus Aquila Orion Taurus Virgo Scorpio Gemini Piscis Austrinis Cygnus

Table 8.8 Seventeen Brightest Stars Source: New York Public Library Desk Reference

8. Table 8.8 gives information about the 17 brightest stars. (The magnitude of a star is a measure of its brightness. The lower the magnitude, the brighter the star. The sun has a magnitude of —26.7.) Suppose each line of the table has been placed in the sequential file STARS with the statement WRITE

#1,

name$,

magnitude,

distance,

location$

Write a program to read the file into four parallel arrays, sort the arrays by the names of the stars, repeatedly accept the name of a star as input, and use a binary search to locate the star and display the three pieces of information about the star. A sample outcome is as follows: [run] (Enter * to exit the program.) Enter the name of a bright star: Magnitude:

.11

Distance: Location:

900 Orion

Rigel

(Enter * to exit the program. ) Enter the name of a bright star: Ras Algethi Ras Algethi is not one of the 17 brightest stars. (Enter * to exit the program.) Enter the name of a bright star:

*

Programming Projects

387

9. A fuel economy study was carried out for five models of cars. Each car was driven for 100 miles of city driving, then the model of the car and the number of gallons used were placed in the sequential file MILEAGE with the statement WRITE

#1,

model$,

gallons

Table 8.9 shows the first entries of the file. Write a program to display the models and their average miles per gallon in decreasing order with respect to mileage. The program should utilize three parallel arrays of range 1 TO 5. The first array should record the name of each model of car. This array is initially empty; each car model name is added when first encountered in reading the file. The second array should record the number of test vehicles for each model. The third array should record the total number of gallons used by that model. Note: The first array must be searched each time a record is read to determine the appropriate index to use with the other two arrays.

Model

Gal

Model

Gal

Model

Gal

LeBaron Escort Beretta

49 4] 4.3

Cutlass Escort Escort

4.5 3.8 3.9

Cutlass LeBaron Escort

4.6 Sell 3.8

Skylark

4.5

Skylark

46

Cutlass

4.4

Table 8.9 Gallons of Gasoline Used in 100 Miles of City Driving

Random-Access Files (=

9) 6 2060, RETURN S000 -:

options and point values kent or Mortaage Fymt),

oe

1 Over

with

this

Lice

ret

eee

‘To

LET MUPCS = “" ure LET MPRE =O = ~~ ‘Pri 150 REM -- Fian d d n print UPC. d » 2060 OPEN “UPC.DATFO "R INPUT AS INPUT #1. MUPC#. MDES#. MERI

bank? €

Arr

(

LET TOTALPRI = 0

pri

and

name

Print

:

2020

a point value

question, fcount

‘

£700

(==— Sub: RK = 1 LET

arte

y

tt

7

i

Zence

i

ii

&

te

Se

iis 194 1O4 4

j

‘=

z

il

a) aes) a4]

ters

Al

;

HO

af

2

Yi

ee

rigs

=

anal

Bi

a |

| |

|

|

4

|

‘

|

7

=

ms) i!

=

a i

|

|‘|

I

is

i

i |

2%

a

ee:

|

|

|

C

“A

a) i

Subroutines

EP:

Le

S

*

f

K

ve

a

|

|

es

1G? 1CGU

S

a

‘

RIT

|

+

FRG RE TUS

g ibe]

iece

| A

| £2 care ca. Petes Spt fee LE BRR

BAe + Po REESE a £ aKa é ,

FER 1

E

e

Pah bb

¥

vf

A

Ie

5

CPE

:

>

‘

‘ eee

F

t

Ee

‘

58

Ae

There are times when we want to consider the values assigned to variables of different types as being the same, such as city and town$ in Example 3. In this situation, the function RTRIM$ comes to the rescue. If a$ is an ordinary string or a fixed-length string, then the value of RTRIM$ (a$)

is the (variable-length) string consisting of a$ with all right-hand spaces removed. For instance, the value of RTRIM$(“hello

”) is the string “hello”. In

Example 3, if the IF block is changed to (RTRIM$(city) = town$) PRINT "same" BLSe PRINT "different" END IF IF

AND

(RTRIM$(city)

= RTRIM$(municipality))

THEN

then the first line of the output will be “same”. Records

We have worked with four different data types in this text: numbers, strings, arrays, and fixed-length strings. Strings and numbers are built-in data types that can be used without being declared. On the other hand, arrays and fixed-length strings are user-defined data types that must be declared with a DIM statement before being used. A record is a user-defined data type that groups related variables of different types. Figure 9.1 shows an index card that can be used to hold data about colleges. The three pieces of data—name, state, and year founded—are called fields. Each

field functions like a variable in which information can be stored and retrieved. The length of a field is the number of spaces allocated to it. In the case of the index card, we see that there are three fields having

lengths 30, 2, and 4,

respectively. The layout of the index card can be identified by a name, such as collegeData, called a record type.

Dae Ate GPBS:

393

Name:

State: _ Year Founded:

Figure 9.1

An Index Card Having Three Fields

For programming purposes, the layout of the record is declared by the block of statements TYPE

collegeData nom AS STRING * 30 state AS STRING * 2 yearFounded AS SINGLE END TYPE

Each character of a string is stored in a piece of memory known as a byte. Therefore, a field of type STRING * n requires n bytes of memory. However, numbers (that is, the single-precision numbers we use in this text) are stored in

a different manner than strings and always use four bytes of memory. A record variable capable of holding the data for a specific college is declared by a statement such as DIM

college

AS

collegeData

Each field is accessed by giving the name of the record variable and the field, separated by a period. For instance, the three fields of the record variable college are accessed as college.nom, college.state, and college.yearFounded. Figure 9.2 shows a representation of the way the record variable is organized.

college

college.nom college.state

college.yearFounded

Figure 9.2

Record Variable with Values Assigned to the Fields

394

Random-Access Files

In general, a record type is created by a TYPE block of the form TYPE

recordType

fieldNamel fieldname2

END

AS fieldTypel AS fieldType2

TYPE

where recordType is the name of the user-defined data type, fieldName], fieldName2, ... are the names of the fields of the record variable, and fieldType1,

fieldType2, . . . are the corresponding field types, either STRING * n, for some n, or SINGLE. A record variable recordVar is declared to be of the user-defined

type by a statement of the form DIM

EXAMPLE 4.

recordVar

AS

recordType

The following program processes records. REM

Demonstrate

use

of

records

CLS TYPE

collegeData

nom AS STRING * 30 state AS STRING * 2 yearFounded

AS

SINGLE

END TYPE DIM college AS collegeData INPUT "Name"; college.nom INPUT "State"; college.state INPUT "Year Founded"; college. yearFounded LET century = 1 + INT(college.yearFounded / 100) PRINT RTRIM$(college.nom); " was founded in the"; century; PRINT "th century in "; college.state DIM university AS collegeData LET university.nom = "M.I.T." LET university.state = "MA" LET university. yearFounded = 1878 IF college.yearFounded < university.yearFounded THEN LET when$ = "before " EESE LET when$ = "after " END IF PRINT RTRIM$(college.nom); " was founded "; PRINT when$; RTRIM$(university.nom) END

[run] Name? Oberlin State? OH

College

Year Founded? 1837

Oberlin

Oberlin

College College

was was

founded founded

in the before

19 th century M.I.T.

in

OH

ON

(DATASEYPES!

395

TYPE statements can only appear in the main body of a program, never in procedures. However, DIM statements can be used in procedures to declare a local record variable. When

records are passed to and from procedures,

parameter in the SUB or FUNCTION parameter

EXAMPLE

5

AS

the

statement must have the form

recordType

The following program uses procedures to perform the same tasks as the program in Example 4. REM

Demonstrate

use

of

records

with

procedures

CLS TYPE collegeData nom AS STRING * 30 state AS STRING * 2 yearFounded AS SINGLE END TYPE DIM college AS collegeData CALL GetData(col lege) CALL DisplayStatement (college) END SUB

GetData

REM

END

(school

Request

the

INPUT

"Name";

INPUT

"State";

INPUT

"Year

AS name,

collegeData) state,

and

year

founded

school.nom school.state

Founded";

school.yearFounded

SUB

SUB DisplayStatement (school AS collegeData) REM Display the name, century founded, and state LET century = 1 + INT(school.yearFounded/100) PRINT RTRIM$(school.nom); " was founded in the"; PRINT

"th

century

in

";

END

PRINT PRINT END SUB

when$

= “after

century;

school.state

DIM university AS collegeData LET university.nom = "M.I.T." LET university.state = "MA" LET university.yearFounded = 1878 IF school.yearFounded < university.yearFounded LET when$ = "before "

BIESE LET

of a school

THEN

"

IF

RTRIM$(school.nom); " was founded when$; RTRIM$(university.nom)

";

Comments:

1. Record variables are similar to arrays in that they both store and access data items using a common name. However, the elements in an array must be of the same data types, whereas the fields in a record variable can be a mixture

396

Random-Access Files

of different data types. Also, the different elements of an array are identified by their indices whereas the fields of a record are identified by a name following a period. 2. If the record variables recVarl and recVar2 have the same type, then all the field values of recVar2 can be assigned simultaneously to recVarl by the statement

LET

recVarl

=

recVar2

3. Statements of the form PRINT

recVar

and INPUT

recVar

are invalid, where recVar is a record variable. Each field of a record must

appear separately in PRINT, INPUT, and READ statements. Also, comparisons involving records using the relational operators , =, , = are valid only with the record fields, and not with the records themselves. 4. In addition to being declared as numeric or fixed-length string data types, the elements of a user-defined variable type can also be declared as other types of records. However, we do not use such structures in this text. 5. An array of fixed-length strings is declared by a statement of the form DIM arrayName (a TO b) AS STRING

* n

6. When fixed-length strings are passed to and from procedures, the corresponding parameter in the SUB or FUNCTION statement must be a variable-length string. 7. The four different types of numeric variables available in QBasic are shown in Table 9.1. Variables can be specified as one of these types by trailing the name with the proper type-declaration tag or using a DIM statement with the appropriate type identifier.

Numeric Type Integer Long integer Single-precision Double-precision

Table 9.1

Type-Declaration Suffix % Se none or ! =

Identifier Used —_ Bytes of in DIM Statement Storage INTEGER LONG SINGLE DOUBLE

2 4 4 8

The Four Types of Numeric Variables

PRACTICE PROBLEM 9.1 1. In Example 4, why was nom used instead of the more common name for the variable to hold the name of the college?

OU

EXERCISES

DATAGIYPES

9.1

In Exercises 1 through 4, determine the output of the program. 1. DIM ocean AS STRING DIM LET LET

river ocean river

PRINT

* 10

2. DIM colour as STRING * 6

AS STRING * 10 = "Pacific" = "Mississippi"

ocean;

LET colour = "Blue" LET color$ = "Red" PRINT colour; color$;

river

END

END

3. TYPE appearance height AS SINGLE weight AS SINGLE eyeColor AS STRING * 5 END TYPE DIM personl AS appearance DIM person2 AS appearance LET personl.height = 72 LET personl.weight = 170 LET personl.eyeColor = "brown" LET person2.height = 12 * 6 LET person2.weight = personl.weight LET person2.eyeColor = "brownish green" IF personl.height = person2.height THEN PRINT "heights are same" END IF PRINT person2.weight IF personl.eyeColor = person2.eyeColor THEN PRINT “eye colors are same" END IF END

4. TYPE testData nom

AS

score

STRING AS

END

TYPE

DIM

student

* 5

SINGLE AS

testData

FORE letOn3 CALL GetScore(student) CALL PrintScore(student) NEXT i REM

DATA

---

Data:

Joe,

18,

names,

Moe,

scores

20,

Albert,

25

END

SUB

GetScore

READ

student.nom,

END

SUB

SUB

PrintScore

PRINT

END

SUB

(student

AS

student.score

(student

student.nom;

testData)

AS

testData)

student.score

colour

397

398

Random-Access Files

In Exercises 5 through 10, determine the errors. 6. DIM state$ AS STRING * 15

5. TYPE zodiac nom AS STRING * 15 sign AS STRING * 11 END TYPE

state$

LET

= "Maryland"

state$

PRINT END

astrology AS zodiac nom = "Michael" sign = "Sagittarius"

DIM

LET LET

END

name

STRING

AS

streetAddress

*

STRING

AS

friend

AS

*

secondWord

15

END

* 15

AS

var2 END

*

5

TYPE

vitamins

10. TYPE STRING

a AS SINGLE

* 5

b AS

NUMBER

AS

STRING

AS

5

*

address

9; TYPE values label

STRING

AS

firstWord

15

cityState AS STRING zip AS SINGLE DIM

print

8. TYPE

7. TYPE address

TYPE

SINGLE

END

TYPE

DIM

minimum

LET

minimum.b

= 200

LET

minimum.a

= 500

PRINT

vitamins

AS

minimum

END

In Exercises 11 through 14, write a TYPE block to declare a user-defined data type of the given name and types of elements. JEU Name: planet; Elements: planetName, distanceFromSun 12. Name: taxData; Elements: SSN, grossIncome, taxableIncome 13. Name: car; Elements: make, model, year, mileage 14. Name: party; Elements: numberOfGuests, address 15; Write a displays commas hold the

program that requests three words as input from the user and then them on the screen in the first three zones without using any in the PRINT statement. Do this by declaring the variables used to words as fixed-length strings of the appropriate length.

16; Write a program to look up data on notable tall buildings. The program should declare a user-defined data type named “building” with the elements “nom”, “city”, “height”, and “stories”. This interactive program should allow the user to input the name of a building and should search through DATA statements to determine the city, height, and number of stories of the building. If the building is not in the DATA statements, then the program should so report. Use the information in Table 9.2 for the DATA statements. Building

City

Empire State Sears Tower Texas Commerce Tower Transamerica Pyramid

New York Chicago Houston San Francisco

Table 9.2

Tall Buildings

Height (ft)

Stories

1250 1454 1002 853

102 110 75 48

RANDOM-ACCESS

9.2

FILES

399

SOLUTION TO PRACTICE PROBLEM 9.1 1. Reserved words may not be used as names of variables. Although name$ can be used in a LET statement, statements such as DIM name AS STRING or DIM name AS STRING * 30 are not valid since “name” is a reserved word.

Q, D: RANDOM-ACCESS

FILES

A random-access file is like an array of records stored on a disk. The records are numbered 1, 2, 3, and so on, and can be referred to by their numbers. Therefore, a random-access file resembles a box of index cards, each having a

numbered tab. Any card can be selected from the box without first reading every index card preceding it; similarly, any record of a random-access file can be read without having to read every record preceding it. One statement suffices to open a random-access file for all purposes: creating, appending, writing, and reading. Suppose a record type has been defined with a TYPE block and a record variable, called recVar, has been declared with a DIM statement. Then after the statement OPEN

"filespec"

FOR

RANDOM

AS

#n

LEN

= LEN(recVar)

is executed, records may be written, read, added, and changed. The file is referred

to by the number n. Each record will have as many characters as allotted to each value of recVar. Suppose appropriate TYPE, DIM, and OPEN statements have been executed. The two-step procedure for entering a record into the file is as follows. 1. Assign a value to each field of a record variable. 2. Place the data into record r of file #n with the statement PUT

#n,

r,

recVar

where recVar is the record variable from step 1.

EXAMPLE

1

The following program COLLEGES. DAT. REM

Create

the

writes

random-access

CLS TYPE collegeData nom AS STRING * 25 state AS STRING * 2 yrFounded AS SINGLE END TYPE CALL CreateFile END

file

three

records

to the random-access

COLLEGES.DAT

"Name

of

college

‘State

where

'Year

college

college

was

is

located

founded

SUB CreateFile REM Create and write three records into the file COLLEGES.DAT DIM college AS collegeData OPEN "COLLEGES.DAT" FOR RANDOM AS #1°LEN = LEN(college)

file

400

Random-Access Files

= 1 T0

recordNum

FOR

3

INPUT "Name of college"; college.nom INPUT "State located"; college.state INPUT "Year founded"; college.yrFounded PUT #1, recordNum, college NEXT recordNum CLOSE #1 END SUB

[run] Name State Year Name State Year Name State Year

of

College

Comm.

Houston

college?

located? TX founded? 1971 of

located?

Area

Milwaukee

college?

Col.

Tech.

WI

founded? of

1912 college? Virginia

Tech

located? VA founded? 1872

The two-step procedure for reading data from a record is as follows: 1. Execute the statement GEG

eo

necvar

to assign record r of file #n to the record variable recVar. 2. Use the field variables of the record variable to either display values with PRINT or to transfer values to other variables with LET. EXAMPLE

2.

SOLUTION —

Write a program to display the entire contents of the random-access file COLLEGES.DAT. REM Access the random-access CLS TYPE collegeData nom AS STRING * 25 state AS STRING * 2 yrFounded AS SINGLE END TYPE CALL DisplayFile END SUB DisplayFile DIM college AS

file COLLEGES.DAT

"Name

of

college

"State

where

‘Year

college

college

was

is

located

founded

collegeData

OPEN "COLLEGES.DAT" FOR RANDOM AS #1 LEN = LEN(college) PRINT "College", , "State", "Year founded" FOR recordNum = 1 TO 3 GET

#1,

recordNum,

PRINT college.nom, NEXT recordNum CLOSE #1 END SUB

college

college.state,

college.yrFounded

9.2

[run] College Houston

State Comm.

College

Milwaukee Area Virginia Tech

Tech.

Col.

RANDOM-ACCESS FILES

Year

TX

1971

WI VA

1912 1872

401

founded

The total number of characters in the file with reference number n is given by the value of the function OF (n)

The number of the last record in the file can be calculated by dividing this value by the record length. The LOF function, rather than the EOF function, should be used to determine when the end of the file has been reached. For instance,

in Example 2 the FOR statement in the subprogram DisplayFile can be written as FOR

i = 1 TO

LOF(1)

/ LEN(college)

Also, the pair of statements LET

lastRecord

PUT

#1,

= LOF(1)

lastRecord

+

1,

/ LEN(college) college

can be used to add a record to the end of the file. Comments:

1.

Random access files are also known as direct-access or relative files. Since each record has the same number of characters, the computer can calculate where to find a specified record and, therefore, does not have to search for

it sequentially.

2. Unlike sequential files, random-access files needn’t be closed between placing information into them and reading from them. 3. Random-access files do not have to be filled in order. For instance, a file can

be opened and the first PUT statement can be PUT #, 9, recVar. In this case, space is allocated for the preceding eight records. 4. If the record number r is omitted from a PUT or GET statement, then the

record number used will be the one following the number most recently used in a PUT or GET statement. For instance, if the line PUT

#1,

, college

is added to the program in Example 2 just before the CLOSE statement, then the information on Virginia Tech will be duplicated in record 4 of the file COLLEGES.DAT. 5. Users often enter records into a random-access file without keeping track of the record numbers. If file #n is open, then the value of the function LOC (n)

is the number of the record most recently written to or read from file n with a PUT or GET statement.

402

Random-Access Files

6. Each record in a random-access file has the same length. This length can be any number from | to 32767. 7. When the statement OPEN “COLLEGES.DAT” FOR RANDOM AS #1 LEN = LEN (college) is typed, the words “FOR RANDOM” can be omitted. The smart editor will insert them automatically. 8. The decision of whether to store data in a sequential file or in a randomaccess file depends on how the data are to be processed. If processing requires a pass though all the data in the file, then sequential files are probably desirable. If processing involves seeking out one item of data, however, then random-access files are the better choice.

PRACTICE PROBLEM 9.2 1. In Example 2, the first PRINT statement clearly displays “State” in the 3rd print zone. Why will the second PRINT statement also display the value of college.state in the 3rd print zone?

EXERCISES 9.2 In Exercises 1 through 8, determine the output of the program. For each of the programs, assume the file COLLEGES.DAT was just created by Example 1, record type collegeData has been declared with a TYPE block, and the first two lines of each of these programs are DIM

college

OPEN

AS

collegeData

"COLLEGES.DAT"

FOR

RANDOM

AS #1

1. GET #1, 3, college PRINT college.state CLOSE

#1

CLOSE END

3. FOR

i = 1 TO LOF(1)

GET

#1,

i,

/ LEN(college)

college

PRINT college.state NEXT i PRINT LOC(1)

CLOSE END

#1

4. LET college.yrFounded PUT

#1,

GET

#1,

PRINT

CLOSE END

2,

= 1876

college

2, college college.nom; #1

5. LET college.nom LET

= LEN(college)

2. GET #1, 3, college PRINT LOF(1); LOC(1)

END

LET

LEN

college.state

college. yrFounded

= "Harvard"

= "MA" college.yrFounded = 1636

#1

9.2

PUT FOR

RANDOM-ACCESS FILES

403

#1, 4, college i = 3 10 4

GET #1, 1, college PRINT college.nom, NEXT i CLOSE #1 END

6. LET college.nom

college.state,

= "Michigan

LET LET

college.state

PUT

#1,

=

FOR@ip

State"

"MI"

college.yrFounded 1,

college.yrFounded

=

1855

college

= al 083

GET

#1,

i,

PRINT

college

college.nom

NEXT i CLOSE #1 END

7GET

#1,

91s college

GET #1, , college PRINT college.nom,

CLOSE END

8. LET

college.state,

college.yrFounded

#1

lastRec

= LOF(1)

/ LEN(college)

GET #1, lastRec, college PRINT college.nom, college.state,

college. yrFounded

#1

CLOSE END

In Exercises 9 through 12, identify the errors. Assume the given code has been preceded with the statements TYPE

filmCredits

nom film

AS

STRING

AS

END

TYPE

DIM

actor

* 25

STRING AS

* 35

"Name

of

actor

"Name

of

film

#2,

CLOSE END 10.

3,

#2

CLOSE END

LEN

= LEN(filmCredits)

actor

#2

OPEN ACTRESS.DAT FOR RANDOM AS #3 LET actor.nom = "Garland" LET actor.film = "Wizard of 0z" LET lastRec = LOF(3) / LEN(actor) PUT

actress

filmCredits

9. OPEN "ACTORS.DAT" FOR RANDOM AS LET actor.nom = "Bogart" LET actor.film = "Casablanca" PUT

or

#3,

lastRec

#3

+

1,

actor

LEN

= LEN(actor)

404

Random-Access Files

1 i OPEN "ACTORS.DAT" actor.nom

LET

actor.film

PUT

#1,

1,

actor

GET

#1,

1,

actor

CLOSE PRINT

RANDOM

AS

#1

LEN

= LEN(actor)

"Stallone"

=

LET

FOR

=

"Rocky"

#1 actor

END

12. OPEN “ACTRESS.DAT" AUN

CLOSE

fills,

Ih,

FOR

RANDOM

AS

#3

LEN

= LEN(actor)

Geile

#1

END

13: Give an OPEN statement and TYPE block for a random-access file named NUMBERS.DAT in which each record consists of three numbers.

14. Give an OPEN statement and TYPE block for a random-access file named ACCOUNTS.DAT in which each record consists of a person’s name (up to 25 characters) and the balance in their savings account. LS: Consider the sequential file YOB.DAT discussed in Section 8.1 and assume the file contains many names. Write a program to place all the information into a random-access file. 16. Write a program that uses the random-access file created in Exercise 15 and

displays the names of all people born before 1970. 17. Write a program that uses determine a person’s year with an INPUT statement, year of birth or report that

the random-access file created in Exercise 15 to of birth. The program should request the name search for the proper record, and either give the the person is not in the file.

18. Write a program that uses the random-access file created in Exercise 15 and adds the data Joan, 1934 to the end of the file.

Exercises 19 through 22 refer to the file COLLEGES.DAT. colleges have been added to the file in no particular order.

Assume many

19; Write a program to allow additional colleges to be added to the end of the file using data entered by INPUT statements. 20, Modify the program in Exercise 19 to insure that the name of the college input has no more than 25 characters. Vass Write a program to find the two oldest colleges. jap, Write a program to display the data on any college requested in response to an INPUT statement. The college should be identified by name and located

by a sequential search of the records. Note: Remember to take into account the fact that each college name retrieved from the file will contain 25 characters. 23: Extend the program in Exercise 22 in the following way: after the information on a college is displayed, exchange its record with the previous record; unless, of course, the displayed record is the first record. (A familiar rule of

Programming Projects

405

thumb for office filing is: 80% of the action involves 20% of the records. After the program has been used many times, the most frequently requested records will tend to be near the top of the file and the average time required for searches should decrease. )

SOLUTION TO PRACTICE PROBLEM 9.2

1. The value of college.nom will have length 25 for each college. Therefore, it will extend into the second print zone and force the value of college.state into the third print zone.

Chapter 9 Summary 1. A fixed-length string is a variable declared with a statement of the form DIM var AS STRING * n. The value of var is always a string of n characters.

. A record is a composite user-defined data type witn a fixed number of fields that either are of fixed-length string or numeric type. TYPE statements define record types and DIM statements are used to declare a variable to be of that type. . After a record type has been specified, the associated random-access file is an ordered collection of record values numbered

1, 2, 3, and so on. Record

values are placed into the file with PUT statements and read from the file with GET statements. At any time, the value of LOF(n) / LEN(recordVar) is the number of the highest record value in the file and the value of LOC is the number of the record value most recently accessed by a PUT or GET statement.

Chapter 9 Programming Projects 1. Balance a Checkbook. Write an interactive program to request information (payee, check number, amount, and whether or not the check has cleared) for each check written during a month and store this information in a

random file. The program should then request the balance at the beginning of the month and display the current balance and the payee and amount for every check still outstanding. . A teacher maintains a random-access file containing the following information for each student: name, social security number, grades on each of two hourly exams, and the final exam grade. Assume the random-access file

406

Random-Access Files

GRADES has been created with string fields of lengths 25 and 11 and three n bee have s ber num rity secu al soci and es nam the all and ds, fiel c eri num entered. The numeric fields have been initialized with zeros. Write a menu-driven program to allow the teacher to do the following. (a) Enter all the grades for a specific exam.

(b) Change a grade of a specific student with data entered using INPUT statements. (c) Print a list of final grades that can be posted. The list should show the

last four digits of the social security number, the grade on the final exam, and the semester average of each student. The semester average is determined by the formula (exam1

+ exam2 + 2 * finalExam) / 4.

Rational Addition. Write a program to add two rational numbers and display their rational sum. A sample output is as follows. [run] Enter

the

numerator

Enter

the

denominator

Enter

the

numerator

Enter

the

denominator

of

the of

of

the

the

of

first

number:

first

second

the

second

8 15

number: number:

number:

3

10

sum is 5 / 6

The

The program should contain the definition TYPE

Rational

num

AS

LONG

den

AS

LONG

END

TYPE

After each rational number is input, the program should check that the denominator is not zero, and then use the greatest common divisor (see Exercise 45 of Section 5.1) of the numerator and denominator to reduce the

rational number to its simplest form. The least common multiple of the two denominators is their product divided by their greatest common divisor. The sum should be displayed in reduced form. The number should be displayed as an integer if the denominator is | or —1, and otherwise as a fraction with a positive denominator.

Graphics

408

1 O

Graphics

i INTRODUCTION

TO GRAPHICS

QBasic has impressive graphics capabilities. Figure 10.1 shows a graph that can be displayed on the screen and printed by the printer.

be Figure 10.1

Graph of the function f(x) = e*sin(20x)

Most monitors can display graphics (such as points, lines, and circles) if the computer contains the proper monitor adapter card. The most common configurations are a graphics monitor attached to a graphics card or a monochrome display attached to a Hercules card. To determine whether your system can support graphics, execute the following program. If you have graphics capabilities, the program will draw a diagonal line. SCREEN 2 LINE (0, 0)-(639, END

199)

Monochrome displays attached to a Hercules card can produce graphics in QBasic provided the program MSHERC.COM is executed from DOS before QBasic is invoked. MSHERC.COM can be found in the DOS directory. (If your computer has both a Hercules graphics card and a color graphics card, enter MSHERC.COM /H from DOS.) To further check the graphics capabilities on a system equipped with a Hercules card, execute the program above with SCREEN 2 replaced by SCREEN 3. Graphics cards have several different display modes. The modes vary in the width of text characters, the number of points that can be displayed horizontally and vertically, and the number of colors available. The two modes always available are referred to as text mode and high resolution graphics mode.

Text Mode: With an appropriate monitor, text can be displayed in 16 different colors specified with the COLOR statement. Text mode is the default mode. It was used in all programs in Chapters 1 through 9.

10.2

SPECIFYING A COORDINATE SYSTEM

409

High Resolution Graphics Mode: Text and graphics can be displayed in the two standard colors of the monitor that we refer to as black and white. Depending

on the monitor, the second color might be green or amber. Text is displayed in 25 eighty-character rows. High resolution graphics mode is invoked with the statement SCREEN 2 (or the statement SCREEN 3 for a monochrome display attached to a Hercules card).

Most monitors purchased within the last four years are VGA monitors, which are capable of utilizing many screen modes. The most useful graphics mode for VGA monitors is very high resolution graphics mode. Very High Resolution Graphics Mode: Text and graphics can be displayed in many colors. Text is displayed in 30 eighty-character rows. Very high resolution graphics mode is invoked on a VGA monitor with the statement SCREEN 12.

The DOS directory contains a program called allows you to print graphics for certain configurations If you intend to print graphics, you must execute this QBasic. The form of the statement depends on the Some variations are:

GRAPHICS.COM that of monitors and printers. program before invoking type of printer you have.

Printer

Command

Dot-matrix printer HP LaserJet compatible printer HP DeskJet printer

GRAPHICS GRAPHICS PASERJET GRAPHICS DESKJET

(See the DOS manual for other variations.) If you want to print the contents of a QBasic graphics screen, press Shift+PrintScreen. This printout is called a screen dump. Comments:

1. All the programs in this chapter contain the statement SCREEN 2. If you are using a monochrome display with a Hercules card, replace this statement with SCREEN 3. With a VGA monitor, you may use SCREEN 12. 2. The SCREEN statement not only specifies a graphics mode, but also clears the screen.

1 O

M

SPECIFYING A COORDINATE

SYSTEM

Suppose we have a piece of paper, a pencil, and a ruler and we want to graph a line extending from (2, 40) to (5, 60). We would most likely use the following

three-step procedure:

410

Graphics

1. Use the ruler to draw an x-axis and a y-axis. Focus on the first quadrant since both points are in that quadrant. 2. Select scales for the two axes. For instance, we might decide that the numbers on the x-axis range from —1 to 6 and that the numbers on the y-axis range from —10 to 80.

3. Plot the two points and use the ruler to draw the straight line segment joining them.

EXAMPLE

1

(a) Draw a coordinate system with the numbers on the x-axis ranging from —2 to 10, and the numbers on the y-axis ranging from —3 to 18. (b) Draw the straight line from (1, 15) to (8, 6). (c) Draw the straight line from (—2, 0) to (10, 0).

SOLUTION

(a)

18

(b)

-3

(c) The point (—2, 0) is the left-hand end-

point of the x-axis and the point (10, 0) is the right-hand endpoint; therefore, the line joining them is just the portion of the x-axis we have pictured.

We draw paper, pencil, steps 1 and 3. values for the

these graphs on the screen with the same three steps we use with and ruler. The only difference is that we first do step 2, and then The QBasic statement WINDOW is used to specify the range of axes and the statement LINE serves as the ruler.

10.2

SPECIFYING

A COORDINATE SYSTEM

411

The statement WINDOW

(a,

c)-(b,

d)

specifies that numbers on the x-axis range from a to b and that numbers on the y-axis range from c to d. (See Figure 10.2.) The ordered pair (a, c) contains the lowest numbers on the two axes and the ordered pair (b, d) contains the highest numbers.

d

a

b

c Figure 10.2

Result of WINDOW

Statement

Figure 10.3

Result of LINE Statement

The statement LINE

(xl, yl)-(x2,

y2)

draws the line segment from the point with coordinates (x1, yl) to the point with coordinates (x2, y2) (see Figure 10.3). In particular, the statement LINE (a, 0)-(b, 0) draws the x-axis and the statement LINE (0, c)—(0, d) draws the y-axis.

The following program produces the graph of Example 1, part (b): SCREEN

2

WINDOW (-2, -3)-(10, LINE (-2, 0)-(10, 0) LINE (0, -3)-(0, 18) LINE (1, 15)-(8, 6)

‘Go

18)

into

high

resolution

graphics,

clear

screen

'Specify coordinate system ‘Draw x-axis ‘Draw y-axis ‘Draw the straight line

END

Note: With a VGA monitor, you may replace SCREEN 2 by SCREEN 12 in this and future programs to obtain a sharper image.

EXAMPLE

2

Consider Figure 10.4. (a) Give the WINDOW statement that specifies the range for the numbers on the axes. (b) Give the statements that will draw the axes. (c) Give the statement that will draw the line.

412

Graphics

Figure 10.4

-10)-(5,

(-1,

(a) WINDOW

SOLUTION

Graph for Example 2 120)

highest x-value

lowest y-value

(b) x-axis:

(-1, 0)-(5,

LINE

desea c

(1,

0)

120)

(0, -10)-(0,

y-axis: LINE

(c) LINE

highest y-value

bs

lowest x-value a]

si

100)-(4,

i

d

50)

There are two other graphics statements that are just as useful as the LINE statement. The statement PSET

(x, y)

plots the point with coordinates (x, y). The statement CIRCLES

(my)

aur

draws the circle with center (x, y) and radius r.

EXAMPLE

SOLUTION

3.

Write aprogram to plot the point (7, 6) and draw a circle of radius 3 about the point.

— The rightmost point to be drawn will have x-coordinate 10; therefore the numbers on the x-axis must range beyond 10. In the following program we allow the numbers to range from —2 to 12. (See Figure 10.5.) REM

Draw

SCREEN ‘For

circle

with

center

(7,

2 VGA

6)

and

radius

‘Initialize monitor

use

WINDOW (-2, -2)-(12, LINE (-2, 0)-(12, 0) LINE (0, -2)-(0, 12) PSET (7, 6) CIRCEER (7-06) es END

SCREEN

12)

12

in

line

3

screen

above

'Specify coordinate "Draw x-axis ‘Draw y-axis ‘Draw ‘Draw

system

center of circle the circle

SPECIFYING

10.2.

Figure 10.5

A COORDINATE SYSTEM

413

Graph for Example 3

The numbers appearing in WINDOW, LINE, PSET, and CIRCLE statements can be replaced by variables or expressions. For instance, the PSET statement in Example 3 can be replaced by Weise

BSI

= 7

(6%5

36 2710)

At any time, QBasic designates a point as the last point referenced. Initially, it is the point in the center of the screen. After a graphics statement is executed,

the point changes to a point appearing in the statement. After a PSET or CIRCLE statement is executed, the named point becomes the last point referenced. After a line is drawn, the second point named in the LINE statement becomes the last point referenced. A variation of the LINE statement uses the last point referenced. The statement LINE

-(x,

y)

draws a line from the last point referenced to the point (x, y) and makes (x, y)

the new last point referenced. Consider a statement of the form LINE (x1, yl)—(x2, y2) where one or both of the points (x1, yl) and (x2, y2) are off the screen. QBasic locates the points in a fictional coordinate system larger than the screen but containing the two

points. QBasic then "imagines" the line connecting the two points in the large coordinate system and displays only the portion of the line lying on the screen. That is, it clips off any hidden portion of the line. As before, (x2, y2) becomes the last point referenced. The following program produces the output of Figure 10.6. REM

Demonstrate

line

SCREEN 2 ‘For VGA monitor use WINDOW (0, 0)-(4, 2) LINE (0, 0)-(6, 2) LINE -(2, 0) END

clipping SCREEN

‘Last

12

pt.

and

last

point

in

line

above

ref.

referenced

is to right

of the

screen

414

Graphics

Figure 10.6

Line Clipping

Consider the task of drawing the line from (0, 0) to (2, 2). This line has

slope 1 and makes a 45 degree angle with the x-axis. Whether the line drawn by the statement LINE (0, 0)-(2, 2) makes a 45 degree angle with the x-axis depends on the WINDOW statement. Since the physical width and height of the screen are in a 4 to 3 ratio, true slopes are achieved with WINDOW statements for which b — a and d — c have a 4 to 3 ratio. Some

WINDOW

statements of this type are the following: WINDOW WINDOW WINDOW WINDOW

(-4, -3)-(4, 3) (-8, -6)-(8, 6) (-1, -1)-(7, 5) (0, 0)-(64, 48)

Comments:

1. In Examples 1 through 3, the range of numbers on the axes extended from a negative number to a positive number. Actually, any values of a, b, c, and dcan be used ina WINDOW statement. In certain cases, however, you will

not be able to display one or both of the axes on the screen. (For instance, after WINDOW

(1, —1)—(10, 10) has been executed, the y-axis cannot be

displayed.) 2. LOCATE statements are used to place text and therefore are not affected by WINDOW statements. 3. The radius of a circle uses the scale specified for the x-axis.

4. With a color VGA monitor, you can modify the above programs to produce colorful displays in very high resolution graphics mode. The numbers 0 through 15 identify colors as shown in Table 10.1.

O 1 2 3

Black Blue Green Cyan

Table 10.1

4 5 6 7

Red Magenta Yellow White

Values for Colors

8 9 10 11

Gray Light blue Light green Light cyan

12 13 14 15

Light red Light magenta Light Yellow High-intensity white

10.2

SPECIFYING

A COORDINATE SYSTEM

415

Lines, points, and circles can be drawn in colors. To use color c, place “, c” at the end of the corresponding graphics statement. For instance, the

statement LINE

(x1,

yl)-(x2,

y2),

4

draws a red line. 5. Appendix C describes the other QBasic graphics statements. (a) An extension of the CIRCLE statement draws ellipses, arcs, and sectors

of circles and ellipses. (b) The BLOAD statement restores the screen from a file created with BSAVE. (c) The BSAVE statement saves the contents of the graphics screen in a file. (d) The COLOR statement sets the background and drawing colors. (e) The DRAW statement creates sketches.

(f) The graphic GET and PUT statements create animation. (g) The PAINT statement fills in regions with colors or tiled patterns.

(h) The PALETTE and PALETTE USING statements specify a collection of colors to appear on the screen. (i) The PMAP function translates between natural and physical coordinates. (j) The PRESET statement erases points from the screen. (k) The SCREEN statement invokes many different graphics modes for EGA or VGA adapters. (1)

The VIEW statement translates, clips, or restricts graphics.

PRACTICE PROBLEMS

10.2

Suppose you want to write a program to draw the x- and y-axis and the line from (3,10) to (23,20).

1. Select a WINDOW statement so that the x- and y-axis can be drawn, the line fills most of the screen, and the line appears with the proper slope. 2. Write a program to draw the axes, the line, and a small circle around each

end point of the line.

3. Write the statements that draw a tick mark on the y-axis at height 10 and label it with the number 10.

EXERCISES

10.2

1. Determine the WINDOW tem of Figure 10.7.

statement corresponding to the coordinate sys-

416

Graphics

30

Figure 10.7 Exercise 1

Coordinate System for

2. Determine the WINDOW tem of Figure 10.8.

Figure 10.8 Exercise 2

Coordinate System for

statement corresponding to the coordinate sys-

3. Suppose that the statement WINDOW (-1, —8)—(4, 40) has been executed. Write down the statements that draw the x-axis and the y-axis. 4. Suppose that the statement WINDOW

(-3, — .2)—(18, 1) has been exe-

cuted. Write down the statements that draw the x-axis and the y-axis.

In Exercises 5 through 8, write a program to draw a line between the given points. Select an appropriate WINDOW statement, draw the axes, and draw a small circle around each end point of the line.

55 (3;200)5 (105150)

6. (4, 4), (9, 9)

Tipo

8. (30), (6,30)

Gee)

In Exercises 9 through 20, write a program to draw the given figures. Draw the axes only when necessary. 9. Draw a circle whose center is located at the center of the screen.

10. Draw a tick mark on the x-axis at a distance of 5 from the origin. 11. Draw a tick mark on the y-axis at a distance of 70 from the origin. 12. Draw a circle whose leftmost point is at the center of the screen. 13. Draw four points, one in each corner of the screen. 14. Draw a triangle with two sides of the same length. 15. Draw a rectangle. 16. Draw a square. 17. Draw five concentric circles, that is, five circles with the same center.

18. Draw a point in the center of the screen. 19. Draw a circle and a line that is tangent to the circle.

20. Draw two circles that touch at a single point.

10.3.

DRAWING GRAPHS OF FUNCTIONS

417

In Exercises 21 through 24, consider the following program. What would be the effect on the circle if the WINDOW WINDOW statement? SCREEN

statement were replaced by the given

2

WINDOW (-5, -5)-(5, CIRCEEN(O 0) 3

5)

‘Specify coordinate system ‘Draw circle centered at origin

END

21. WINDOW

(-8, —8) — (8,8)

22. WINDOW

23. WINDOW

(-8, —5) — (8, 5)

24. WINDOW (-2, -2) - (2, 2)

(—5, —8) — (5, 8)

25. Write a program to draw the graph of the line y = (1/2)x + 1. 26. Write a program to draw the graph of the line containing the two points (13) and (3,2).

27. Write a program to request the numbers r and s as input and then draw the graph of the straight line through the origin and point (r, s).

28. Write a program to request the values m and b as input and then draw the graph of the straight line y = mx + b.

SOLUTIONS TO PRACTICE PROBLEMS

10.2

1. To include the origin on the screen (and therefore the axes) and all of the line from (3,10) to (23,20), the smallest acceptable ranges for the x and y coordinates are 0 to 23 and 0 to 20. For

the slope to be correct, a 4 to 3 ratio between the overall range of the x and y coordinates is needed. If we let the x coordinates range from —4 to 28 and the y coordinates range from —2 to 22, then the minimum ranges are just met (so the line will fill as much of the screen as possible) and the ratio of the overall ranges is (28 — (-4))/(22 — (-2)) = 32/24 = 4/3. The WINDOW

statement to specify this coordinate system is WINDOW

(-4,

-2)-(28,

22)

2. The radius below for the small circles was chosen by trial and error. REM

draw

axes,

SCREEN

2

WINDOW

(-4,

a

line,

-2)-(28,

LINE LINE

(-10, 0)-(50, 0) (0, -5)-(0, 40)

LINE

(3,

10)-(23,

CIRCLE}

(e10)5.

Cuxcls

(35

20)5

and

endpoints

22)

20) 3 os

END

3. The LINE statement easily draws the tick mark at the precise height on the y-axis. Deciding where to LOCATE the cursor before PRINTing the 10 is a matter of trial and error. LINE

(-.5,

LOCATE 13, PRINT 10

10)-(.5, 6

10)

418

1 O

Graphics

3 DRAWING GRAPHS OF FUNCTIONS This section creates graphs of functions. Initially, the formula for a function is given explicitly. Then the function is given as the solution to a differential equation of the form y’ = g(t, y) with an initial condition.

Functions Given Explicitly EXAMPLE

SOLUTION

1

Write a program to draw the graph of the LOG function. See Figure 10.9.

— Of the many possible choices of a WINDOW statement, the one chosen here meets two criteria: the 4:3 ratio guarantees an accurate scale, and the graph fits nicely on the screen. The subprogram Initialize invokes a graphics mode, specifies the ranges of values for the x-axis and the y-axis, and draws the two axes. The subprogram Graph uses a FOR. ..NEXT loop to draw many points on the graph. The step size is set to 1/720 of the width of the screen since 720 is the largest number of pixels horizontally in any graphics mode. Since the LOG function is defined only for x > 0, plotting begins with a small positive value of x. REM Graph

the function

LOG(x)

DEF

FNf(x)

LET

a = -1:

LET

b = 7

"Extent

of

Wey

@ Sess

May

al ses}

‘Extent

of y-axis

=

LOG(x)

LET s = (b-

a) / 720

CALL Initialize(a, CALL Graph(.01, b, DO: LOOP END

b, s)

‘Step size c,

x = xl

PSET NEXT

(x,

x2

loop

'Supress

interval STEP s

"Press

[xl,

x2]

any

with

key

step

to

continue"

size

s

FNf(x))

x

END

SUB

SUB

Initialize

REM

TO

for FOR/NEXT

d)

SUB Graph (x1, x2, s) REM Draw graph over FOR

x-axis

Set

SCREEN

(a,

graphics

2

b,

c,

mode,

d) coordinate

scales,

draw

axes

"Invoke graphics mode and clear the screen "For VGA monitor use SCREEN 12 in line above WINDOW (a, c)-(b, d) LINE (a, 0)-(b, 0) ‘Draw x-axis LINE (0, c)-(0, d) "Draw y-axis END SUB

10.3.

Figure 10.9

DRAWING GRAPHS OF FUNCTIONS

A Graph of the Function f(x)

419

= LOG(x)

The program in Example | uses variables for the ranges of the x- and y-axes and passes the values of these variables to the subprograms. In practice, the programmer must experiment with different values of a, b, c, and d to obtain a good graph. The design of the program simplifies changing these values; only the third and fourth lines of the program need to be altered. The graph in Figure 10.9 can be improved by graphing with line segments instead of points. The revision of the subprogram below produces the graph shown in Figure 10.10. This figure contains all the points of Figure 10.9, but uses the last point referenced to connect these points with line segments. SUB Graph (xl, x2, s) REM Draw graph over PSET

(xl,

FOR

x = xl

LINE NEXT END

-(x,

interval

[xl,

x2]

with

STEP

s

FNf(x1)) TO

x2

STEP

s

FNf(x))

x

SUB

Figuré 10.10

An Improved Graph of the Function f(x)

= LOG(x)

420

Graphics

Although the “4:3 ratio rule” produces an accurately scaled graph, the rule is not appropriate for certain functions. For instance, a reasonable coordinate system for the graph of f(x) = x’ from x = -10 to x = 10 is specified by the statement WINDOW

(-10,

-1000)-(10,

1000)

which is far from a 4:3 ratio. Since the graph of the LOG function has a vertical asymptote at x = 0 and is not defined for negative values of x, the function was evaluated only to the right of its asymptote. Often there are points on both sides of a vertical asymptote. Also, vertical asymptotes are typically drawn as dashed lines. To draw a dashed line, use the LINE statement in one of the following modified forms: LINE

(@,

Imes,

LINE

=(a,

b)?

Gis. 5

5 4 So

5 3855

2

See Figure 10.11.

EXAMPLE 2

Write a program to draw the graph of f(x) = 5 + ae (x—1)(x-2)

SOLUTION

The objective is to have the graph exhibit the key features of the function. Since the function has vertical asymptotes at x = 1 and x = 2, it has three pieces: the piece to the left of 1, the piece between | and 2, and the piece to the right of 2. These three pieces are each graphed by a separate call to the subprogram Graph. Evaluating the function at x = 1 and x = 2 produces a “Division by zero” error message. In addition, evaluating the function at a value of x very close to 1 or 2 might result in a number so large that an Overflow error message is generated. Therefore, the program stays s units from 1 and 2. (In extreme cases, a distance

of 2*s or more may be required.) Experimentation was used to obtain the arguments for the WINDOW statement. REM Graph a function with asymptotes DERSEN T(x) > 2. Set alOesixeo ha) (Xero) UENea0=5-9< LET be=—5 "Extent LET c = -200: LET d = 200 "Extent

PEqest=y(b CALL CALL CALL CALL CALL CALL DO:

0a)

7720

eke (Knee), of x-axis of y-axis

"Step size

Initialize(a, b, c, d) Graph(a, 1 - s, s) VerticalAsymptote(1, c, Graph(1 + s, 2 - s, s) VerticalAsymptote(2, c, Graph(2 + s, b, s) LOOP

"Draw

in FOR/NEXT

the

piece

from

-3 to

‘Draw the

piece

from

1 to 2

‘Draw the "Suppress

piece from "Press any

FORT

X= = x19

LINE NEXT END

SUB

x

-(x,

interval

10=xZ2eSiERSs

FNf(x))

l

d)

d)

END

SUB Graph (xl, x2, s) REM Draw graph over Ee (oak, aa}

loop

[xl,

x2]

with

STEP

s

2 to 5 key to continue"

10.3.

SUB

Initialize

REM

Set

(a,

graphics

b,

c,

mode,

DRAWING GRAPHS OF FUNCTIONS

d) coordinate

SCREEN 2 "For WINDOW (a, c)-(b, d) LINE (a, 0)-(b, 0) ‘Draw x-axis LINE (0, c)-(0, d) ‘Draw y-axis END SUB

SUB VerticalAsymptote REM

Draw

LIME (es END SUB

the

vertical

Glee,

Figure 10.11

(r,

yh

421

c, dashed

scales,

draw

VGA

SCREEN

use

axes

12

d) line

x = r

5 5 SE05

10x”

Graph of f(x) = 5 + (x -1)(x-2)

Euler’s Method for Graphing the Solution to a Differential Equation Consider a differential equation of the form y =g(t,y), ,

to “ape”) OR (“earth’>“moon”) is true since “apple”>“ape” is true, while (1>2) OR (“moon”2) and (“moon’“ape”) XOR (“earth”>“moon”) is true since “apple” >“ape” is true and “earth”>“moon” is false. XOR (Bitwise Operator) The expression byte! XOR byte2 is evaluated by expressing each byte as an 8-tuple binary number and then XORing together corresponding digits, where 1 XOR O and 0 XOR 1 both equal 1, while 1 XOR 1 andO XOR 0 both equal 0. For example, the expression 37 XOR 157 translated to binary 8-tuples becomes 00100101 XOR 10011101. XORing together corresponding digits gives the binary 8-tuple 10111000 or decimal 184. Thus 37 XOR 157 is 184.

Supporting Topics [1] Default values. Before a numeric, variable-length string, or fixed-length string variable of length n has been assigned a value by the program, its value is O, the null string (“”), or a string of n CHR$(0) characters respectively. [2] Radian measure.

The radian system of measurement measures angles in

terms of a distance around the circumference of the circle of radius 1. If the vertex of an angle between 0 and 360 degrees is placed at the center of the circle, then the length of the arc of the circle contained between the two sides of the angle is the radian measure of the angle. An angle of d degrees has a radian measure of (J/180)*d radians. [3] Directories.

Think of a disk as a master folder holding other folders, each

of which might hold yet other folders. Each folder, other than the master folder, has a name. Each folder is identified by a path: a string beginning with a drive letter, a colon, and a backslash character, ending with the name of the folder to be identified, and listing the names of the intermediate folders (in order)

separated by backslashes. For instance the path “C:\DAVID\GAMES” identi-

fies the folder GAMES which is contained in the folder DAVID, which in turn is contained in the master folder of drive C. Each folder is called a directory and the master folder is called the root directory. When a folder is opened, the revealed folders are referred to as its subdirectories. Think of a file as a piece of paper inside one of the folders. Thus,

each directory contains files and subdirectories.

Appendix C — QBasic Statements

547

At any time, one of the directories is said to be the current directory. Initially the root directory is the current directory. The current directory can be changed from DOS with the CD command or from QBasic with the CHDIR command. DOS and QBasic statements that access files, such as DIR and FILES, act on the

files in the current directory unless otherwise directed.

The default drive is the drive whose letter appeared in the DOS prompt when QBasic was invoked. If a drive is missing from a path, then the drive is assumed to be the default drive. [4] Filespec.

The filespec of a file on disk is a string consisting of the letter of

the drive, a colon, and the name of the file. If directories are being used, then

the file name is preceded by the identifying path. [5] Colors. Sixteen predefined colors, identified by the numbers 0 through 15, are available on color monitors: O 1 2 3

Black Blue Green Cyan

4 5 6 7

Red 8 Gray Magenta 9 Light Blue Brown 10 Light Green White 11 Light Cyan

12 13 14 15

Light Red Light Magenta Yellow Intense White

In text mode, which is invoked with the statement SCREEN

0, any of the

colors are available as foreground colors and the first eight are also available as background colors. In medium resolution graphics mode, which is invoked with the statement SCREEN 1, two palettes of four colors each are available. Palette 0:

0. Background color

1. Green

2. Red

3. Brown

Palette 1:

0. Background color

1. Cyan

2.Magenta

3. White

In high resolution graphics mode, invoked with the statement SCREEN 2, only two colors, black (0) and white (1) are available. See the discussion of

SCREEN for the ranges of colors available in the higher graphics modes. [6] Palettes.

A palette can be thought of as a collection of numbered jars that

can hold paint. The number of jars available varies with the screen mode. Although the jars hold specified default colors, EGA, MCGA, and VGA adapters allow the colors to be changed with the PALETTE statement. Statements of the form PSET (x,y),c and CIRCLE (x,y),r,c use the color in the cth

paint jar. In the absence of aCOLOR statement, the PRINT statement displays characters with the color in jar 0 as the background color and the color in the highest numbered jar as the foreground color. [7] Last point referenced. At any time, one point on the screen is designated as the “last point referenced.” Initially it is the point in the center of the graphics screen. After a graphics statement is executed, the point changes to one of the points used in the statement. For instance, after a circle is drawn, the center of the circle becomes the last point referenced. After a line is drawn, the right point named in the LINE statement becomes the last point referenced. [8] Graphics coordinate systems. The standard graphics coordinate system is called the physical coordinate system. For the high resolution screen mode (SCREEN 2), the y-coordinates range from 0 to 199 moving from the top to the bottom of the screen, and the x-coordinates range from 0 to 639, moving from the left to the right side of the screen. See the discussion of SCREEN for the

548

Appendix

C — QBasic Statements

ranges in the higher graphics screen modes. The WINDOW statement can be used to specify a different coordinate system, called a natural or logical coordinate system. Points can also be specified in terms of relative coordinates. The phrase STEP (x,y) refers to the point obtained by starting at the last point referenced and moving x units in the horizontal direction and y units in the vertical direction. Relative coordinates can be used in all statements that produce graphics. [9] Memory.

Each memory location holds an integer from 0 to 255. This unit

of data or memory is called a byte. The computer’s memory is divided into blocks of memory locations called segments. Each segment is 65,536 bytes in size. Within a segment, a particular memory location can be specified by giving its offset (a number from 0 to 65,535) from the beginning of the segment. Thus, to locate an item in memory, both its segment and offset within that segment must be known, although in many cases just the offset is sufficient. Segments overlap, that is, the same portion of memory may be considered to be within different segments. Segment 0 extends from location 0 to location 65535. Segment 1 extends from location 16 to location 65551. Segment 2 extends from location 32 to 65567, and so on. For instance, the 34th memory location can be identified

as segment 0: offset 34, segment 1: offset 18, or segment 2: offset 2. QBasic reserves a special segment, called the Default Data Segment or DGROUP, where it stores variables, special values such as the current row and column of the cursor, and the value of the random seed. The current segment of memory is used in conjunction with the offsets given in BLOAD, BSAVE, PEEK, and POKE statements. At the start of program execution, the current segment of memory is the Default Data Segment. It can be changed at any time by the DEF SEG statement. [10] Device.

Some examples of devices are the video screen, keyboard, printer,

modem, and diskette drives. The computer’s microprocessor receives data from and sends data to the various devices of the computer through what are called ports. Each port is identified by a number from 0 to 65535. A byte of data consists of a number from 0 to 255.

[11] Random-access files. The two methods for writing records to and reading records from random-access files are the “record variable method” and the “buffer method.” The record variable method is discussed in Chapter 9. With the buffer method, a portion of memory referred to as a buffer is set aside for the file. A FIELD statement specifies fixed-length string field variables whose values are held in the buffer. LSET and RSET statements assign values to the field variables, and PUT and GET statements move the contents of the buffer into a record of the file, and vice versa, respectively. The functions MKI$, MKL$, MKS$, and MKD$ are used to convert numbers to fixed-length strings prior to being placed into the buffer by LSET and RSET statements. After a GET statement places a record in the buffer, the functions CVI, CVL, CVS, and CVD are used to convert

the these strings back into numbers of the appropriate type. [12] Binary file. A file that has been opened with a statement of the form OPEN “filespec” FOR BINARY AS #n is regarded simply as a sequence of characters occupying positions 1, 2, 3,.... At any time, a specific location in

the file is designated as the “current position.” The SEEK statement can be is used to set the current position. Collections of consecutive characters are written

Appendix

C — QBasic Statements

549

to and read from the file beginning at the current position with PUT and GET statements, respectively. Aftera PUT or GET statement is executed, the position following the last position accessed becomes the new current position.

[13] Label. QBasic supports two mechanisms for identifying program lines that are the destinations of statements such as GOTO and GOSUB: line numbers and descriptive labels. Descriptive labels are named using the same rules as variables, and are followed by a colon. When a label appears in a GOTO or GOSUB statement, execution jumps to the statement following the line containing the label. We use the word label to refer to either a descriptive label or a line number. [14] Subroutines. A subroutine is a sequence of statements beginning with a label and ending with a RETURN statement. A subroutine is meant to be branched to by a GOSUB statement and is usually placed so that it cannot be entered inadvertently. For instance, in the main body of a program, subroutines might appear after an END statement.

[15] Event trapping. Special events, such as the pressing of a function key or the occurrence of an error, can be set to trigger a jump to a subroutine. These events are specified by statements of the general form Event ON and ON Event GOSUB label that cause the computer to check for the event after the execution of each statement. If the event has occurred, the computer then performs a GOSUB to the subroutine at label. Trapping is disabled with Event OFF and deferred with Event STOP. [16] Metacommand.

The statements $STATIC, and $DYNAMIC

are called

metacommands. Metacommands instruct the interpreter to insert certain code into the program

or to treat certain QBasic

statements

in a particular way.

Because metacommands are not executed, they are preceded by the reserved word REM (or an apostrophe). For instance, the statement REM $STATIC or ’$STATIC tells the interpreter to store arrays in a special way. [17] Static vs. dynamic. QBasic uses two methods of storing arrays, dynamic and static. The memory locations for a static array are set aside at compile time and this portion of memory may not be freed for any other purpose. The memory locations for a dynamic arrai are assigned at run-time and can be freed for other purposes. Although dynamic arrays are more flexible, static arrays can be accessed faster. QBasic uses the dynamic allocation of arrays if either the range in a DIM statement is specified by a variable or the programmer insists on dynamic allocation with a $DYNAMIC metacommand.

Appendix D

OBasic Debugging Tools Bee in programs are called bugs and the process of finding and correcting them is called debugging. Since the QBasic interpreter does not discover errors due to faulty logic, they present the most difficulties in debugging. One method of discovering a logical error is by desk-checking, that is, tracing the values of variables on paper by writing down their expected value after “mentally executing” each line in the program. Desk checking is rudimentary and highly impractical except for small programs. Another method of debugging involves placing PRINT statements at strategic points in the program and displaying the values of selected variables or expressions until the error is detected. After correcting the error, the PRINT statements are removed. For many programming environments, desk checking and PRINT statements are the only debugging methods available to the programmer. The QBasic debugger, used in conjunction with the Immediate window, offers an alternative to desk checking and PRINT statements. The debugging tools are invoked from the Debug menu.

Using the Immediate Window The F6 key moves the cursor back and forth between the Immediate window and the View window. The Immediate window can hold several lines of QBasic statements. When the cursor is placed on one of these lines and the Enter key is pressed, the line is executed immediately. The following walkthrough uses the Immediate window to display and alter the values of variables. 1. Notice that the title bar, centered above the View window, is highlighted.

2. Press the function key F6 to activate the Immediate window. Notice that the bar containing the word “Immediate” is highlighted and the cursor is located in the Immediate window.

3. Press F6 to reactivate the View window. The title bar is now highlighted and the cursor is in the View window.

4. Press Alt/F/N to clear any previous program from memory and then type the following program into the View window. Do not run this program yet. CIES LET x = 1 LET y= 2 PRINT

END

550

x + y

Appendix D — QBasic Debugging Tools

551

5. Activate the Immediate window and type the line PRINT

[X=os °xXp

yes

y,

x >-y

into the Immediate window.

6. With the cursor on the line, press the Enter key. The values of the variables x and y and the condition x > y, all zero, will be displayed in the output window. The value of a condition is displayed as —1 if the condition is true and 0 if the condition is false. 7. Press any key to return to the Immediate window. 8. Activate the View window and run the program.

9. Activate the Immediate window, move the cursor to the line typed in 5, and press the Enter key. The new values of the variables and the value of the condition will be displayed on the Output screen. 10. Press any key to return to the Immediate window. 11. On a new line in the Immediate window, type the statement EET

©x7=

100

12. Press the Enter key with the cursor on this new line. The Output screen reappears, but is unchanged, since no new items have been displayed. 13. Press any key to return to the Immediate window, move the cursor to the PRINT statement, and press the Enter key. The values of x, y, and the condition x > y are displayed, with new values for x and the condition. Since x > y is now true, its value appears as —1.

Using the QBasic Debugger The two main features of the QBasic debugger are stepping and breakpoints. The program can be executed one statement at a time, with each press of an appropriate function key executing a statement. This process is called stepping. After each step, values of variables, expressions, and conditions can be displayed from the Immediate window, and the values of variables can be changed. When a procedure is called, the lines of the procedure can be executed one at a time, referred to as “stepping through the procedure,” or the entire procedure can be executed at once, referred to as “stepping over a procedure.” A step over a procedure is called a procedure step. Normally, stepping begins with the first statement of the program, and proceeds to execute the statements in order. However, at any time the programmer can specify the next statement to be executed. As another debugging tool, QBasic allows the programmer to specify certain lines as breakpoints. Then, when the program is run, execution will stop at the first breakpoint reached. The programmer can then either step through the program or continue execution to the next breakpoint. The tasks discussed above are summarized below, along with a means to carry out each task. The tasks invoked with function keys can also be produced from the menu bar.

552

Appendix D— QBasic Debugging Tools

Press F8

Step (ordinary):

Procedure step: Press F10 Set a breakpoint:

Move cursor to line, press F9

Remove a breakpoint:

Move cursor to line containing breakpoint, press F9

Clear all breakpoints:

Press Alt/D/C

Set next statement:

Press Alt/D/N

Execute program to the line containing the cursor: Press F7 Continue execution to next breakpoint or the end of the program: Toggle between View window and Output screen:

Press F5

Press F4

Six Walkthroughs The following walkthroughs use the debugging tools with the programming structures covered in Chapters 3, 4, 5, and 6.

Stepping Through an Elementary Program: Chapter 3 The following walkthrough demonstrates several capabilities of the debugger.

1. Type the following program into the View window. cls INPUT

"Enter

a number:

LET

num

= num

+

LET

num

= num

+ 2

PRINT

",

num

1

num

END

2. Press F8. The CLS statement is highlighted to indicate that it is the next statement to be executed. 3. Press F8. The CLS statement is executed and the INPUT statement is highlighted to indicate that it is the next statement to be executed. To confirm that CLS really was executed, press F4 to see the blank Output screen. (Press F4 again to return to the View window.)

4. Press F8 to execute the INPUT statement and respond to the request by entering 5. 5. Press F8 four more times to execute the rest of the program.

6. Move the cursor to the line LET num = num + 2. Press F9 to highlight the line and set it as a breakpoint. (Pressing F9 has the same consequence as invoking the “Toggle Breakpoint” option from the Debug menu by pressing Alt/D/B.) 7. Press Shift+F5. The program executes the first three lines and stops at the breakpoint. The breakpoint line is not executed. (Again, respond to the INPUT statement with 5.)

Appendix D — QBasic Debugging Tools

553

8. Type the statement PRINT

"num

=";

num

into the Immediate window and then press Enter to execute the statement. The appearance of num = 6 in the Output window confirms that the breakpoint line was not executed. 9. Press any key and then F6 to return to the View window.

10. Move the cursor to the line LET num = num + 1 and then press Alt/D/N to specify that line as the next line to be executed. 11. Press F8 to execute the selected line.

12. Use the Immediate window to confirm that the value of num is now 7, and then return to the View window.

13. Move the cursor to the breakpoint line and press F9 to deselect the line as a breakpoint.

14. Press F5 to execute the remaining lines of the program. The value displayed 1s 9.

Stepping Through Programs Containing Selection Structures: Chapter 4 IF Blocks The following walkthrough demonstrates how an IF statement evaluates a condition to determine whether to take an action. 1. Type the following program into the View window. CES INPUT

wage

IF wage < 4.25 THEN PRINT "Below minimum EUSE PRINT "Wage Ok." END IF END

wage."

2. Press F8 twice. The CLS statement will be highlighted and executed, and then the INPUT statement will be highlighted.

3. Press F8 once to execute the INPUT statement. Type a wage of 3.25 and press the Enter key. The IF statement is highlighted, but has not been executed. 4. Press F8 once and notice that the highlight for the current statement has jumped to the statement PRINT “Below minimum wage.” Since the condition “wage < 4.25” is true, the action associated with THEN was selected.

554

Appendix

D— QBasic Debugging Tools

5. Press F8 to execute the PRINT statement. Notice that ELSE, the statement

immediately following the PRINT statement, is highlighted.

the h wit h oug thr are we ed, ass byp is ion act E ELS the ce Sin n. agai 6. Press F8 IF block and the statement following the IF block, END, is highlighted. 7. Press F8 once more to complete execution of the program.

8. If desired, try stepping through the program again with 5.75 entered as the wage. Since the condition “wage < 4.25” will be false, the ELSE action will be executed instead of the THEN

action.

SELECT CASE Blocks the uses k bloc E CAS ECT SEL a how tes stra illu gh rou kth wal g owin foll The selector to choose from among several actions. 1. Type the following program into the View window. GES INPUT age SELECT CASE age CASE US e= 65 LET price = 4 CASE ELSE LET price = 5.5 END SELECT PRINT USING "Your ticket END

price

is

$#.##";

price

2. Press F8 twice. The CLS statement will be highlighted and executed, and then the INPUT statement will be highlighted. 3. Press F8 once to execute the INPUT statement. Type an age of 8 and press the Enter key. The SELECT CASE statement is highlighted, but has not been executed. 4. Press F8 once and observe that the action associated with CASE IS < 12 is

highlighted. 5. Press F8 once to execute the LET statement. Notice that the clause following the LET statement, “CASE IS < 18,” is highlighted. 6. Press F8 once. Observe that although the selector, age, is less than 18, the

action associated with that CASE clause was ignored and the highlight jumped outside the SELECT CASE block to the PRINT USING statement. This demonstrates that when more than one CASE clause is true, only the first is acted upon. 7. Press F8 twice to complete execution of the program.

8. If desired, step through the program again, entering a different age and predicting which CASE clause will be acted upon.

Appendix D — QBasic Debugging Tools

555

Stepping Through a Program Containing a DO Loop: Chapter 5 DO Loops

The following walkthrough demonstrates use of the Immediate window to monitor the value of a condition in a DO loop that searches for a name. 1. Enter the following program into the View window. REM Look for a specific name CLS INPUT "Name"; searchName$ 'Name to search for READ name$ DO WHILE (searchName$ name$) AND (name$ READ name$ LOOP PRINT name$ ‘Print found name or EOD REM

DATA

---

Data:

Bert,

in

list

"EOD")

name

Ernie,

Grover,

Oscar,

EOD

END

2. Press F6 to activate the Immediate window.

3. Type, but do not press the Enter key, PRINT

searchName$,

name$,

(searchName$

name$)

AND

(name$

"EOD")

4. Press F8 three times to execute CLS and the INPUT statement. Enter the

name “Grover” at the prompt. 5. Press F8 once to execute the READ statement.

6. Press F6 to activate the Immediate window, move the cursor to the PRINT

statement, and press the Enter key. The variable name$ has been assigned the first item in the DATA statement, “Bert”, and the value of the WHILE

condition is displayed as —1. (True conditions are displayed as —1; false conditions are displayed as 0.) Since the two conditions (searchName$ name$) and (name$ “EOD”) are both true, the compound condition is

true. (Press any key to continue.)

7. Press F8 once. Since the WHILE condition is true, the DO loop is entered. 8. Press F8 once to READ the next DATA item. 9. Execute the statement in the Immediate window. The value of name$ is now

“Ernie.” (Press any key to continue.) Although the highlight is on the word LOOP, QBasic is really preparing to evaluate the WHILE condition to see if the loop should be executed again. 10. Press F8. Since the WHILE condition is true, the statement inside the loop

is highlighted. 11. Press F8 to READ the next item from the DATA statement.

12. Execute the statement in the Immediate window. Since searchName$ and name$ have the value “Grover”, the condition (searchName$ name$)

is false. Hence the entire WHILE condition is false, and is displayed with the value 0.

556

Appendix

D— QBasic Debugging Tools

t ligh high the , false ome bec has ion dit con LE WHI the e Sinc . once F8 s 13. Pres will move from the LOOP statement to the statement immediately following the DO loop, that is, PRINT name$.

14. Press F8. The value displayed on the screen by PRINT is the same as the value of name$ most recently displayed from the Immediate window. (Press F4 to view the Output screen.) 15. Press F8 once to complete execution of the program.

Stepping Through a Program Containing a Procedure: Chapter 6 The following walkthrough uses the single-stepping feature of the debugger to trace the flow through a program and a subprogram CALL. 1. Type the following program into the View window. CLS LET p = 1000 ‘Principal CALL GetBalance(p, b) PRINT "The balance is";

b

END

SUB GetBalance (prin, bal) REM Calculate the balance LET interest = .05 * prin LET bal = prin + interest END SUB

at

5%

interest

rate

2. Press F8. The CLS statement is highlighted to indicate that it is the next statement to be executed. 3. Press F8 two more times. The CALL statement is highlighted. 4. Press F8 once and observe that the subprogram GetBalance is now displayed on the screen with its first executable statement highlighted. (The subprogram heading and REM statement have been skipped.) 5. Press F8 twice to execute the LET statements and to highlight the END SUB statement. 6. Press F8 and notice that the main body is again displayed in the View window with the highlight on the statement immediately following the CALL statement. 7. Press F8 twice to execute the PRINT statement and the END statement.

Communication Between Arguments and Parameters

The following walkthrough uses the Immediate window to monitor the values of arguments and parameters during the execution of a program.

1. If you have not already done so, type the preceding program into the View window.

Appendix D — QBasic Debugging Tools

557

2. Press F6 to activate the Immediate window. Type in, but do not execute, the following two lines. (Use the Home key and cursor-down key to move to the beginning of a new line instead of pressing the Enter key.) PRINT

to)

PRINT

"prin

=.

Ds

"b

="5

=" 3 prin,

b

"bal

="3

bal

3. Press F8 three times to highlight the CALL statement. 4. Activate the Immediate window, place the cursor on the first PRINT statement created in step 2, and press the Enter key to display the values of p and b. 5. Press any key, and then Press F8 to call the subprogram.

6. Activate the Immediate window, place the cursor on the second PRINT statement created in step 2, and press the Enter key to display the values of prin and bal. The variables prin and bal have inherited the values of p and

b. 7. Press any key, and then press F8 twice to execute the subprogram.

8. Activate the Immediate window and display the values of prin and bal. 9. Press any key, and then press F8 to return to the main body of the program.

10. Activate the Immediate window and display the values of p and b. The variable b now has the same value as the variable bal.

11. Press F8 twice to complete execution of the program.

12. Activate the Immediate window and display the values of prin and bal. These variables both have value 0 since they are not recognized by the main body of the program.

Appendix E

A Summary of QBasic Editing Commands he charts below summarize the editing commands presented in Chapter 1. These charts are followed by some advanced editing commands that use QBasic’s Clipboard. Commands

to Move Cursor

Left one character Right one character Left to start of word Right to start of word Left to start of line Right to end of line Up one line Down one line Up to first line in program Down to last line in program

Left Arrow Right Arrow Ctrl+Left Arrow Ctrl+Right Arrow Home End Up Arrow Down Arrow Ctrl+Home Ctrl+End

Commands to Scroll Up to Down Scroll Scroll

a new page to a new page view up one line in program view down one line in program

Commands

PgUp PeDn Ctrl+Up Arrow Ctrl+Down Arrow

to Delete Text

Delete character left of cursor Delete character at cursor Delete from cursor to end of word

Backspace Del Ctrl+T

Delete from cursor to end of line Delete entire line

Shift+End/Del Ctrl+Y

Using the Clipboard QBasic sets aside a part of memory, called the Clipboard, to assist in moving and copying selected portions of text. Whenever text is deleted with one of the commands Ctrl+T (erase word) or Ctrl+Y (erase current line) the text is placed

in the Clipboard. At any time, pressing Shift+Ins inserts the contents of the Clipboard at the cursor position. The following steps can be used to move a line of code to a new location. 1. Place the cursor on the line.

2. Press Ctrl+Y to erase the line and place it into the Clipboard. 558

Appendix E — A Summary of QBasic Editing Commands

559

3. Move the cursor to the desired new location for the line.

4. Press Shift+Ins to duplicate the line at the cursor position.

Note: After the contents of the Clipboard are copied text remains in the Clipboard and therefore can locations. Larger portions of contiguous text, called blocks, Clipboard. To select a segment of text as a block,

at the cursor position, the be duplicated in several

also can be stored in the move the cursor to the beginning of the segment, hold down the shift key, move the cursor to the end of the segment of text, and then release the shift key. The selected block will be highlighted. (Moving the cursor deselects the portion of text as a block.) After highlighting a block, the following commands can be applied to the selected block.

Shift+Del

— Erases the selected block and places it in the Clipboard

Ctrl+Ins

Places a copy of the selected block in the Clipboard while leaving the block intact

Del

Erases the selected block without placing it in the Clipboard

After placing a block of text into the Clipboard, the following steps can be used to copy the contents of the Clipboard anywhere in a program. 1. Move the cursor to the location where the block stored in the Clipboard should be inserted. 2. Press Shift+Ins to insert the block at the cursor position.

Appendix F

The QBasic Environment his appendix discusses the eight Menu bar selections and their pull-down menus. The File Menu Commands Pressing F from the Menu bar (or Alt/F from the View or Immediate window)

pulls down the File menu, presenting the following six command options. New

The New command clears any current program from the editor’s memory, allowing a new program to be written. The new program is given the default name of Untitled.BAS. If the New command is given when a recently edited program is in memory, QBasic provides an opportunity to save this edited program before the editor’s memory is loaded with the new program. Open

The Open command copies a program from a disk into the View window so that the program can be edited or run. If the Open command is given when a recently edited program is in memory, QBasic provides an opportunity to save this edited program before the editor’s memory is loaded with the new program.

The Open command exhibits a box with the cursor in a rectangle entitled “File Name.” To load a file, type the filename (including the drive and path if warranted) into the rectangle and press the Enter key. If the file name has the standard extension of BAS, you need not include the extension. (To specify a file whose name has no extension, include the period at the end of the file name.) If the file you request is not present, QBasic assumes you want to start working on a new program that will later be saved in a file with this new name. An alternate way of loading a file is provided by the Files rectangle which displays the names of all the files with extension BAS in the current directory of the current drive. A program can be loaded by pressing the Tab key, moving to the desired name with the cursor-moving keys, and pressing the Enter key. The drive can be changed by making a selection from the Dir/Drives rectangle. The drive and/or directory of the programs displayed in the Files rectangle can be changed by typing and entering the identifying path in the File Name rectangle. Wild card characters, the asterisk and question mark, can be used to request a class of file names from the directory. A question mark in a file name indicates that any character can occupy that position. An asterisk in either part of the file name, the first eight positions or the extension, indicates that any

character can occupy that position and all the remaining positions in the part.

560

Appendix

F — The QBasic Environment

561

For instance, typing and entering A: \TOM \?R*.BAS displays all files on the A drive in the directory TOM having R as the second letter and having the extension BAS. Save

The Save command copies the program currently in memory onto a disk. If the program has not been named (that is, if its current name appears as Untitled in the Title bar), QBasic exhibits an input box titled File Name that provides the

opportunity to give the file a meaningful name. If the file name ends with a period, then it will be saved with no extension. Otherwise, if the file name has

no extension, the extension BAS will automatically be added. The file is saved in the current directory of the current drive unless its name is preceded with a drive and/or path. The drive also can be selected from the Dir/Files rectangle. Save As

The Save As command copies the program currently in memory onto a disk after providing an opportunity to save the program under a name other than the current name. The dialog box is identical to the one for Save. Print

The Print command prints a hard copy of the part of the program that has been selected as a block, the current window (that is, the View window, the Immediate

window, or a procedure), or the entire program, depending on which option is selected.

Exit The Exit command abandons QBasic and returns to DOS. If the Exit command is given when the program in the View window has not been saved in its current form, the user is given the opportunity to save before QBasic is abandoned. The Edit Menu Commands Pressing E from the Menu bar (or Alt/E from the View or Immediate windows)

pulls down the Edit menu, presenting the following six command options. Cut

The Cut command removes the selected block of text from the View window

and places it in the clipboard. Copy

The Copy command places a copy of the selected block of text into the clipboard. The copied text will still be in the View window. Paste

The paste command inserts, at the cursor, a copy of the contents of the clipboard.

562

Appendix

F — The QBasic Environment

Clear

The Clear command removes the selected text without saving it in the clipboard. (Clipboard contents remain unaltered.) New SUB

The New SUB command opens a dialog box in which the programmer enters the name of anew subprogram. After pressing the Enter key, the new subprogram

will be created and the cursor will appear below the heading. New FUNCTION The New FUNCTION command opens a dialog box in which the programmer enters the name of a new function. After pressing the Enter key, the new function will be created and the cursor will appear below the heading. The View Menu Commands Pressing V from the Menu bar (or Alt/V from the View or Immediate window)

pulls down the View menu, presenting the following three command options. SUBs

The SUBs command displays a dialog box used to select a procedure to view or delete. Split

The Split command divides the View window horizontally so two parts of a program can be accessed at the same time. The F6 and Shift+F6 keys move between the windows. The size of the active window can be expanded one line at a time with Alt+Plus and shrunk with Alt+Minus. Ctrl+F10 toggles between an expanded View window and its regular size. Output Screen

The Output Screen command toggles to and from the display of the output screen. The same function is performed by the F4 key. The Search Menu Commands Pressing S from the Menu bar (or Alt/S from the View or Immediate window)

pulls down the Search menu, presenting the following three command options.

Find The Find command begins at the cursor and searches for the first occurrence of a specified symbol, word, or phrase.

Repeat Last Find

The Repeat Last Find command looks for the next occurrence of the text most recently searched for by the Find command.

Appendix F — The QBasic Environment

563

Change

The Change command begins at the cursor, finds the first occurrence of specified text, and replaces it with new text. The Run Menu Commands Pressing R from the Menu bar (or Alt/R from the View or Immediate windows) pulls down the Run menu, presenting the following three command options.

Start

The Start command executes the program currently in memory, beginning with the first line. Pressing Shift+F5 performs the same function. Restart When a program has been suspended before completion, the Restart command specifies that the next call for execution of the program should restart the program from the beginning. Continue

When a program has been suspended before completion, the Continue command resumes execution at the suspension point. The same function is performed by the F5 key.

The Debug Menu Commands Pressing D from the Menu bar (or Alt/D from the View or Immediate windows) pulls down the Debug menu, presenting the following six command options. Step

The Step command executes the program one statement invocation of the command executes the next statement.

at a time. Each

Procedure Step

The Procedure Step command executes the program one statement at a time without stepping through the statements inside procedures one at a time. An entire procedure is executed as if it were a single statement. Trace On

The Trace On line shows the current status of the Trace toggle. When Trace On is preceded by a dot, each statement will be highlighted as it is executed. This feature lets you observe the general flow of the program.

Toggle Breakpoint

A breakpoint is a line of the program at which program execution is automatically suspended by QBasic. The Toggle Breakpoint command toggles (that is, sets or clears) the line containing the cursor as a breakpoint.

564

Appendix F — The QBasic Environment

Clear All Breakpoints

The Clear All Breakpoints commands removes all breakpoints that have been set with the toggle breakpoint command. Set Next Statement

The Set Next Statement specifies that the line containing the cursor be the next line executed when program execution continues.

The Options Menu Commands Pressing O from

the Main

Menu

(or Alt/O from

the View

or Immediate

windows) pulls down the Options command menu, presenting the following three command options.

Display The Display command generates a dialog the foreground and background of text statements highlighted during debugging, by a mouse, and to specify the number of

box that can be used to custom-color typed into the View windows and to select or deselect the scroll bars used spaces tabbed by the Tab key.

Help Path

The Help Path command is used to tell QBasic where to look for the file QBasic.HLP, the file containing the Help information. Normally, the file is in the same directory as QBasic.EXE. If not, the path specifying the directory containing QBasic.HLP should be entered in the rectangle invoked by the Help Path command. A complete path consists of a disk drive followed by a sequence of subdirectories.

Syntax Checking Normally, checks the to improve ceded with

when a line of text is Entered, QBasic’s smart editor automatically correctness of the line, capitalizes key words, and adds extra spaces readability. This feature is enabled when Syntax Checking is prea dot. The Syntax Checking command toggles this state.

The Help Menu Commands Pressing H from the Menu bar (or Alt/H from the View or Immediate windows)

pulls down the File menu, presenting the following five command options.

Index The Index command displays an alphabetical list of keywords. Information on a keyword can be obtained by placing the cursor on the keyword and pressing the Enter key or F1. Pressing a letter key moves the cursor to the first keyword beginning with that letter.

Appendix

F — The QBasic Environment

565

Contents

The Contents command displays a menu of topics on which information is available. After the Tab or direction keys are used to move the cursor to a topic,

pressing Enter or F1 displays the information. Topic

When the cursor is located at a keyword in the View window, you can invoke the Topic command to obtain information about that word. Using Help

The Using Help command displays information about how to obtain online help. About

The About command displays the version number and copyright dates of the QBasic currently in use.

Appendix G

How To (QBasic) HOW

TO: Invoke and Exit QBasic

(We assume that the computer has a hard disk with DOS 5.0 or a later version of DOS installed.)

A.

Invoke QBasic.

1. 2. 3.

Turn on the computer and monitor. At the DOS prompt, type QBASIC and press the Enter key. When the screen querying about the Survival Guide appears, press the Esc key.

Note: If step 2 does not work, enter DIR \QBASIC.EXE /S at the DOS prompt to determine the directory in which QBASIC resides. (Normally, this will be the directory C:\ DOS.) Then enter CD nameOfDirectory and repeat step 2. (For example, in the most common case, enter CD \DOS and then enter QBASIC.) . Allow graphics when the monitor is a Monochrome display that is attached to a Hercules card.

1.

Before invoking QBasic, enter MSHERC at the DOS prompt.

Note 1: If this does not work, enter DIR \MSHERC.COM

/S at the DOS

prompt to determine the directory in which MSHERC resides. (Normally, this will be the directory C:\DOS.) Then enter CD nameOfDirectory and repeat step 1. (For example, in the most common case, enter CD \DOS and then enter MSHERC.) Note 2: The statement SCREEN 3 must appear in any program prior to the use of graphics statements.

C.

Exit QBasic.

1.

Press the Esc key.

2.

Press Alt/F/X.

3.

If the program in the View window has not been saved, QBasic will prompt you about saving it.

Note: In many situations, step | is not needed.

HOW A.

Runa 1.

566

TO: Manage Programs program from QBasic. Press Alt/R/S.

Appendix

G — How To (QBasic)

567

Or,

1.

Press Shift+F5. (Normally, F5 alone will run the program. However, if

the program has been stopped before its end, F5 continues execution from the stopping point, whereas Shift+F5 executes the program from the beginning.)

B.

Save the current program on a disk. 1.

Press Alt/F/S or Alt/F/A.

2.

‘Type the name of the program, if requested, and press the Enter key.

Note: After a program has been saved once, updated versions can be saved under the same name by pressing Alt/F/S. Alt/F/A is used to save the program under a new name. C.

D.

Begin a new program in the View window. 1.

Press Alt/F/N.

2.

If an unsaved program is in the View window, QBasic will prompt you about saving it.

Open a program stored on a disk. 1. 2.

3. E.

Name a program. 1.

HOW

A.

2.

TO: Use the Editor

Look at the pair of numbers at the bottom right of the screen separated by acolon on the status bar. The first number gives the row, and the second number gives the column.

Mark a section of text as a block.

1. 2. 3.

C.

Save it with Alt/F/A.

Determine the row and column position of the cursor. 1.

B.

Press Alt/F/O. Type a filespec into the top rectangle of the dialog box and press the Enter key. Alternately, press the Tab key to penetrate the region containing the names of the files on the disk, and then use the cursor-moving keys and the Enter key to select one of the listed files. If the program in the View window has not been saved, QBasic will prompt you about saving it.

Move the cursor to the beginning or end of the block. Hold down a Shift key and use the direction keys to highlight a block of text. To unblock text, release the Shift key and press a cursor key.

Delete a line of a program. 1. 2.

Or,

Move the cursor to the line. Press Ctrl+Y.

568

Appendix

G— How To (QBasic)

1. 2.

Mark the line as a block. (See item B of this section.) Press Shift+Del.

Note: In the maneuvers above, the line is placed in the clipboard and can be retrieved by pressing Shift+Ins. To delete the line without placing it in the clipboard, mark it as a block and press Del. D.

E.

Move a line within the View window.

1. 2.

Move the cursor to the line and press Ctrl+Y. Move the cursor to the target location.

3.

Press Shift+Ins.

Use the clipboard to move or duplicate statements. 1.

Place the cursor on the first character of the statement (or group of statements).

2.

3. 4. 5. FE.

Search for specific text in program.

1. jes 3. 4. 5. G.

I.

Press Alt/S/E

Type sought-after text into rectangle. Select desired options if different from the defaults. Press the Enter key. ‘To repeat the search, press F3.

Search and change.

Ik 2 3 4. 5. 6. H.

Hold down a Shift key and move the cursor to the right (and/or down) to highlight the selected block of text. Press Shift+Del to delete the block and place it into the clipboard. Or, press Ctrl+Del to place a copy of the block into the clipboard. Move the cursor to the location where you desire to place the block. Press Shift+Ins to place a copy of the text in the clipboard at the cursor.

Press Alt/S/C.

Type sought-after text into first rectangle. Press Tab.

Type replacement text into second rectangle. Select desired options if different from the defaults. Press the Enter key.

Change from “Syntax Checking On” to “Syntax Checking Off’ or vice versa. 1.

Press Alt/O.

2.

“Syntax checking” is preceded by a dot if the feature is active. Press S if you want to change the selection, or press the Esc key to exit.

Check the syntax of a line. (Assuming “Syntax checking” is enabled.) 1.

Move the cursor to the line.

2. 3.

Edit the line in some way. For example, type = and then press Backspace. Press the Down Arrow key.

Note: The syntax of a line is automatically checked whenever the cursor is moved off an edited line, either by pressing the Enter key or a cursor moving key.

Appendix G — How To (QBasic)

J.

Cancel changes made to a line. 1.

Do not move the cursor from the line.

2.

Press Ctrl+Q/L to restore the line to the form it had when the cursor was last moved from the line.

HOW A.

569

TO: Get Help

View the syntax and purpose of a QBasic keyword.

1. 2.

Type the word into the View window. Place the cursor on, or just following, the keyword.

3.

Press Fl.

Or,

B.

C.

1.

Press Alt/H/I/[first letter of keyword].

2. 3.

Use the direction keys to highlight the keyword. Press the Enter key.

Display an ASCII table. 1. 2.

Press Alt/H/C. Press the letter

3.

press the Enter key. Use PgDn and PgUp to move between the extended and standard ASCII character sets.

Obtain a list of common editing and debugging commands. 1.

D.

E.

1.

Press Alt/H/C.

2. 3.

Use Tab and Shift+Tab to highlight a topic. Press the Enter key.

Obtain general information about using the help menu. Press Shift+F1.

Obtain information about the selections in a pull-down menu.

1. G.

Press Alt/H/C/S/Enter.

Obtain other useful reference information.

1.

FE.

A to move the cursor to “ASCII Character Codes” and

See item D in HOW TO: Manage Menus.

Obtain a list of QBasic’s reserved words.

1.

Press Alt/H/I and use the Down Arrow key to scroll through the list.

Note: To obtain information about a word, move the cursor to the word and

press the Enter key.

HOW A.

TO: Manipulate a Dialog Box

Use a dialog box. A dialog box contains three types of items: rectangles, option lists, and command buttons. An option list is a sequence of option buttons of the form (_) option or [ | option, and a command button has the form < command

>.

570

Appendix G — How To (QBasic)

1.

Move from item to item with the Tab key. (The movement is from left to right and top to bottom. Use Shift+Tab instead of Tab to reverse the direction.)

2.

3.

4.

5.

Inside a rectangle, either type in the requested information or use the direction keys to make a selection. Inan option list, an option button of the form ( ) option can be activated with the direction keys. A dot inside the parentheses indicates that the option has been activated. Inan option list, an option button of the form [] option can be activated or deactivated by pressing the space bar. An X inside the brackets indicates that the option has been activated. A highlighted command button is invoked by pressing the Enter key.

Cancel a dialog box.

1.

Press the Esc key.

Or,

1.

HOW

Press the Tab key until the command button < Cancel > is highlighted and then press the Enter key.

TO: Manage Menus

A. Close a pull-down menu. 1.

Press the Esc key.

Open a pull-down menu. 1. 2.

Press Alt. Press the first letter of the name of the menu. Alternately, press the Down Arrow key, use the direction keys to move the highlighted cursor bar to the menu name, and press the Enter key.

- Make a selection from a pull-down menu.

1.

2.

Open the pull-down menu. One letter in each item that is eligible to be used will be emphasized by being highlighted or having a different color than the other letters. Press the emphasized letter. Alternately, use the Down Arrow key to move the cursor bar to the desired item and then press the Enter key.

» Obtain information about the selections in a pull-down menu.

1. 2. 3. 4.

Open the pull-down menu. Use the Down Arrow key to move the highlighted cursor bar to the desired item. The status bar at the bottom of the screen will give a brief description of the item. Pressing Fl gives additional information.

Look at all the menus in the menu bar.

1.

Press Alt/E

2.

Press the Right Arrow key each time you want to see a new menu.

Appendix G — How To (QBasic)

571

HOW TO: Manage Procedures A.

Look at an existing procedure.

1.

Press Shift+F2 repeatedly to cycle through all the procedures.

Or,

1.

Press F2. The top entry is the main body of the program and the remaining entries are procedures.

2.

B.

Use the direction keys and the Enter key to select the desired procedure.

Create a procedure. 1. 2. 3. 4.

Move to a blank line. Type SUB (for a subprogram) or FUNCTION (for a function) followed by the name of the procedure and any parameters. Press the Enter key. (A new window will appear containing the procedure heading and an END statement.) Type the procedure into the new window.

Or,

1.

2.

3. 4.

Press Alt/E/S (for a subprogram) or Alt/E/F (for a function). (A dialog

box will appear.) Type the name of the procedure and any parameters into the Name rectangle. Press the Enter key. (A new window will appear containing the procedure heading and an END statement.) Type the procedure into the new window.

Note: To return to the main body of the program, press F2/Enter. C.

Alter a procedure.

1. 2.

Press Shift+F2 until the desired procedure is displayed. Make changes as needed.

(OM

D.

lL.

Press F2.

2. 3.

Move the cursor bar to the desired procedure. Press the Enter key.

Remove a procedure. IévePress F2. 2. Move the cursor bar to the desired procedure. 3. Press Tab/D/Enter. Insert an existing procedure into a program.

1. 2.

Open the program containing the procedure and press Shift+F2 until the procedure appears on the screen. Mark the procedure as a block. That is, move the cursor to the first statement of the procedure, hold down a Shift key, and move the cursor

1S)

E.

4.

to the last statement of the procedure. Press Ctrl+Ins to place the procedure into the clipboard. Open the program in which the procedure is to be inserted.

572

Appendix

G — How To (QBasic)

5. 6.

HOW A.

Move the cursor to a blank line. Press Shift+Ins to place the contents of the clipboard into the program.

TO: Manage Windows

Change the active window, that is, the window which contains the cursor

and has its title highlighted. 1.

B.

Press F6 until desired window becomes active.

Split a screen to obtain multiple View windows. Option I: Both parts will contain same text. 1.

Press Alt/V/P.

Option II: Second part will contain any procedure. 1. 2. 3. 4. 5.

C.

D.

1.

Use F6 to select window to be retained.

2.

Press Alt/V/P.

Zoom the active window to fill the entire screen.

HOW

Press Alt+Plus to enlarge by one line. Press Alt+Minus to contract by one line.

TO: Alter the Appearance of the View Window

Remove the scroll bars from or add them to the View window. (The scroll bars are needed when a mouse is used.) 1.

Press Alt/O/D/Tab/Tab/Tab.

2.

The space bar can be pressed to alternate between having and not having an X at the cursor. The presence of an X produces scroll bars. Press the Enter key.

3. B.

Press Cel E10: To return window to original size, press Ctrl+F10 again.

Make a small change in the size of the active window. 1. 2.

A.

Alt/V/P. F6. F2. cursor bar to desired procedure. Enter.

Unsplit a screen.

le 2.

E.

Press Press Press Move Press

Change certain colors used by QBasic. 1.

Press Alt/O/D.

2. 3.

Press Tab or Shift+Tab to move around the dialog box. Use the direction keys to make a selection within each region of the dialog box. To change a toggled selection, such as “Scroll bars,” press the Space bar. When all selections have been made, press the Enter key.

4. 5.

Note: When QBasic is exited, these selections will be saved in a file named QB.INI. If this file is present on the same disk and directory as QBASIC.EXE when QBasic is next invoked, it will determine QBasic’s display settings.

Appendix

C.

G — How To (QBasic)

573

Invoke QBasic in black & white.

1.

Type QBASIC /B and press the Enter key when invoking QBasic from DOS.

D. Invoke QBasic with the maximum number of lines supported by the adapter. 1.

HOW

A.

Type QBASIC /H and press the Enter key when invoking QBasic from DOS:

TO: Use the Printer

Obtain a printout of a program. 1. 2.

Press Alt/F/P. Press the Enter key.

Note: To print just the text selected as a block or the active (current) window, use the direction keys to select the desired option. Obtain a printout of a text Output window. 1. 2.

Press F4 to switch to the Output window if necessary. Press Shift+Print Screen. Tip: After the program terminates, the phrase “Press any key to continue” can be removed by pressing F4 twice.

. Obtain a printout of a graphics Output window. The command needed to ready the printer for graphics depends on the type of printer. 1.

(Dot matrix printer) Before invoking QBasic, enter GRAPHICS at the DOS prompt.

Or,

1. 2.

(Laser printer) Before invoking QBasic, enter GRAPHICS HPDEFAULT at the DOS prompt. Press Shift+Print Screen. Tip: After the program terminates, the phrase “Press any key to continue” can be removed by pressing F4 twice.

Note: The above steps will produce an improper printout with certain types of printers. See the discussion of the GRAPHICS graphics command in the DOS reference manual for details.

HOW TO: Use the Debugger A. Stop a program at a specified line. 1.

Place the cursor at the beginning of the desired line.

2.

Press F9. (This highlighted line is called a breakpoint. When the program is run it will stop at the breakpoint before executing the statement.)

Note: To remove this breakpoint, repeat steps 1 and 2.

Remove all breakpoints. 1.

Press Alt/D/C.

574

Appendix

G — How To (QBasic)

C.

Runa

program with each statement highlighted as it is executed.

1.

Press Alt/D.

2.

If the “Trace On” selection is preceded by a mark, press F5. Otherwise, Press T/F5.

Note: To turn off tracing, press Alt/D/T. D.

Run a program one statement at a time. 1. 2.

Press F8. The first executable statement will be highlighted. Press F8 each time you want to execute the currently highlighted statement.

Note: At any time you can view the Output screen by pressing F4. E.

Run the program one statement at a time, but execute each procedure call without stepping through the statements in the procedure one at a time. 1. 2.

Press F10. The first executable statement will be highlighted. Press F10 each time you want to execute the currently highlighted statement.

Note: At any time you can view the Output screen by pressing F4. FE.

Continue execution of a program that has been suspended. 1.

Press F5.

Note: Each time a change is made in a suspended program that prevents the program from continuing, QBasic displays a dialog box with two options to choose from: continue without the change, or restart the program from the beginning. G.

Execute a program up to the line containing the cursor. 1.

H.

Have further stepping begin from the top of the program with all variables cleared. 1.

I.

Press F7.

Press Alt/R/R.

Have further stepping begin at the line containing the cursor (no variables are cleared).

1.

J.

Press Alt/D/N.

Execute a statement from the Immediate window.

1. 2. 3.

Press F6 to move the cursor to the Immediate window. ‘Type the statement into the Immediate window. Press the Enter key with the cursor on the statement.

Appendix H

An Introduction To Windows Pree such as Visual Basic, which are designed for Microsoft Windows, are supposed to be easy to use—and they are once you learn a little jargon and a few basic techniques. This appendix explains the jargon, giving you enough of an understanding of Windows to get you started in Visual Basic. Although Windows may seem intimidating if you’ve never used it before, you only need to learn a few basic techniques, which are covered right here. Mice Pointers

When you use Windows, think of yourself as the conductor and Windows as the orchestra. The conductor in an orchestra points to various members, does something with his or her baton, and then the orchestra members respond in certain ways. For a Windows user, the baton is called the pointing device, most often it is a mouse. The idea is that as you move the mouse across your desk, a pointer moves along the screen in sync with your movements. There are two basic types of mouse pointers you will see in Windows—arrows and hourglasses. The arrow is the ordinary mouse pointer you use to point at various Windows objects before activating them. You will usually be instructed to “move the pointer to...” This really means “move the mouse around your desk until the mouse pointer is at...” The hourglass mouse pointer pops up whenever Windows is saying: “wait a minute; I’m thinking.” This pointer still moves around when you move the mouse, but you can’t tell Windows to do anything until it finishes what it’s doing and the mouse pointer no longer resembles an hourglass. (Sometimes you can press the Esc key to tell Windows to stop what it is doing.)

Note: The mouse pointer can take on many other shapes, depending on which program you are using and what task you are performing. Mouse Actions

Now when you get the (arrow) pointer to a place where you want something to happen, you need to do something with the mouse. There are four basic things you can do with a mouse—pointing, clicking, double-clicking, and dragging. Tip: You can pick the mouse up off your desk and replace it without moving the mouse pointer. This is useful, for example, when the mouse pointer is in the

center of the screen but the mouse is about to fall off your desk! Pointing means moving your mouse across your desk until the mouse pointer is over the desired object on the screen. 519

576

Appendix H — An Introduction To Windows

Clicking (sometimes people say single-clicking) means pressing a mouse button (usually the left button) once and then quickly releasing it. Whenever a sentence begins “Click on,” you need to

1. Move the mouse pointer until it is at the object you are supposed to click on. 2. Press and release the (left) mouse button.

An example of a sentence using this jargon might be “Click on the button marked Yes.” You also will see sentences that begin “Click inside the.” This means to move the mouse pointer until it is inside the boundaries of the object,

and then click. Double-clicking means clicking a mouse button (usually the left button) twice in quick succession (that is, pressing it, releasing it, pressing it, and releasing it again quickly so that Windows doesn’t think you single-clicked twice). Whenever a sentence begins “Double-click on,” you need to:

1. Move the mouse pointer until it is at the object you are supposed to double-click on. 2. Press and release the (left) mouse button twice in quick succession.

For example, you might be instructed to “double-click on the little box at the far left side of your screen.”

Note: An important Windows convention is that clicking selects an object so you can give Windows or the program further directions about it but doubleclicking tells Windows (or the program) to do something. Dragging usually moves a Windows object. If you see a sentence that begins “Drag the,” you need to:

1. Move the mouse pointer until it is at the object. 2. Press the (left) mouse button and hold it down.

3. Now move the mouse pointer until the object moves to where you want it to be.

4. Finally, release the mouse button.

Sometimes this whole activity is called drag and drop.

Starting Windows It’s possible that, when you turn on your computer, Windows starts without your needing to do anything. If this is the case, you’ll see a Windows copyright notice, an hourglass pointer while you wait, and then something that looks like Figure H.1. (Your screen will look a little different because one exciting feature of Windows is that you can change the way it looks to reflect your way of working.) What should remain the same is that the top line of your screen will say “Program Manager.”

Appendix H — An Introduction To Windows

f=

%

577

Program Manager

on 466 # Options

File Manager

Window

Control Panel

a PIF Editor

Help

PrintManager

— Clipboard

Windows Setup

Solitaire

Reversi

4 | @ 228 Read Me

Control

ATM Control

Minesweeper

Accessories

Paintbrush

Figure H.1

Terminal

Notepad

JS

B

Write

Calculator

Recorder

®& Character Map

Program Manager

If instead you see something that looks like this: Ce

then you’re at the (infamous) C prompt. This means that DOS is in control. Type WIN and press Enter to start Windows. If your machine responds with something like “Bad Command,” Windows may not be installed on your machine, in which case. you'll need to get it installed before you can continue! If you know Windows is installed on your system and the above didn’t work, then consult the documentation that came with it—or the guru who decided to set Windows up in a nonstandard way. Windows and its Little Windows

Windows gets its name from the way it organizes your screen into rectangular regions. Each rectangular region in the Program Manager is called a program

group window. The whole region is called the Windows desktop. When you run a program, the program runs inside a bordered rectangular box. Unfortunately Windows jargon calls all of these windows, so there’s only a lower case “Ww” to distinguish them from the program called Windows. Think of a program group window as analogous to organizing your desk efficiently by grouping related piles together—as opposed to keeping all your papers in one unwieldy mess. The Program Manager in the windows desktop starts out with four program windows. When you install a program like Visual Basic, the installation procedure will usually add another program group window to the Program Manager for the program and its files. Each rectangular program group window contains little icons. These icons represent files stored on your computer and are usually called program items. Some of these icons represent programs that you can run, and some represent data stored in your computer. You manipulate a window or the objects represented by the icons inside of it by various combinations of clicking, double-clicking, and dragging.

578

Appendix H — An Introduction To Windows

Starting Programs from the Program Manager The general rule in Windows is that double-clicking on the icon that represents a program usually starts the program. When Windows’ attentions are focused on a specific window, the title bar of the window is highlighted and the window is said to be active. The active window is the only one that can be affected by your actions. An example of a sentence you might see is “Make the window active.” This means if the title bar of the window is not already highlighted, click inside the window. At this point the (new) window will be responsive to your actions. Many title bars contain little buttons that you can click to reduce the window to an icon (minimize it), make it fill up the whole screen (maximize it), or close it entirely. The following title bar shows you what to look for:

Control box

Minimize button

Maximize button

Program Manager

Figure H.2

A Title Bar

Typical jargon you might see might include sentences that begin “Minimize the. .. .” This means to turn the object into an icon. An example of this usage might be “Minimize the Program Manager.” You minimize items to give you more room to see the other objects on your desktop. Similarly, “Maximize the. . .” means to make your object fill the whole screen. You do this when you want to concentrate on only that object. An example of this usage might be “Maximize the Program Manager.” Tip: If you have used the Minimize button to make a window into an icon, double-click on the icon to restore it to its previous size.

If you have maximized a window, the Maximize button changes to look like a double-headed arrow called the Restore button. Click on this button to return the window to its previous size.

Tip: You can close any window by double-clicking on the control box. You can also close the active window by holding down the Alt key and pressing the F4 function key. When you close the Program Manager window by double-clicking in its Control box (or using Alt+F4), Windows

itself starts to shut down. You are

presented with the message box for shutting down Windows. Click on the OK button if you want to shut down Windows,

and click on the button marked

Cancel if you don’t want to shut down Windows. Finally, as long as the window isn’t maximized, you can usually move an active window around the screen by dragging its title bar. (Recall that this means to move the mouse pointer until it is in the title bar, hold down the left mouse button, move the mouse until the window is where you want it to be, and then release the mouse button.)

Note: You can also drag the icons inside a window to rearrange them.

Appendix H — An Introduction To Windows

579

Resizing a Window You can change the size of a window by minimizing, maximizing, or restoring it. In addition, you can change the size of most windows to exactly suit your needs. To adjust the size of a non-maximized window: 1. Move the mouse pointer until it is at the place on the boundary you want to adjust. The mouse pointer changes to a double-headed arrow.

2. Drag the border to the left or right or up and down to make it smaller or larger. Which border you want to effect determines which one you drag.

3. When you are satisfied with the new size of the window, release the left mouse button. Scroll Bars

If a window or other Windows object contains more information than can fit on the screen, you need a way to move through this information so you can see it all. For example, you will certainly be writing procedures in Visual Basic that are longer than one screen. You can use the mouse to march through your code with small steps or giant steps. A vertical Scroll bar lets you move from the top to the bottom of the Window; a horizontal Scroll bar lets you move within the left and right margins of the window. Use this scroll bar when the contents of the window are too wide to fit on the screen. Figure H.3 shows both vertical and horizontal Scroll bars.

Case "1" Let flag$

Case "2" Let flag$ Case

Let

Figure H.3

i 1519-1685"

= “France

1685-1696"

= “Mexico

1821-1836"

Vertical scroll bar

"3"

flag$

Case "4" Let flag$ Case "5"

Scroll box

“Spain

Scroll box

+]

Sub GetFlag (a$, flag$) Rem Six Flags of Texas Select Case a$

“Republic

of

Texas

1836-1845"

Horizontal scroll bar

A Visual Basic Code Window

As you can see, a scroll bar has two arrows at the end of a channel that also contains a little box (usually called the Scroll box). The Scroll box is the key to

moving rapidly; the arrows are the key Dragging the Scroll box enables you to approximate location in your window. For to the middle of the channel, you'll scroll window.

to moving in smaller increments. quickly move long distances to an example, if you drag the Scroll box to approximately the middle of your

580

Appendix H — An Introduction To Windows

Menus

The jargon is to say that Windows programs are menu driven. This just means that you can control the features of the program by choosing items from menus. If you tried to close a window by double-clicking but only clicked once on the control box by mistake you may have seen the Control menu shown here: Restore Move

Maximize

Figure H.4

Close

Alt+FA

Switch To...

CtrltEsc

Control Menu

The jargon says “The menu is dropped down” (or “pulled down”). Once a menu is dropped down, there are two ways to pick a menu item (the jargon says “choose the item” or “activate the item”). 1. Click on the item.

2. Use the Up Arrow and Down Arrow keys to move through the list of menu items. Each item is successively highlighted. Press Enter when you get to the item you want to choose. For example, the jargon might say: “An alternate way to close a window is to drop down the Control Menu and choose Close.” Every Windows program has a main menu bar that runs right below the title bar; this is how you activate the program’s features. (In contrast, the Control Menu lets you manipulate the window that the program is sitting in.)

The menu bar for Program Manager in Figure H.1 contains four items. One way to open a menu is to move the mouse pointer to the name of the menu and click. This has the disadvantage that you have to take your hands off the keyboard temporarily. Windows also makes it easy to open a menu with the keyboard. The easiest way to open a menu using the keyboard is to look for the underlined letter of the desired option in the menu bar and then to press Alt and the underlined letter. Underlined letters are usually called accelerator keys or hotkeys. For example, if the Program Manager window is active, press Alt+F to open the File menu shown here.

New... Open Move...

Enter F7

Copy... Delete

F8 Del

Properties...

Alt+Enter

Exit Windows...

Figure H.5

The Program Manager File Menu

Appendix H — An Introduction To Windows

581

Notice that all of these menu items have underlined access keys. You can just press the letter while the menu is open to select the command. (For example, you can press “X” to exit Windows.) Tip: You can activate a menu item in one step if you know its access key. For

example, if you press the Alt key, the F key and the X key in succession, Windows opens the File menu and chooses the Exit item. Some items like Move or Properties have keys (or key combinations) listed

to their right. These are called shortcut keys. A shortcut key is a key or combination of keys you can press to activate an item without opening a menu. Some

menu

items have

a three-dot ellipsis after their names

(like Exit

Windows in the screen above). The ellipsis indicates that choosing the item is not enough: You need to do more work. Usually choosing one of these options displays a dialog box that you will need to work with. Dialog boxes allow you to give the program a lot more information than a simple click on a button can do. We cover dialog boxes in the next section. Finally, if you cannot use a menu item at the moment, it will appear grayed and clicking on it will have no effect. The jargon is to say that the menu item is disabled.

Finding Program Groups from the Program Manager’s Window menu As you install more Windows programs, you may no longer be able to see the program group window that contains the program you want to work with. There is a surefire method of finding a program group window—if you remember its name: 1. Choose Window from the Program Manager’s main menu bar (remember you can do this by pressing Alt/W). This drops down a (long) list of items. If the program group is listed on this list, click on it or type the number to the left of its name. If not, click on the More Windows item and look through the next list (and so on as needed) until

you find the program group you want. Windows opens the program group window for the item you selected.

Starting Programs from the Program Manager’s File Menu The general rule in Windows is that double-clicking on the icon that represents a program usually starts the program—but suppose you can’t find the icon. As with program group windows, there is a surefire method of starting a program—if you can remember its name. To do this, open the File menu in the Program Manager and choose Run (Alt/F/R). This opens a little dialog box. Now type

the name of the program in the box labeled Command Line and click on the OK button. (You will usually need the full name of the program in order for this to work; for Visual Basic Primer Edition this is most likely C: \WBPRIMER \ VB.)

Dialog Boxes Working with a dialog box is probably the most common task you will do with a program in order to get it to do what you want. In the previous section, you

582

Appendix

H — An Introduction To Windows

saw the Run dialog box available from the File menu in the Program Manager. Generally, you need to fill in the information requested in the dialog box or close it before you can continue working with the program. Almost all dialog boxes have a command button marked Cancel that you can click on if you decide you don’t want to work with the dialog box. Often you can press the Esc key to achieve the same effect. Caution: Dialog boxes frequently have a button that goes into effect when you press Enter. This is often but not always the OK button. You can tell which button will be activated when you press Enter by looking for the button with a bold outline around it. (The jargon calls this the default command button for the dialog box or just the default button.) Note: If a command button has an underlined access key in its name, you can press Alt and then the access key to have the same effect as clicking on the button. This is useful when you don’t want to take your hands off the keyboard.

The Open and Save Dialog Boxes In Windows programs, you will also encounter dialog boxes for working with files. Here is the Open dialog box from Visual Basic, which is typical of the dialog boxes you'll see for working with files.

Open Project File Name:

Directories: c:\vbprimer

autoload. mak

project] mak text] mak

List Files of Type:

Project Files(MAK)

Figure H.6

||

An Open Dialog Box

Most of the elements in these dialog boxes are the same as you saw in the previous section. There are command buttons, a couple of check boxes, dropdown list boxes for List Files of Type, Drives, and so on. For example, if you click on the drop-down list box marked Drives, you see a list of drives on your machine. You would now click on the drive to tell Windows to look at the files contained in the new drive. The list of file names on the left side of the Open dialog box is an example of an ordinary list box. The idea is you click once to select a file in this list box (it will then fill the text box marked File Name), or you can double-click to

actually open the file.

Appendix H — An Introduction To Windows

583

Remember: The Windows convention is that clicking on an item selects it; double-clicking activates it. Obviously, what “activate” means depends on the dialog box. In our example, double-clicking a file in a dialog box called Open would, naturally enough, open it.

The Directories list box ina file handling dialog box works a little differently than a regular list box. Think of a directory as a kind of file in a giant filing cabinet. These files are special in that they can contain other files—which can in turn contain other files and so on. The little icons next to the name of the directories make this clear. The file icon is shown as open if Visual Basic is looking at files inside this “cabinet.” You can have a whole chain of these open filing cabinets (also know as open directories), When you see the directory you want the program to look for files in, double-click on its name. If the directory contains other directories, doubleclicking forces the program to look at only those directories above and below the directory you clicked on. If the directory contains other directories, this forces the programs attention deeper into the cabinet. The jargon for this is “To move up and down the directory tree.” You should also be aware that the jargon sometimes talks about subdirectories. This is simply a directory that is inside another directory. The directory that contains the subdirectory is called the parent directory. The top directory is called the root directory. Note: All Windows programs automatically update the File Name list whenever you move up the directory tree by double-clicking or change drives via the Drives drop-down list box.

Ending Windows To close Windows from the Program Manager, hold down the Alt key and the F4 function key at the same time. (That is, Press Alt+F4.) You are presented

with a message box that looks like this:

Exit Windows

e

Figure H.7

This will end your Windows session.

Dialog Box for Ending Windows

Click on the OK command button if you want to shut down Windows, or click on the command button marked Cancel (or press Esc) if you don’t want to leave Windows. Caution: It is a bad idea to end Windows by just shutting off your machine.

Appendix I

How To (Visual Basic) HOW

TO: Install, Invoke, and Exit Visual Basic

Install the Primer Edition of Visual Basic onto a hard disk.

A.

. Invoke Windows. Insert the Primer Edition diskette into one of the drives, say the A drive. . Invoke Window’s Program Manager if it is not already invoked. Press Alt/F/R to execute the Run command from the File menu.

. Type A:\ VBPRIMER\SETUP into the Command Line box. . Press the Enter key or click on the OK button. . After a few seconds a Welcome screen will appear. Press the Enter key to continue.

8. A Location screen will appear. Press the Enter key to use the default directory as displayed. 9. When you are advised that the directory does not yet exist, press the Enter key to allow the creation of the directory. 10. When the Installation Complete screen appears, press the Enter key to proceed and invoke Visual Basic. .

Install the Standard or Professional edition of Visual Basic onto a hard disk.

SS se Pees

1. 2.

-

Invoke Windows Place the first (Setup) Visual Basic diskette into one of the diskette drives, say the A drive. Invoke Window’s Program Manager if it is not already invoked. Press Alt/F/R to execute the Run command from the File menu.

Type A:\SETUP and press the Enter key. Follow the directions given by SETUP.

Invoke Visual Basic after installation.

1.

Invoke Windows.

2. 3.

Invoke Window’s Program Manager if it is not already invoked. Double-click on the Visual Basic icon.

Note: The first time you invoke Visual Basic, the ToolBox may not be visible.

If so, press Alt/W/T to display it. . Exit Visual Basic.

1.

Press the Esc key.

2.

Press Alt/F/X.

3.

If an unsaved program is present, Visual Basic will prompt you about saving it.

Note: In many situations, Step | is not needed. 584

Appendix I — How To (Visual Basic)

HOW A.

Runa

1.

585

TO: Manage Programs program from Visual Basic.

Click on the Run icon (right arrowhead).

Or, 1.

B.

Press Alt/R and make a selection from the Run menu.

Save the current program on a disk. 1.

Press Alt/F/V.

2.

Fill in the requested information. Do not give an extension as part of the project name or the file name. Two files will be created—one with extension .MAK and the other with extension .FRM. The .MAK file holds a list of files related to the project. The .FRM file actually holds the program.

Note: After a program has been saved once, updated versions can be saved under the same name by pressing Alt/F/V. Alt/F/E is used to save the program under a new name. C.

Begin a new program. 1.

Press Alt/F/N.

2.

If an unsaved program is present, Visual Basic will prompt you about saving it.

D.

Open a program stored on a disk. 1.

Press Alt/F/O.

2.

Type a filespec into the top rectangle of the dialog box and press the Enter key. Alternatively, press the Tab key to penetrate the region containing the names of the files on the disk, and then use the direction keys and the Enter key to select one of the listed files. (If an unsaved program is present, Visual Basic will prompt you about saving it.)

Note: The form for the project does not appear, but the title of the Project window shows that the project has been opened. E.

Display the form associated with a program. 1. 2.

FE

Name a program. 1}

G.

Press Alt/W/R to activate the Project window. Click on View Form.

SSaveit.

Save a program as a text file readable by other word processors. 1.

Press Alt/F/A.

2.

Ifthe box preceding the phrase Save as Text is not marked with an X, then click in the box or press Alt+S. Make any other desired changes to the information displayed regarding the saving of this program. Click on Ok. The .FRM file for the program is now a text file.

3. 4.

Appendix I — How To (Visual Basic)

HOW A.

TO: Use the Editor

Mark a section of text as a block.

1. 2.

Move the cursor to the beginning or end of the block. Hold down a Shift key and use the direction keys to highlight a block of text.

3.

Release the Shift key.

Or,

1.

Move the mouse to the beginning or end of the block.

2.

Hold down the left mouse button and move the mouse to the other end of the block. Release the left mouse button.

3.

Note: To unblock text, press a direction key or click outside the block. . Delete a line of a program. 1. 2.

Move the cursor to the line. Press Ctrl+Y.

Or,

1. 2.

Mark the line as a block. (See item A of this section.) Press Shift+Del.

Note: In the maneuvers above, the line is placed in the clipboard and can be retrieved by pressing Shift+Ins. To delete the line without placing it in the clipboard, mark it as a block and press Del. - Move a line within the Code window.

1. 2.

Move the cursor to the line and press Ctrl+Y. Move the cursor to the target location.

3.

Press Shift+Ins.

. Use the clipboard to move or duplicate statements.

1. 2. 3. 4.

Mark the statements as a block. Press Shift+Del to delete the block and place it into the clipboard. Or, press Ctrl+Ins to place a copy of the block into the clipboard. Move the cursor to the location where you desire to place the block. Press Shift+Ins to place a copy of the text from the clipboard at the cursor.

BB

Whe

. Search for specific text in program.

Mm

586

Press Alt/E/E Type sought-after text into rectangle.

Select desired options if different from the defaults. Press the Enter key. To repeat the search, press F3.

Appendix

I — How To (Visual Basic)

587

Search and change.

ON

Press Alt/E/R.

Type sought-after text into first rectangle. Press Tab. Type replacement text into second rectangle. Select desired options if different from the defaults. Press the Enter key.

. Check the syntax of a line.

1. 2. 3.

Move the cursor to the line. Edit the line in some way. For example, type = and then press Backspace. Press the Down Arrow key.

Note: The syntax of a line is automatically checked whenever the cursor is moved off an edited line either by pressing the Enter key or a direction key. . Cancel changes made to a line. 1.

Press Alt/E/U to undo the last set of changes made to the most recently edited line.

Note: A set of changes is all changes made to a line without moving the cursor off the line. Moving the cursor off a line ends the current set of changes and causes the syntax of the line to be checked.

HOW TO: Get Help (Standard and Professional Editions only) A. View the syntax and purpose of a Visual Basic keyword. 1. 2.

Type the word into the Code window. Place the cursor on, or just following, the keyword.

3.

Press Fl.

Or, 1.

Press Alt/H/S

2. 3.

Type in the keyword or term of interest and press the Enter key. Double click on the topic of interest in the second list.

Display an ANSI table. 1. 2. 3.

Press Alt/H/S. Type ANSI and press the Enter key twice. Press the Tab key followed by the Enter key to move between the displays for ANSI characters 0-127 and 128-255.

. Obtain general help on designing a form. 1.

Press Alt/H/C.

2. 3.

Click on Creating the Interface. Click on the topic of interest in the window that appears.

. Obtain general help on setting properties. 1.

Press Alt/H/C.

588

Appendix I — How To (Visual Basic)

2. 3.

E.

Click on Setting Properties. Click on the topic of interest in the window that appears.

Obtain general help on writing and debugging code. 1. Ub Press Alt/H/C.

2. 3. E

Obtain other useful reference information.

1. 2.

G.

Click on Writing and Debugging Code. Click on the topic of interest in the window that appears.

Press Alt/H/C. Click on the topic of interest.

Obtain general information about using the Help menu. 1. 2.

Press Alt/H/C and then press Alt/H/H. Click on the topic of interest.

H. Obtain information about the selections in a pull-down menu. 1. I.

See item D in HOW TO: Manage Menus.

Obtain a list of Visual Basic’s reserved words.

1.

Press Alt/H.

2. 3.

Click on Programming Language in the Reference list. Click on the first letter of the keyword(s) of interest, or use the mouse with the vertical elevator to scroll through the list.

Oe

1. 2.

Place the cursor on a blank line in the Code window and press F1. Proceed as in step 2 above.

Note: To obtain information about a keyword, click on it. When finished, close this window by pressing Alt/F/X J.

Exit Help. 1.

HOW

Press Alt/F/X.

TO: Manipulate a Dialog Box

See Appendix G. In Visual Basic, ( ) becomes a circle, [ ] becomes a square, and becomes a command button.

HOW A.

TO: Manage Menus

Open a pull-down menu. 1.

Click on the menu name.

Or,

1.

Press Alt.

2.

Press the first letter of the name of the menu. Alternatively, use the Right Arrow key to move the highlighted cursor bar to the menu name, then press the Down Arrow key.

Appendix I — How To (Visual Basic)

B.

589

Make a selection from a pull-down menu.

1. 2.

Open the pull-down menu. Click on the desired item.

Or,

1. 2. C.

E.

1.

Press Alt/E

2.

Press the Right Arrow key each time you want to see a new menu.

Close a pull-down menu.

HOW

2.

2. 3.

Mark the section of code as a block as described in the HOW the Editor section. Press Ctrl+Ins.

TO: Use

Hold down the Alt key and repeatedly press the Tab key until Program Manager appears, then release the Alt key. Double click on the Accessories icon. Double click on the Notepad icon.

Display all characters in a font.

WAR wD

1.

D.

TO: Utilize the Windows Environment

Access Windows’ Notepad. 1.

C.

Press the Esc key or click anywhere outside the menu.

Place a section of code in the Windows clipboard. 1.

B.

Press Fle Click on name of the menu of interest. Click on selection of interest.

Look at all the menus in the menu bar.

1.

A.

pull-down menu. One letter in each item that is eligible to be be underlined. underlined letter. Alternatively, use the Down Arrow key to cursor bar to the desired item and then press the Enter key.

Obtain information about the selections in the pull-down menu currently displayed. (Not available with Primer Edition.) ler 2. 3.

D.

Open the used will Press the move the

Hold down the Alt key and repeatedly press the Tab key until Program Manager appears, then release the Alt key. Double click on the Accessories icon. Double click on the Character Map icon. Click on the underlined down arrow at the right end of the Font box. Highlight the desired font and press the Enter key or double click on the desired font.

Display an ANSI or ASCII code for a character with a code above 128.

1.

Proceed as described in item C of this section to display the font containing the character of interest.

Appendix I — How To (Visual Basic)

IE

Click on the character of interest. Displayed at the right end of the bottom line of the font table is Alt+Oxxx, where xxx is the code for the character.

E.

Temporarily go to DOS.

ae

le

OE

590

HOW A.

TO: Design a Form

Display the ToolBox. ile

B.

Hold the Alt key down and repeatedly press the Tab key until Program Manager appears, then release the Alt key. Double click on the Main icon. Double click on the MS-DOS Prompt icon. Enter one or more desired commands at the DOS prompt. Enter EXIT to return to Windows. Hold the Alt key down and repeatedly press the Tab key until Microsoft Visual Basic appears, then release the Alt key.

Press Alt/W/T.

Place a new control on the form.

Option I: (new control with default size and position) ih

2

Double click on the control’s icon in the ToolBox. The new control appears at the center of the form. Size and position the control as described in item H below.

Option II: (a single new control sized and positioned as it is created) ip a 3.

4.

5, 6.

Click on the control’s icon in the ToolBox. Move the mouse to the approximate position on the form desired for the upper-left corner of the control. Press and hold the left mouse button. Move the mouse to the position on the form desired for the lower-right corner of the control. A dashed box will indicate the overall shape of the new control. Release the left mouse button. The control can be resized and repositioned as described below.

Option III: (create multiple instances of the same control) if 2;

3s C.

Click on the control’s icon in the ToolBox while holding down the Ctrl key. Repeatedly use steps 2 through 5 of Option II to create instances of the control. When finished creating instances of this control, click on the arrow icon in the ToolBox.

Create a related group of controls. ibs

a

To hold the related group of controls, place a PictureBox control (top right in ToolBox) on the form. Use Option II or II in item B of this section to place controls on the PictureBox.

Appendix I — How To (Visual Basic)

D.

591

Set the focus to a particular control.

1.

Click on the control.

Or

1. E.

FE.

Delete a control. 1.

Set the focus to the control to be deleted.

2.

Press the Del key.

Delete a related group controls. 1. 2.

G.

2.

3.

3.

Set the focus to the Move the mouse to edge of the control. which points in the Drag to the desired

desired control. one of the eight sizing handles located around the The mouse pointer will change to a double arrow direction that resizing can occur. size.

Set the focus to the form. Move the mouse to the edge or corner of the form that is to be stretched or shrunk. The mouse pointer will change to a double arrow which points in the direction that resizing can occur. Drag to the desired size.

Use the color palette to set foreground and background colors.

1.

Set the focus to the desired control or the form.

2.

Press Alt/W/C to activate the Color Palette.

3.

If the Color Palette obscures the object you are working with, you may wish to use the mouse to grab the Color Palette by its title bar and move it so that at least some of the object shows. To set the foreground color, click on the square within a square at the far left in the Color Palette. To set the background color, click on the region within the outer square but outside the inner square. Click on the desired color from the palette.

4.

5.

HOW A.

the

Change the size of a form.

1. 2.

J.

Move the mouse onto the control, the PictureBox containing related group of controls, or the title of the from. Drag the object to the new location.

Change the size of a control. 1. 2.

I.

Set the focus to the PictureBox holding the related group of controls. Press the Del key.

Move a control, related group of controls, or form to a new location. 1.

H.

Press the Tab key until the control receives the focus.

TO: Work with the Properties of an Object

Activate the Properties window. 1.

Press Alt/W/O.

592

Appendix I — How To (Visual Basic)

Or, 1.

Press F4.

. Highlight a property in the Properties window. 1. 2.

Activate the Properties window and press the Enter key. Use the Up or Down Arrow keys to move the highlight bar to the desired property.

Or,

1. 2.

3.

Activate Click on bar at the is visible. Click on

the Properties window. the up or down arrow located at the ends of the vertical scroll right side of the Properties window until the desired property

the desired property.

. Select or specify a setting for a property. 1. 2.

Highlight the property whose setting is to be changed. Click on the settings box or press Tab to place the cursor in the settings box.

aE a.

b.

c.

Ifa black, underlined down arrow appears at the right end of the settings box. Use the Up or Down Arrow keys to display the allowed settings for the property. When the desired setting is displayed, press the Enter key. Alternatively, click on the down arrow at the end of the settings box to display a list of all allowed settings, then click on the desired setting. If an ellipsis (three periods: . . .) appears at the right end of the settings box. Press F4 or click on the ellipsis to display a dialog box or a color palette. Answer the questions in the dialog box and click on Ok, or click on the desired color in the color palette. If a gray, underlined down arrow appears at the right end of the settings box. Type in the new setting for the property.

Note: The settings box refers to the second box below the title “Properties.” It is preceded by X and check mark icons. . Change a property setting of an object. 1. 2. 3. 4.

Set the focus to the desired object. Activate the Properties window . Highlight the property whose setting is to be changed. Select or specify the new setting for the property.

Let a label change size to accommodate its caption. 1.

Set the label’s AutoSize property to True. (The label will shrink to the smallest size needed to hold the current caption. If the caption is changed, the label will automatically grow or shrink to accommodate the new caption.)

Appendix I — How To (Visual Basic)

593

Let a label caption use more than one line. 1.

Set the label’s WordWrap property to True. (If the label is not wide enough

to accommodate

the entire caption on one line, part of the

caption will wrap to additional lines. If the label height is too small, then part or all of these wrapped lines will not be visible.)

. Let a text box display more than one line.

1.

Set the text box’s MultiLine property to True. (If the text box is not wide enough to accommodate the text entered by the user, the text will scroll down to new lines. If the text box is not tall enough, lines will scroll up out of view, but can be redisplayed by cursoring up.)

. Assign a hot key to a label or command button.

1.

When assigning a value to the Caption property, precede the desired hot key character with an ampersand (&).

Place the initial focus on a particular command button. 1.

Set the command button’s Default property to True.

WR WN

Adjust the order in which the Tab key moves the focus. Set the focus to the first object in the tabbing sequence. Change the setting of the TabIndex property for this object to 1. Set the focus to the next object in the tabbing sequence. Change the setting of the TabIndex property for this object to 2. Repeat steps 3 and 4 until all objects on the form have been assigned a new TabIndex setting.

. Allow the pressing of Esc to activate a particular command button. 1.

Set the command button’s Cancel property to True. (Setting the Cancel property True for one command button automatically sets it False for all other command buttons.)

HOW A.

Access the Code Window.

1.

B.

TO: Manage Procedures

Press the Esc key followed by F7. (It is not always necessary to press the Esc key.)

Look at an existing procedure. 1. 2.

Access the Code Window. Press Ctrl+Down Arrow or Ctrl+Up Arrow repeatedly to cycle through all the procedures.

Or, 1.

Access the Code Window.

2.

Press F2. The top entry is the declarations section of the program and the remaining entries are procedures. Use the direction keys and the Enter key to select the desired procedure.

3.

594

Appendix I — How To (Visual Basic)

C.

Create a procedure. Access the Code Window. Move to a blank line.

Type SUB (for a subprogram) or FUNCTION (for a function) followed by the name of the procedure and any parameters. Press the Enter key. (The Code Window will now display the new procedure heading and an END statement.) Type the procedure into the Code Window.

6. D.

Alter a procedure. L.

Z. E.

2;

3:

Bring the procedure into the Code Window as described in item B of this section. Mark the entire procedure as a block. That is, press Ctrl+Home to move the cursor to the beginning of the procedure, then hold down a Shift key and press Ctrl+End to move the cursor to the end of the procedure. Press the Del key.

Insert an existing procedure into a program.

1. 2. 3. 4. 5. 6. 7.

HOW A.

Bring the procedure into the Code Window as described in item B of this section. Make changes as needed.

Remove a procedure.

Ie

FE.

Access the Code Window. Press Alt/V/N. (A dialog box will appear.) Type the name of the procedure into the Name rectangle. Select the type of procedure (subprogram or function) by clicking on the procedure type or pressing Alt+S for a subprogram or Alt+F for a function. Press the Enter key. (The Code window will now display the new procedure heading and an END statement.) Type the procedure into the Code Window.

Open the program containing the procedure. Bring the procedure into the Code Window as described in item B of this section. Mark the entire procedure as a block. Press Ctrl+Ins to place the procedure into the clipboard. Open the program in which the procedure is to be inserted and access the Code Window. Move the cursor to a blank line. Press Shift+Ins to place the contents of the clipboard into the program.

TO: Manage Windows

Zoom the active window to fill the entire screen.

IW

Click on the maximize (up arrow) button in the upper-right corner of the active window.

Appendix I — How To (Visual Basic)

2.

To return the window to

595

its original size, click on the restore (double

arrow) button that has replaced the maximize button. B.

Move a window.

iE dp

C.

Move the mouse to the title bar of the window. Drag the window to the desired location.

Change the size of a window. i. ee

HOW

Move the mouse to the edge of the window which is to be adjusted or to the corner joining the two edges to be adjusted. When the mouse becomes a double arrow, drag the edge or corner until the window has the desired size. TO: Use the Printer

A. Obtain a printout of a program when using the Primer Edition of Visual Basic.

1.

Save the program in a form readable by other word processors (i.e., in a text file).

2. 3.

Access Windows’ Notepad. Press Alt/F/O to specify a file to open.

4.

If desired, enter *.FRM to see a list of form files saved in the current

5.

6. 7.

B.

directory. Type in the name under which the program is saved, or press the Tab key to penetrate the displayed list of files, then highlight the desired file name. In either case, press the Enter key to open the file. Press Alt/F/P to print the program. Press Alt/F/X to close Notepad, then hold down the Alt key and press the Tab key repeatedly until Microsoft Visual Basic appears, then release the Alt key.

Obtain a printout of a program when using the Standard or Professional Edition of Visual Basic. ibe Me

Press Alt/F/P.

Press the Enter key.

Note: To print just the text selected as a block or the active (current) window, use the direction keys to select the desired option. C.

Obtain a printout of the form during runtime.

it

Place the statement PrintForm in the Form_Click() or other appropriate procedure of the program at the point when the desired output will be on the form.

HOW A.

TO: Use the Debugger

Stop a program at a specified line. 1s toy

Place the cursor at the beginning of the desired line. Press F9. (This highlighted line is called a breakpoint. When the program is run it will stop at the breakpoint before executing the statement.)

Note: To remove this breakpoint, repeat steps 1 and 2.

596

Appendix I — How To (Visual Basic)

B.

Remove all breakpoints. 1.

Press Alt/D/L.

C. Run a program one statement at a time. 1. 2.

Press F8. The first executable statement will be highlighted. Press F8 each time you want to execute the currently highlighted statement.

Note: The Code Window may need to be reduced and/or moved in order to see the output appearing on the form. Also, to guarantee that output is retained while stepping through the program, the AutoRedraw property of the form and any picture boxes may need to be set to True. Run the program one statement at a time, but execute each procedure call without stepping through the statements in the procedure one at a time. 1. 2.

Press Shift+F8. The first executable statement will be highlighted. Press Shift+F8 each time you want to execute the currently highlighted statement.

Continue execution of a program that has been suspended. 1)

(Press. F5.

Note: Each time an attempt is made to change a suspended program in a way that would prevent the program from continuing, Visual Basic displays a dialog box warning that the program will have to be restarted from the beginning and gives the option to cancel the attempted change.

Have further stepping begin at the line containing the cursor (no variables are cleared). 1.

Press Alt/D/N.

Appendix J

Visual Basic Statements, Events,

Functions, Methods, Properties, Data Types, and Operators his appendix applies to the following objects: form, printer, text box, command button, label, and picture box. The last four are also called controls. Terms in brackets follow some of the discussions. These terms refer to supporting topics presented at the end of this appendix.

Abs

See Appendix C.

Alignment The Alignment property of a text box or label affects how the text assigned to the Text property is displayed. If the Alignment property is set to 0 (the default), then text is displayed left justified, if set to 1, then text is right

justified, and if set to 2, then text is centered. And

(Logical Operator) See Appendix C.

And

(Bitwise Operator) See Appendix C.

Asc

Characters are stored as numbers from 0 to 255. If a$ is astring of characters,

then Asc(a$) is the number corresponding to the first character of a$. For any n from 0 to 255, Asc(Chr$(n)) is n.

Atn

See Appendix C.

AutoRedraw The AutoRedraw property determines what happens to graphics and Printed material on a form or picture box after another object (for example, another picture box) temporarily obscures part of the form or picture box. If AutoRedraw is True, then Visual Basic will restore the graphics and Printed material from a copy that it has saved in memory. If AutoRedraw is False, then Visual Basic does not keep track of what graphics and Printed material have been obscured, but does invoke the Paint event of the form or picture box when the obstruction is removed. Thus only graphics and Printed material generated by the Paint event will be restored when AutoRedraw is False.

AutoSize Ifthe AutoSize property of a label is True, then Visual Basic automatically sets the width and height of the label so that the entire caption can be accommodated. If the AutoSize property is False, then the size of the label is not adjusted by Visual Basic, and captions are clipped if they do not fit. BackColor The BackColor property determines the background color of an object. For a Command Button, the background color is the color of the dotted rounded rectangle that surrounds the caption when the command button has the focus. If the BackColor of a form or picture box is changed while a program 597

598

Appendix J — Visual Basic Statements

is running, all graphics and Printed text directly on the form or picture box are erased. BackStyle The BackStyle property of a label is opaque (1) by default. The rectangular region associated with the label is filled with the label’s background color and caption. If the BackStyle is set to transparent (0), then whatever is behind the label remains visible; the background color of the label essentially becomes “see through.” Beep

See Appendix C.

BorderStyle The BorderStyle property determines the type of border on a form, label, picture box, or text box. A BorderStyle of 0 results in no border. This is the default for labels. A BorderStyle of 1 produces a single-line border. This is the default for a picture box or text box. For forms, a BorderStyle of 1 also means that the size of the form cannot be changed by the user when the program is running. For forms, the default BorderStyle is 2 which produces a single-line border and allows the user to change the size of the form when the program is running. Finally, for forms, a BorderStyle of 3 produces a double-line border which cannot be resized by the user. Call

See Appendix C.

Cancel The Cancel property provides a means of responding when the user presses the Esc key. At most one command button on a form may have its Cancel property set to True. If the Esc key is pressed while the program is running, then Visual Basic will execute the click event procedure of the command button whose Cancel property is True. Caption The Caption property holds the text which is to appear as the caption for a form, command button, or label. If an ampersand (&) is placed in the caption of acommand button or label, then the ampersand will not be displayed, but the character following the ampersand will become a hot key. Hot keys provide a quick way to access a command button or the control (usually a text box) following (in tab index order) a label. Hot keys are activated by holding down the Alt key and pressing the hot key character.

CCur The function CCur converts integer, long integer, single-precision, and double-precision numbers to currency numbers. If x is any number, then the value of CCur(x) is the currency number determined by x. CDbl

ChDir

See Appendix C.

See Appendix C.

ChDrive The statement ChDrive drive$ changes the default drive to the drive specified by drive$. For example, ChDrive “A” specifies the A drive as the new default drive. Chr$ If n is a number from 0 to 255, then a statement of the form objectName.Print Chr$(n) displays the nth character of the current font.

CInt

See Appendix C.

Circle The graphics method objectName.Circle (x,y),7,c,r1,r2,a draws on objectName a portion, or all, of an ellipse as describe for the Circle statement in

Appendix C. If k is a number corresponding to one of the 16 standard colors

Appendix J — Visual Basic Statements

599

listed in footnote [5] of Appendix C, then using QBColor(k) for c will produce

an ellipse in color k. In general, c may be any valid RGB color. [color] Clear The method ClipBoard.Clear clears the clipboard, setting its contents to the null string. Click The Click event applies to command buttons, picture boxes, labels, and forms. A Click event occurs whenever the left mouse button is pressed and released while the mouse cursor is over the control, or over a blank area on the form. In the case of a command button, the Click event is also called if the

spacebar is pressed while the command button has the focus, or if the button’s access key is used. CLng

See Appendix C.

Close

See Appendix C.

Cls The method formName.Cls clears the form formName of all text and graphics which have been placed directly on the form with methods like formName.Print, formName.Circle, etc. The method pictureBox.Cls clears the named picture box. The Cls method resets the CurrentX and CurrentY properties of the cleared object to the coordinates of the upper left corner (usually

(0,0)). Const

See Appendix C.

Control The Control data type may be used in the parameter lists of Sub and Function definitions to allow the passing of control names to the procedure. ControlBox The ControlBox property determines whether or not a form has a ControlBox button in the upper left corner. If the ControlBox property is set to True (the default), then the ControlBox button is displayed. Among the opera-

tions available from the ControlBox menu is the ability to close the form and thereby end the program. If the ControlBox property of a form is set to false, then the ControlBox button is not displayed. Since, in this case, the user cannot end the program using the ControlBox or by pressing Alt+F4, it is important to provide a command button for this purpose.

Cos CSng

See Appendix C. See Appendix C.

CStr The function CStr converts integer, long integer, single-precision, double-precision, currency, and variant numbers to strings. If x is amy number, then the value of CStr(x) is the string determined by x. Unlike the Str$ function,

CStr does not place a space in front of positive numbers. [variant] CurDir$

The value of the function CurDir$(drive$) is a string specifying the

current directory on the drive specified by drive}. The value of CurDir$(“”) or CurDir$ is a string specifying the current directory on the default drive. Currency The currency data type is extremely useful for calculations involving money. A variable of type Currency requires 8 bytes of memory and can hold any number from —922,337,203,685,477.5808 to 922,337,203,685,477.5807 with at most four decimal places. Currency values and variables are indicated by the type tag @: 21436587.01@, Balance@.

600

Appendix J — Visual Basic Statements

CurrentX, CurrentY The properties CurrentX and CurrentY give the horizontal and vertical coordinates of the point on a form or picture box at which the next Print or graphics method will begin. Initially, CurrentX and CurrentY are the coordinates of the upper left corner of the form or picture box. The default coordinate system defines the upper left corner of the form or picture box as (0,0), with x increasing from left to right and y increasing from top to bottom in twips. After a graphics method, (CurrentX, CurrentY) are the coordinates of

the last point referenced. CVDate The function CVDate converts a numeric or string expression to an equivalent serial date. If x is any expression representing a valid date, then the value of CVDate(x) is the serial date determined by x. Valid numeric values are —657434 (January 1, 100 AD.) to 2958465 (December 31, 9999). Valid string

expressions either look like one of these valid numeric values (e.g. “19497” corresponding to May 18, 1953) or look like a date (e.g., “10 Feb 1955”, “August 13, 1958”, etc.) [date]

CVar The function CVar converts strings and integer, long integer, single-precision, double-precision, and currency numbers to variants. If x is any string or number, then the value of CVar(x) is the variant determined by x. [variant]

Date$

See Appendix C.

DateSerial The value of the function DateSerial(year,month,day) is the serial date corresponding to the given year, month, and day. Values from 0 to 9999 are acceptable for year, with 0 to 99 interpreted as 1900 to 1999. Values of 1 to 12

for month, and 1 to 31 for day are normal, but any Integer value is acceptable. Often, numeric expressions are used for month or day which evaluate to numbers outside these ranges. For example, DateSerial(1993, 2, 10 + 90) is the date 90 days after Feb. 10, 1993. [date] DateValue

The value of the function DateValue(a$)

is the serial date corre-

sponding to the date given in a$. DateValue recognizes the following date formats: “2-10-1955”,“2/10/1955”, “February 10, 1955”, “Feb 10, 1955”, “10-Feb1955”, and “10 February 1955”. For the years 1900 through 1999, the initial “19” is optional. [date]

Day The function Day extracts the day of the month from a serial date. If d is any valid serial date, then the value of Day(d) is an integer from 1 to 31 giving the day of the month recorded as part of the date and time stored in d. [date] DblClick The DblClick event applies to picture boxes, labels, and forms. A DblClick event occurs whenever the left mouse button is pressed and released twice, in quick succession, while the mouse cursor is over the control, or over a

blank area on the form. Double-clicking on an object will first cause that object’s Click event to occur, followed by its DblClick event.

Default When the Default property of a command button is set to True and the focus is on an object that is not another command button, then pressing the Enter key has the same effect as clicking on the button. At most one command button on a form can have True as the value of its Default property.

DefInt, DefLng, DefSng, DefDbl, DefStr, DefCur, DefVar See Appendix C for a general discussion of DefType statements. The statements DefCur and

Appendix J] — Visual Basic Statements

601

DefVar specify which starting letters for the names of variables are to identify the default variable types currency and variant respectively. DefType statements are placed in the declarations section of (general). [variant]

Dim See Appendix C for a general discussion of Dim. Visual Basic also permits currency and variant variables. Variables and arrays Dimmed in the declarations section of (general) are available to all procedures. In procedures, Dim may be used to declare variables, but ReDim must be used to dimension arrays. [variant] Dir$ If fileTemplate$ then the value of the matching the pattern then the value of the

specifies function specified function

a file (or a collection of files by including ? or *), Dir$(fileTemplate$) is the filespec of the first file by fileTemplate$. If this value is not the null string, Dir$ is the next file that matches the previously

specified pattern. For example, the value of Dir$(“*.BAS”) will be a string specifying the first file in the current directory of the default drive whose name

has the .BAS extension.

Do/Loop

See Appendix C.

DoEvents Executing the statement DoEvents permits Visual Basic to act upon any events which may have occurred while the current event procedure has been executing.

Double

See Appendix C.

DrawMode

The property DrawMode determines whether graphics are drawn

in black, white, foreground color, or some interaction of these colors with the

current contents of the form or picture box. The following table lists the allowed values for the DrawMode property and the rules for what RGB color number will be assigned at a given point when the RGB color number for the color currently displayed at that point is display and the RGB color number for the draw color is draw. [color] DrawMode

Color produced

1

&HO00000000& (Black)

2

Not draw And Not display

3

display And Not draw

(inverse of #14)

4

Not draw

(inverse of #13)

5

draw And Not display

(inverse of #12)

6

Not display

(inverse of #11)

7

draw Xor display

8

Not draw Or Not display

7

draw And display

—_ (inverse of #15)

(inverse of #9)

10

Not (draw Xor display)

(inverse of #7)

11

display

(transparent)

12

display Or Not draw

13

draw

14

draw Or Not display

15

draw Or display

16

SHOOFFFFFF& (White)

(draw color)

602

Appendix J — Visual Basic Statements

DrawStyle

When DrawWidth is 1 for a form or picture box (the default), the

property DrawStyle determines whether graphics are drawn using a solid line or some combinations of dots and dashes. Use a DrawStyle of 0 (the default) for solid lines, 1 for dashed lines, 2 for dotted lines, 3 for dash-dot lines, or 4 for

dash-dot-dot lines. A DrawStyle of 5 produces “invisible” graphics. When thick lines are drawn as a result of setting Draw Width to values greater than 1, graphics are always drawn using solid lines. In this case, DrawStyle can be used to either center the thick line over where line with a DrawWidth of 1 would be drawn or, when drawing closed figures like ellipses and rectangles, to place the thick line just inside where the line with a Draw Width of 1 would be drawn. To draw thick graphics inside the normal closed figure, use a DrawStyle of 6. DrawStyles | through 4 will center thick graphics over the normal location. DrawWidth The property DrawWidth determines the width in pixels of the lines which are drawn by graphics methods. The default is 1 pixel. Values from 1 to 32,767 are permitted.

Enabled The property Enabled determines whether or not a form or control responds to events. If the Enabled property of a form or control is set to True (the default), then if an event occurs for which an event procedure has been

written, then the event procedure will be executed. When the Enabled property of a form or control is set to False, all events relating to that control are ignored;

no event procedures are executed. End

See Appendix C.

EndDoc

The method Printer.EndDoc is used to indicate that the document

currently being printed is complete and should be released to the printer.

Environ$

See Appendix C.

Eof See Appendix C. Eqv Erase

See Appendix C. See Appendix C.

Err and Erl Err Error

(Functions) See Appendix C.

(Statement) See Appendix C. See Appendix C.

Error$ The value of the function ERROR$ is the error message corresponding to the run-time error which has most recently occurred. The value of the function ERROR$(errnum) is the error message corresponding to the run-time error designated by errnum. Exit

See Appendix C.

Exp

See Appendix C.

False A predefined constant whose value is 0. False is used when setting the value of properties that are either True or False. For example, Picturel.FontlItalic = False. FileAttr

See Appendix C.

Appendix J — Visual Basic Statements

FileCopy

603

The statement FileCopy source$, destination$ creates the file specified

by destination$ by making a copy of the file specified by source$. Both source$ and destination$ may specify drive and path information. If the file specified by destination$ already exists, it will be overwritten without a warning being issued. FileDateTime

The value of the function FileDateTime(filename$)

is a string

giving the date and time that the file specified by filename$ was created or last modified. FileLen The value of the function FileLen(filename$) is the length in characters (bytes) of the file specified by filename$.

FillColor When the FillStyle property of a form or picture box is set to a value other than the default of 1, the property FillColor determines what color is used to paint the interior of ellipses and rectangles drawn with the Circle and Line graphics methods. The FillColor property may be set using the QBColor function or any valid RGB color. The default value for FillColor is black (0). [color]

FillStyle The property FillStyle determines what pattern is used to paint the interior of ellipses and rectangles drawn on forms or picture boxes with the Circle and Line methods. The default value for FillStyle is transparent (1), which

means that interiors are not painted. Other values available for FillStyle are solid (0), horizontal lines (2), vertical lines (3), diagonals running upwards to the

right (4), diagonals running downwards to the right (5) vertical and horizontal lines [cross hatched] (6), and diagonal cross hatched (7). Note: Using BF in a

Line method has the same effect as setting the FillStyle to 0 and the FillColor to the color of the bordering line. Fix

See Appendix C.

FontBold The property FontBold determines whether or not the characters Printed on a form, picture box, or printer, or assigned to a text box, command button, or label appear in bold or normal type. If the FontBold property is set to True (the default), then for a form, picture box, or printer, subsequent Printed characters appear bold. For a text box, command button, or label, the text or caption is immediately changed to bold. If the FontBold property is set to False, then subsequent characters are Printed in normal type while characters assigned to the text or caption property change immediately to normal type. FontCount The value available for use on Printer.FontCount is FontCount property is ally used to determine

of the property Screen.FontCount is the number of fonts the screen. Similarly, the value of the property the number of fonts available on the printer. The set according to your Windows environment, and generthe limit on the index for the Fonts property.

FontlItalic The property FontItalic determines whether or not the characters Printed on a form, picture box, or printer, or assigned to a text box, command button, or label appear in italic or upright type. If the Fontltalic property is set to True, then for a form, picture box, or printer, subsequent characters appear in italic. For a text box, command button, or label, the text or caption is immediately changed to italic. If the Fontltalic property is set to False (the default), then subsequent characters are Printed in upright type while characters assigned to the text or caption property change immediately to upright type.

604

Appendix J — Visual Basic Statements

FontName The property FontName determines what type face is used when characters are Printed on a form, picture box, or printer, or assigned to a text box, command button, or label. If the FontName property of a form, picture box, or printer is set to a font obtained from the Fonts property, then all subsequently Printed characters will appear in the new type face. When the FontName property of a text box, command button, or label is set to a new font, characters assigned to the text or caption property change immediately to the new type face. Fonts The value of the property Screen.Fonts(fontNum) is the name of a screen font available in the current Windows environment. The index fontNum can range from 0 to Screen.FontCount—1. Similarly, the value of the property Printer.Fonts(fontNum) is the name of an available printer font. The values in the Fonts property are set by your Windows environment, and are generally used to determine which fonts are available for setting the FontName property. FontSize The property FontSize determines the size, in points, of characters Printed on forms, picture boxes, and the printer or displayed in text boxes and on command buttons and labels. Available font sizes depend on your Windows environment, but will always be between 1 and 2048. Default font sizes are usually between 8 and 12 point. Note: One point equals 1/72nd of an inch. FontStrikeThru The property FontStrikeThru determines whether or not the characters Printed on a form, picture box, or printer, or assigned to a text box, command button, or label appear in a strikethru or standard font. If the FontStrikeThru property is set to True, then for a form, picture box, or printer, subsequent Printed characters appear with a horizontal line through the middle of each character. For a text box, command button, or label, the text or caption

is immediately changed so that a horizontal line goes through the middle of each character. If the FontStrikeThru property is set to False (the default), then subsequent characters are Printed in standard type while characters assigned to text or caption property change immediately to standard type.

FontTransparent The property FontTransparent determines the degree to which characters Printed to forms and picture boxes obscure existing text and graphics. If the FontTransparent property is set True (the default), the existing text and graphics is only obscured by the dots (pixels) needed to actually form the new character. If the FontTransparent property is set False, then all text and graphics are obscured within the character box (small rectangle surrounding a character) associated with the new character. Those dots (pixels) not needed to

form the character are changed to the background color. FontUnderline The property FontUnderline determines whether or not the characters printed on a form, picture box, or printer, or assigned to a text box, command button, or label appear with an underline. If the FontUnderline property is set to True, then for a form, picture box, or printer, subsequent characters Printed appear underlined. For a text box, command button, or label, the text or caption is immediately changed to underlined. If the FontUnderline property is set to False (the default), then subsequent characters are Printed

without underlines while characters assigned to the text or caption property change immediately to non-underlined. For/Next

See Appendix C.

Appendix J — Visual Basic Statements

605

ForeColor The property ForeColor determines the color used to display text, captions, graphics, and Printed characters. If the ForeColor property of a form or picture box is changed, then subsequent characters will appear in the new color. For a text box, command button, or label, then immediately changed to the new color. [color]

text or caption

is

Format$ The value of the function Format$(expression, a$) is a string representing expression (a number, date, time, or string) formatted according to the

tules given by a$. Format$ is useful when assigning values to the Text property and when Printing to a form, picture box, or the printer. Numeric output can be formatted with commas, leading and trailing zeros, preceding or trailing signs (+ or —), and exponential notation. This is accom-

plished either by using for af the name of one of several predefined numeric formats or by combining in af one or more of the following special numeric formatting characters: #, 0, decimal point (period), comma, %, E-, and E+. The

expression to be formatted can evaluate to one of the numeric types or a string representing a number. Predefined numeric formats include “General Number” which displays a number as is; “Currency” which displays a number with a leading dollar sign, commas every three digits to the left of the decimal, displays two decimal places, and encloses negative numbers in parentheses; “Fixed” which displays two digits to the right and at least one digit to the left of the decimal point; “Standard” which displays a number with commas and two decimal places but does not use parentheses for negative numbers; “Percent” which multiplies the value by 100 and displays a percent sign after two decimal places; and “Scientific” which displays numbers in standard scientific notation. For example, Format$(5432.352, “Currency”) gives the string “($5,432.35)”.

The symbol # designates a place for a digit. If the number being formatted does not need all the places provided by the #’s given in a$, then the extra #’s are ignored. The symbol 0, like #, designates a place for a digit. However, if the number being formatted does not need all the places provided by the 0’s given in a$, then the character 0 is displayed in the extra places. If the number being converted has more whole part digits than there is space reserved by #’s and 0’s, then additional space is used as if the format string had more #’s at its beginning. For example, Format$(56, “####”) yields “56”, Format$(56, “#”) yields “56”, Format$(0, “#”) yields “’, Format$(56, “O000”) yields “0056”, Format$(56, “O”) yields “56”, and Format$(0, “O”) yields “O”. The decimal point symbol (.) marks the location of the decimal place. It

separates the format rules into two sections, one applying to the whole part of the number and the other to the decimal part. When included in the format string, a decimal point will always appear in the resulting string. For example, Format$(56.246, “#.4#”) yields “56.25”, Format$(.246, “#.##”) yields “.25”, Format$(.246, “O.#¥#”) yields “0.25”, and Format$(56.2, “0.00”) yields “52.20”. The comma symbol (,) placed to the left of the decimal point between #’s

and/or 0’s causes commas to be displayed to the left of every third digit to the left of the decimal point, as appropriate. If commas are placed to the immediate left of the decimal point (or to the right of all #’s and 0’s when the decimal point symbol is not used), then before the number is formatted, it is divided by 1000 for each comma, but commas will not appear in the result. In order to divide by 1000s and display commas in the result, use format strings like “#,#,.00”, which

606

Appendix J] — Visual Basic Statements

displays the number with commas in units of thousands, and “#,#,,.00”, which

displays the number with commas in units of millions. For example, Format$(1234000, “#,#”) yields “1,234,000”, Format$(1234000, “#,”) yields “1234”, Format$(1234000, “#,.”) yields “1234.”, Format$(1234000, “#,,.0”) yields “1.2”, and Format$(1234000, “#,0,.0”) yields “1,234.0”.

The percent symbol (%) placed to the right of all #’s, 0’s, and any decimal point causes the number to be converted to a percentage (multiplied by 100) before formatting and the symbol % to be displayed. For example, Format$(.05624, “#.##%”) yields “5.62%”, and Format$(1.23, “#%”) yields “123%”.

The symbols E+ and E- placed to the right of all #’s, 0’s, and any decimal point causes the number to be displayed in scientific notation. Places for the digits in the exponent must be reserved to the right of E+ or E— with #’s or O's. When E+ is used and the exponent is positive, a plus sign appears in front of the exponent in the result. When E- is used and the exponent is positive, no sign or space precedes the exponent. When scientific notation is used, each position reserved by #’s to the left of the decimal point is used whenever possible. For example, Format$(1234.56, “#.##E+##”) yields “1.23E+3”, Format$(1234.56, “aH ##E—##”) yields “12.34E2”, Format$(1234, “###.00E+##”) yields “123.40E+1”, and Format$(123, “#4*E+00”) yields “123E+00”.

Date & time output can be formatted using numbers or names for months, putting the day, month, and year in any order desired, using 12 hour or 24 hour notation, etc. This is accomplished either by letting a$ be the name one of several predefined date/time formats or by combining in a$ one or more special date/time formatting characters. The expression to be formatted can evaluate to a number which falls within the range of valid serial dates or to a string representing a date/time. Predefined date/time formats include “General Date” which displays a date in mm/dd/yyyy format and, if appropriate, a time in hh:mm:ss PM format; “Long Date” which displays the day of week, the full name of month, the day, and a four digit year; “Medium Date” which displays the day, abbreviated month name,

and two digit year; “Short Date” which displays mm/dd/yy“; ”Long Time“ which displays the time in hh:mm:ss PM format; "Medium Time“ which displays time in hh:mm PM format; and ”Short Time which display time in 24 hour format as hh:mm. For example, let dt = DateSerial(55,2,10) + TimeSerial(21,45,30). Then Format$(dt, “General Date”) yields “2/10/55 9:45:30 PM”, Format$(dt, “Medium Date”) yields “10-Feb-55”, and Format$(dt, “Short Time”) yields

2145". Format symbols for the day, month, and year include d (day as number but no leading zero), dd (day as number with leading zero), ddd (day as three letter name), dddd (day as full name), m (month as number but no leading zero), mm (month as number with leading zero), mmm (month as three letter name),

mmmm (month as full name), yy (year as two-digit number), and yyyy (year as four-digit number). Separators such as slash, dash, and period may be used as desired to connect day, month, and year symbols into a final format. For example, Format$(“August 13, 1958”, “dddd, d.mmm.yy”) yields “Wednesday, 13.Aug.58” and Format$(“July 4, 1776”, “ddd: mmmm dd, yyyy”) yields “Thu: July 04, 1776”. Additional format symbols for dates include w (day-of-week as number 1-7), ww

(week-of-year as number 1-53), q (quarter-of-year as number 1-4), y (day-of-year as number 1-366), ddddd (same as short date), and dddddd (same as long date).

Appendix J — Visual Basic Statements

607

Format symbols for the second, minute, and hour include s (seconds with no leading zero), ss (seconds as two-digit number), n (minutes with no leading zero), nn (minutes as two-digit number), h (hours with no leading zero), hh (hours as two-digit number), AM/PM (use 12 hour clock and uppercase), am/pm (use 12 hour clock and lowercase), A/P (use 12 hour clock and single uppercase letter), a/p (use 12 hour clock and single lowercase letter), and ttttt (same as general date). Separators such as colons and periods may be used as desired to connect hour, minute, and second symbols into a final format. For example, Format$ (“14:04:01”, “h:nn AM/PM”) yields “2:04 PM”, Format$(“14:04:01”, “h.n.s”) yields “14.4.1”, and Format$(0.75, “h:nna/p”) yields “6:00p”.

String output can be formatted as all uppercase, all lowercase, left-justified or right justified. Symbols used to format strings are @ (define a field for at least as many characters as there are @ symbols; if less characters than @ symbols, fill remainder of field with spaces; if more characters than @ symbols, display the extra characters—don'’t clip), & (reserve space for entire output string), < (convert all characters to lowercase before displaying), > (convert all characters to uppercase before displaying), ! (left justify within field defined by @ symbols; default is to right justify). For example, Format$(“Red”, “@”) yields “Red”, Format$(“Red”, “@@@@@@"”) yields“ — Red” (3 leading spaces), Format$(“Red”, _” (3 trailing spaces), and Format$(“Red”, “@@@@@@") yields “RED

yields “red”. FreeFile

Function

See Appendix C.

See Appendix C.

Get (Files) See Appendix C. Note: The buffer method of working with random-access files is not available in Visual Basic. GetAttr

The value of the function GetAttr(filename$) is a number indicating

the file attributes associated with the file specified by filename$. Let attrib be a variable holding the value returned by GetAttr. Then the file specified by filename$ is a read-only file if attrib And 1 = 1, is a hidden file if attrib And 2 = 2, is a system file if attrib And 4 = 4, is a volume label if attrib And 8 = 8, is a

directory name if attrib And 16 = 16, or has been modified since the last back-up if attrib And 32 = 32.

GetText The value of the method ClipBoard.GetText is a string containing a copy of the data currently stored in the clipboard. GoSub See Appendix C. Note: Both the GoSub statement and its target must be in the same procedure. GotFocus The GotFocus event applies to command buttons, text boxes, and picture boxes. A GotFocus event occurs when an object receives the focus, either through a user action or through code, via the SetFocus method.

GoTo See Appendix C. Note: The GoTo statement and its target must be in the same procedure.

Height The property Height determines the vertical size of an object. Height is measured in units of twips. For the Printer object, Height may be read (ph = Printer.Height is OK) but not assigned (Printer.Height = 100 causes an error).

Hex$

See Appendix C.

608

Appendix J — Visual Basic Statements

Hour The function Hour extracts the hours from a serial date. If d is any valid serial date, then the value of Hour(d) is a whole number from 0 to 23 indicating the hours recorded as part of the date and time store in d. [date]

If (single line)

See Appendix C.

See Appendix C.

If (block)

If TypeOf To test for the type of a control when the control name is passed to a procedure, use If TypeOf controlName Is controlType Then action! Else action2 in either the single line or block form of the If statement. Elself TypeOf is also permitted. For controlType, use one of the control names which appear in the Form Design ToolBox (CommandButton, Label, TextBox, etc.) For example, If

TypeOf objectPassed Is Label Then... . Imp

See Appendix C.

Input#

See Appendix C.

Input$ The statement a$ = Input$(n,m) assigns the next n characters from the file with reference number m to a.

InputBox$ The value of the function InputBox$(prompt$) is the string entered by the user in response to the prompt given by prompt$. The InputBox$ function automatically displays the prompt, a text box for user input, an OK button, and a Cancel button in a dialog box in the center of the screen. If the user selects Cancel, the value of the function is the null string (“”). For greater control, use the function InputBox$(prompt$, title}, default$, xpos, ypos) which titles the dialog box with title$, displays default$ as the default value in the text box, and

positions the upper left corner of the dialog box at coordinates (xpos, ypos) on the screen. Instr See Appendix C. Int See Appendix C. Integer

See Appendix C.

IsDate

The

value of the function IsDate(a$)

is True

(-1)

if the string a$

represents a date between January 1, 100 and December 31, 9999. Otherwise, the value is False (0). [date] IsEmpty

The value of the function IsEmpty(v) is True (-1) if v is a variable of

unspecified type (i-e., is a variant) which has not yet been assigned a value. In all other cases the value of IsEmpty is False (0). [variant] IsNull

The value of the function IsNull(v) is True (-1) if v is a variant variable

which has been assigned the special value Null. In all other cases the value of IsNull is False (0). [variant]

IsNumeric

The value of the function IsNumeric(v) is True (—1)

if v is a number,

numeric variable, or a variant variable which has been assigned a number or a string which could be obtained by Formatting a number. In all other cases the value of IsNumeric is False (0). [variant]

KeyPress The KeyPress event applies to command buttons, text boxes, and picture boxes. A KeyPress event occurs whenever the user presses a key while one of the above controls has the focus. A code identifying which key was pressed

Appendix J] — Visual Basic Statements

609

will be passed to the event procedure in the KeyAscii parameter. This information can then be used to determine what action should be taken when a given key is pressed.

Kill See Appendix C.

LBound

See Appendix C.

LCase$

See Appendix C.

Left The property Left determines the position of the left edge of a form or control. The units of measure are twips for forms. The units of measure for a control are determined by the ScaleMode property of the container (form, picture box, etc.) upon which the control has been placed, with the position of

the control measured from the edge of its container using the coordinate system established by the various Scale. . . properties for the container. By default, the unit of measure for a container is twips, with a value of O for the Left property placing the control against the left edge of the container. Left$ Len

See Appendix C. See Appendix C. If var is a variant variable, then Len(var) is the number

of bytes needed to store var as a string. [variant] Let Line

See Appendix C. The graphics method objectName.Line (x1,y1)—(x2,y2),c,rect,s draws a line

or rectangle on objectName as describe for the Line statement in Appendix C. If k is a number corresponding to one of the 16 standard colors listed in footnote [5] of Appendix C, then using QBColor(k) for c will produce a line or rectangle in color k. In general, c may be any valid RGB color. [color] Line Input#

See Appendix C.

Load The Load event applies only to forms and occurs only once, immediately when a program starts. This is the appropriate place to put code that should be executed every time a program is run, regardless of the user’s actions. LoadPicture The statement objectName.Picture = LoadPicture(pictureFile$), where objectName is a form or picture box, places the picture defined in the file

specified by pictureFile$ on objectName

Loc Lock

See Appendix C. See Appendix C.

Lof

See Appendix C.

Log

See Appendix C.

Long

See Appendix C.

LostFocus The LostFocus event applies to command buttons, text boxes, and picture boxes. A LostFocus event occurs when an object loses the focus, either through a user action or through code, via the SetFocus method. LSet

Ifa$ is astring variable, then the statement LSet a$ = b$ replaces the value

of a$ with a string of the same length consisting of b$ truncated or padded on the right with spaces. LSet also can be used to assign a record of one user-defined type to a record of a different user-defined type.

610

Appendix J — Visual Basic Statements

LTrim$

See Appendix C.

MaxButton The MaxButton property determines whether or not a form has a maximize button in the upper right corner. If the value of the MaxButton property is set to True (the default), a maximize button is displayed when the program is run. The user then has the option to click on the maximize button to cause the form to enlarge and fill the entire screen. If the value of the MaxButton property is set to False, then the maximize button is not displayed when the program is run, and the user is thus unable to “maximize” the form. MaxLength The property MaxLength determines the maximum number of characters that a text box will accept. If the MaxLength property for a text box is set to 0 (the default), then an unlimited number of characters may be entered in the text box.

Mid$

See Appendix C.

MinButton The MinButton property determines whether or not a form has a minimize button in the upper right corner. If the value of the MinButton property is set to True (the default), a minimize button is displayed when the program is run. The user then has the option to click on the minimize button to cause the form to be replaced by a small icon at the bottom of the screen. If the value of the MinButton property is set to False, then the minimize button is not displayed when the program is run, and the user is thus unable to “minimize” the form.

Minute The function Minute extracts the minutes from a serial date. If d is any valid serial date, then the value of Minute(d) is a whole number from 0 to 59 giving the minutes recorded as part of the date and time stored in d. [date] MkDir Mod

Month

See Appendix C. See Appendix C.

The function Month extracts the month from a serial date. If d is any

valid serial date, then the value of Month(d)

is a whole number from 1 to 12

giving the month recorded as part of the date and time stored in d. [date]

MousePointer The property MousePointer determines what shape the mouse pointer takes when the mouse is over a particular form or control. Valid values for the MousePointer property are whole numbers from 0 to 12. A value of 0 (the default) indicates that the mouse pointer should take on the normal shape for the control it is over. (The normal shape over text boxes is an I-beam, while for a form, picture box, label, or command button it is an arrow.) Use a MousePointer value of 1 for an arrow, 2 for cross-hairs, 3 for an I-beam, 4 for a small square

within a square, 5 for a four-pointed arrow, 6 for a double arrow pointing up to the right and down to the left, 7 for a double arrow pointing up and down, 8 for a double arrow pointing up to the left and down to the right, 9 for a double arrow pointing left and right, 10 for an up arrow, 11 for an hourglass, and 12 for a “do not” symbol (circle with diagonal line). Move The control so positioning positioning

method objectName.Move xpos, ypos moves the named form or that its upper left corner has coordinates (xpos, ypos). For forms, is relative to the upper left corner of the screen. For controls, is relative to the upper left corner of the form, frame, or picture box

Appendix J — Visual Basic Statements

611

to which the control is attached. The method objectName.Move xpos, ypos, width,

height also resizes the named form or control to be width units wide and height units high. The Move method may be used whether or not a form or control is visible. If you wish to specify just a new width for an object, you CANNOT use objectName.Move ,,width. Instead, use objectName.Move objectName.Left, object-

Name.Top, width. Similar considerations apply for changing just ypos, height, width and height, etc. MsgBox

(Statement and Function) The statement MsgBox(message$) displays

message$ in a dialog box with an OK button. The more general statement MsgBox(message$, buttons, title$) displays message$ in a dialog box titled with title$ and containing from one to three buttons as determined by the value of buttons. The value of buttons also determines which button is the default (has the focus) and which if any of 4 icons is displayed. The value to use for buttons can be computed as follows: buttons = set number + default number + icon number

where set number, default number and icon number are determined from the following tables: Buttons Set

Set Number

OK OK, Cancel Abort, Retry, Ignore Yes, No, Cancel Yes, No

0 1 2 3 4

Retry, Cancel

5

Focus Default

Default Number

First Button Second Button Third Button

@) 256 Sly

Icon

Icon Number

Stop sign Question mark

16 32

Exclamation mark Information

48 64

The value of the function MsgBox(message$, buttons, title$) indicates which of the displayed buttons the user pushed; in all other aspects the MsgBox statement

and function act in the same manner. The values returned for each of the possible buttons pressed are | for OK, 2 for Cancel (or Esc), 3 for Abort, 4 for Retry, 5

for Ignore, 6 for Yes, and 7 for No. MultiLine The property MultiLine determines whether or not a text box can accept and display multiple lines. If the MultiLine property of a text box is set to True, then text entered in the text box will wrap to a new line when the right side of the text box is reached. Pressing the Enter key will also start a new line. If the MultiLine property of a text box is set to False (the default), then input is restricted to a single line which scrolls if more input is entered than can be displayed within the width of the text box.

612

Appendix J — Visual Basic Statements

Name (Property) The property Name is used at design time to give a meaningful name to a form or control. This new name will then be used by Visual Basic in naming all event procedures for the form or control. Name (Statement) See Appendix C. NewPage

The method Printer.NewPage

indicates that the current page of

output is complete and should be sent to the printer. A form feed (Chr$(12))

will also be sent to the printer to cause the paper to advance to the top of a new page. Not

(Logical Operator) See Appendix C.

Not

(Bitwise Operator) See Appendix C.

Now

The value of the function Now() is the serial date for the current date and

time as recorded on the computer’s internal clock. [date]

Oct$

See Appendix C.

On Error See Appendix C. Note: The On Error statement and its target must be in the same procedure. On. . .GoSub and On. . .GoTo See Appendix C. Note: The On. . .GoSub or On. . .GoTo statement and its target must be in the same procedure. Open

See Appendix C.

Option Base

See Appendix C.

Option Compare

The statement Option Compare Text, placed in the declara-

tions section of (general), causes string comparisons to be case insensitive. Thus,

if Option true. The produces character

Compare Text is in effect, the comparison “make” = “MaKe” will be statement Option Compare Binary placed in the declarations section the default comparison rules which are case sensitive and use the order given in the ANSI/ASCII character tables.

Option Explicit

If the statement Option Explicit appears in the declarations

section of (general), then each variable must be declared before it is used. A

variable is declared by appearing in a Const, Dim, Global, ReDim, or Static statement, or by appearing as a parameter in a Sub or Function definition. Or

(Logical Operator) See Appendix C.

Or

(Bitwise Operator) See Appendix C.

Picture The property Picture allows a form or picture box to be assigned a picture or icon for display. If iconOrPicture is a file defining an icon or bitmapped picture, then objectName.Picture = LoadPicture(iconOrPicture) places the icon

or picture on the form or picture box identified by objectName. Point The value of the method objectName.Point(x,y) is the RGB number of the color of the point with coordinates (x,y) on the form or picture box identified

by objectName. Thus if the point with coordinates (x,y) has been painted using color RGB(7,g,b), then the value of Point(x,y) will be r+256*g+65536*b. If the

coordinates (x,y) identify a point which is not on objectName, then the value of Point(x,y) will be —1. [color]

Appendix J — Visual Basic Statements

613

Print The method objectName.Print displays information on the form, printer, or picture box identified by objectName in much the same manner as described for the Print statement in Appendix C. In Visual Basic, there is no limit to the number of characters or the number of print zones on a line. Printer The Printer object provides access to the printer. Methods available are Print to send text to the printer, NewPage to execute a form feed to begin a new

page, EndDoc to terminate the printing process, and the graphics methods. Many properties available for forms and picture boxes, such as fonts and scaling, are also available for the printer.

PrintForm The method formName.PrintForm prints on the printer an image of the named form and all its contents. PSet

The graphics method objectName.PSet(x,y) displays the point with coor-

dinates (x,y) in the foreground color. The method objectName.PSet(x,y),c causes

the point (x,y) to be displayed in the RGB color specified by c. The size of the point is determined by the value of the Draw Width property. The actual color(s) displayed depend on the values of the DrawMode and DrawStyle properties. [color]

Put (Files)

See Appendix C. Note: The buffer method of working with random-

access files is not available in Visual Basic.

QBColor The value of the function QBColor(colorAttrib) is the RGB color number associated with the QBasic color attribute colorAttrib. Valid values for colorAttrib are whole numbers from 0 to 15. This function is included in Visual Basic for easy access to QBasic’s 16 standard colors. [color]

Randomize

See Appendix C.

ReDim See Appendix C. ReDim may only be used within procedures; it may not be used in the declarations section of (general). To establish a global array which may be resized, Dim it with empty parentheses in the declarations section of (general) and then ReDim it as needed within appropriate procedures. Refresh The method objectName.Refresh causes the named form or control to be refreshed, that is, redrawn reflecting any changes made to its properties. Generally, refreshing occurs automatically, but if not, it may be forced with the Refresh method.

Rem

See Appendix C. See Appendix C.

Reset Resume Return RGB

See Appendix C. See Appendix C.

The value of the function RGB(red, green, blue) is the color number

corresponding to a mixture of red red, green green, and blue blue. This color number is assigned to color properties or used in graphics methods to produce text or graphics in a particular color. Each of the three color components may have a value from 0 to 255. The color produced using RGB(0,0,0) is black, RGB(255,255,255) is white, RGB(255,0,0) is bright red, RGB(10,0,0) is a dark

red, etc. (The value of the function RGB(7,g,b) is the long integer r+256*g+ 65536*b.) [color]

614

Appendix J] — Visual Basic Statements

Right$

See Appendix C.

RmDir

See Appendix C.

Rnd

See Appendix C.

RSet If a$ is a string variable, then the statement RSet a$ = b$ replaces the value of a$ with a string of the same length consisting of b$ truncated or padded on the left with spaces.

RTrim$ Scale

See Appendix C.

The method objectName.Scale (x1, yl) — (x2, y2) defines a coordinate

system for the form or picture box identified by objectName. This coordinate system has horizontal values ranging from x1 at the left edge of objectName to x2 at the right edge and vertical values ranging from yl at the top edge of objectName to y2 at the bottom edge. Subsequent graphics methods and control positioning place figures and controls in accordance with this new coordinate system. As a result of using the Scale method, the ScaleMode property of objectName is set to 0, the ScaleLeft property to x1, the ScaleTop property to yl, the ScaleHeight property to y2~yl, and the ScaleWidth property to x2—x1. The method objectName.Scale without arguments resets the coordinate system of objectName to the standard coordinate system where the unit of measure is twips and the upper left corner of objectName has coordinates (0,0).

ScaleHeight The property ScaleHeight determines the vertical scale on a form or picture box. After the statement objectName.ScaleHeight = hght is executed, the vertical coordinates range from objectName.ScaleTop at the top edge of objectName to objectName.ScaleTop + hght at the bottom edge. The default value of the ScaleHeight property is the height of objectName when measured in the units specified by objectName’s ScaleMode property.

ScaleLeft The property ScaleLeft determines the horizontal coordinate of the left edge of a form or picture box. After the statement objectName.ScaleLeft = left is executed, the horizontal coordinates will range from left at the left edge of objectName to left + objectName.ScaleWidth at the right edge. The default value of the ScaleLeft property is 0. ScaleMode The property ScaleMode determines the horizontal and vertical unit of measure for the coordinate system on a form or picture box. If the ScaleMode property of a form or picture box is set to 1 (the default), then the unit of measure become twips. Other possible values for ScaleMode are 2 for points (72 points = 1 inch), 3 for pixels, 4 for characters (1 horizontal unit = 120 twips; 1 vertical unit = 240 twips), 5 for inches, 6 for millimeters, and 7 for

centimeters. measure are ScaleWidth of an object

A value of 0 for the ScaleMode property indicates that units of to be determined from the current settings of the ScaleHeight and properties. Visual Basic automatically sets the ScaleMode property to 0 when any of the object’s Scale. . . properties are assigned values.

ScaleTop The property ScaleTop determines the vertical coordinate of the top edge of a form or picture box. After the statement objectName.ScaleTop = top is executed, the vertical coordinates range from top at the top edge of objectName to top + objectName.ScaleHeight at the bottom edge. The default value for the ScaleTop property is 0.

Appendix J — Visual Basic Statements

615

ScaleWidth The property ScaleWidth determines the horizontal scale on a form or picture box. After the statement objectName.ScaleWidth = wdth is executed, the horizontal coordinates range from objectName.ScaleLeft at the left edge of objectName to objectName.ScaleLeft + wdth at the right edge. The default value of the ScaleWidth property is the width of objectName when measured in the units specified by objectName’s ScaleMode property. Second The function Second extracts the seconds from a serial date. If d is any valid serial date, then the value of Second(d) is a whole number from 0 to 59 giving the seconds recorded as part of the date and time stored in d. [date]

Seek

See Appendix C.

Select Case

See Appendix C.

SendKeys The statement SendKeys a$ places in the keyboard buffer the characters and keystrokes specified by a$. The effect is exactly the same as if the user had typed the series of characters/keystrokes at the keyboard. The statement SendKeys a$, True places keystrokes in the keyboard buffer and waits until these keystrokes are processed (used) before allowing program execution to continue with the next statement in the procedure containing the SendKeys statement. Keystrokes can be specified which do not have a displayable character or which result from using the Shift, Ctrl, or Alt keys. See the Visual Basic reference manual or Help for further details. Set The statement Set objectVar = objectExpression associates the name objectVar with the object identified by objectExpression. For example, if the statements Dim

Scenery

AS

PictureBox

Set

Scenery

= picturel

are executed, then Scenery becomes another name for picturel, and references like Scenery.Print message$ are equivalent to picturel.Print message$. SetAttr

The statement SetAttr filename$, attribute sets the file attribute of the

file specified by filename$. A file’s attribute can be 0 for “Normal” or a combination of 1, 2, or 4 for “Read-only”, “Hidden”, and “System.” In addition, a file can

be marked as “changed since last backup” by adding 32 to its attribute. Thus, for example, if a file’s attribute is set to 35, (1+2+32)

then file is classified as a

Read-only Hidden file which has been changed since the last backup. SetFocus The method objectName.SetFocus moves the focus to the named form or control. Only the object with the focus can receive user input from the keyboard or the mouse. If objectName is a form, the form’s default control, if any, receives the focus. Disabled and invisible objects cannot receive the focus. If an attempt is made to set focus to a control which cannot receive the focus, the next control in tab order receives the focus. SetText

The

method ClipBoard.SetText info$ replaces the contents of the

clipboard with the string info$. Sen Shell

See Appendix C. See Appendix C.

Sin See Appendix C.

616

Appendix J — Visual Basic Statements

See Appendix C. While QBasic’s default variable type is Single, Visual

Single

Basic’s default variable type is variant. [variant]

See Appendix C.

Space$ Spe

See Appendix C.

Sqr

See Appendix C.

Static See Appendix C. In a procedure, arrays created by ReDim are lost when the procedure is exited. Arrays which are local to a procedure yet retained from one invocation of the procedure to the next can be created by dimensioning the array in the procedure with a Static statement rather than a ReDim statement. Dimensions for static arrays must be numeric constants. See Appendix C.

Stop

Str$ See Appendix C. StrComp The value of the function StrComp(a$, b$, compMode) is -1, 0, 1, or Null depending on whether a$ < b$, a$ = b$, af > b$, or either of a$ and b$ is

Null. The comparison will be case sensitive if compMode is 0 and case insensitive if compMode is 1. String

See Appendix C.

String$

See Appendix C.

Sub/End Sub Tab

See Appendix C.

See Appendix CG:

TabIndex The property TabIndex determines the order in which the tab key moves the focus about the objects on a form. Visual Basic automatically assigns successive tab indexes as new controls are created at design time. Visual Basic also automatically prevents two controls on the same form from having the same tab index by renumbering controls with higher tab indexes when the designer or program directly assigns a new tab index to a control. Tan

See Appendix C.

Text The property Text holds the information assigned to a text box. A statement of the form textBoxName. Text = a$ changes the contents of textBoxName to the string specified by a$. A statement of the form a$ = textBoxName.Text assigns the contents of textBoxName to af. TextHeight The value of the method objectName.TextHeight(strVar$) is the amount of vertical space required to display the contents of strVar$ using the font currently assigned for objectName. These contents may include multiple lines of text resulting from the use of carriage return/line feed pairs (Chr$(13) + Chr$(10)) in strVar$. The units of height are those specified by the ScaleMode and ScaleHeight properties of objectName (the default is twips). TextWidth

The value of the method objectName.TextWidth(strVar$)

is the

amount of horizontal space required to display the contents of strVar$ using the font currently assigned for objectName. When carriage return/line feed pairs (Chr$(13) + Chr$(10)) create multiple lines in serVar$, this will be the space required for the longest line.

Appendix J — Visual Basic Statements

Time$

See Appendix C.

Timer

See Appendix C.

TimeSerial

The value of the function TimeSerial(hour,minute,second)

617

is the

serial date corresponding to the given hour, minute, and second. Values from 0 (midnight) to 23 (11 P.M.) for hour, and 0 to 59 for both minute and second are normal, but any Integer value may be used. Often, numeric expressions are used for hour, minute, or second which evaluate to numbers outside these ranges. For example, TimeSerial(15—5, 20-30, 0) is the serial time 5 hours and 30 minutes before 3:20 P.M. TimeValue

The value of the function TimeValue(a$) is the serial date corre-

sponding to the time given in a$. TimeValue recognizes both the 24-hour and 12-hour time formats: “13:45:24” or “1:45:24PM”, .

Top The property Top determines the position of the top edge of a form or control. The units of measure are twips for forms. The units of measure for a control are determined by the ScaleMode property of the container (form, picture box, etc.) upon which the control has been placed, with the position of

the control measure from the edge of its container using the coordinate system established by the various Scale. . . properties for the container. By default, the unit of measure for a container is twips, with a value of 0 for the Top property placing the control against the top edge of the container. True A predefined constant whose value is —1. True is used when setting the value of properties that are either True or False. For example, Picture1.Fontltalic = True.

Type/End Type

See Appendix C. User-defined types may also include currency

or variant elements. [variant]

UBound

See Appendix C.

UCase$

See Appendix C.

Unlock

See Appendix C.

Val

See Appendix C.

Variant A variable of type variant can be assigned numbers, strings, and several other types of data. Variant variables are written without type declaration tags. [variant]

VarType The value of the function VarType(var) is a number indicating the type of value stored in var. This function is primarily used to check the type of data stored in a variant variable. The values returned by VarType are O for “Empty,” | for “Null,” 2 for Integer, 3 for Long Integer, 4 for Single Precision, 5

for Double Precision, 6 for Currency, 7 for Date, and 8 for String. [variant]

Visible The property Visible determines whether or not a form or control is displayed. If the Visible property of an object is True, then the object will be displayed (if not covered by other objects) and respond to events if its Enabled property is True. If the Visible property of an object is set to False, then the object will not be displayed and cannot respond to events.

618

Appendix J — Visual Basic Statements

WeekDay The value of the function WeekDay(d) is a number giving the day of the week for the date store in d. These values will range from 1 for Sunday to 7 for Saturday.

While/Wend

See Appendix C.

Width (Property) The property Width determines the horizontal size of an object. Width is measured in units of twips. For the Printer object, Width may be read (pw = Printer. Width is ok) but not assigned (Printer. an error).

Width = 100 causes

Width (Statement) Ifs is an integer less than 255 and n is the reference number of a file opened in sequential mode, then the statement Width #n,s causes Visual Basic to permit at most s characters to be printed on a single line in the file. Visual Basic will send a carriage return/line feed pair to the file after s characters have been printed on a line, even if the Print# or Write# statement would not otherwise start a new line at that point. The statement Width #n,0 specifies infinite width; that is, a carriage return/line feed pair will be sent to the printer only when requested by Print# or Write#.

WordWrap The WordWrap property of a label with AutoSize property set to True determines whether or not long captions will wrap. (When a label’s AutoSize property is False, word wrap always occurs, but the additional lines will not be visible if the label is not tall enough.) Assume a label’s AutoSize property is True. If its WordWrap property is set to True, then long captions will wrap to multiple lines, while if its WordWrap property is False (the default), then the caption will always occupy a single line. Ifa label has its WordWrap and AutoSize property set to True, then the label’s horizontal length is determined by its Width property, with long captions being accommodated by having the label expand vertically so that word wrap can spread the caption over several lines. If a label’s WordWrap property is set to False while its AutoSize property is True, then the label will be one line high and will expand or shrink horizontally to exactly accommodate its caption. Write#

See Appendix C.

Xor

(Logical Operator) See Appendix C.

Xor

(Bitwise Operator) See Appendix C.

Year The function Year extracts the year from a serial date. If d is any valid serial date, then the value of Year(d) is a whole number from 100 to 9999 giving the

year recorded as part of the date and time stored in d. [date]

Supporting Topics [color]: Numbers written in base 16 are referred to as hexadecimal numbers. They are written with the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A (=10), B (=11), C (=12), D (=13), E (=14), and F (=15). A hexadecimal number such as rst corresponds to the decimal integer t + 16*s + 162*r. Each color in Visual Basic is identified by a long integer (usually expressed as a hexadecimal number of the form GH. . .&) and referred to as an RGB color number. This number specifies the amounts of red, green, and blue combined to produce the color. The amount

of any color is a relative quantity, with 0 representing none of the color and 255 representing the maximum available. Thus black corresponds to 0 units each of

Appendix J — Visual Basic Statements

619

ted, green, and blue, while white corresponds to 255 units each of red, green,

and blue. The RGB color number corresponding to r units of red, g units of green, and b units of blue is r+256*g+65536*b, which is the value returned by the function RGB(r,g,b). Hexadecimal notation provides a fairly easy means of specifying RGB color numbers. If the amount of red desired is expressed as a two digit hexadecimal number, rr, the amount of green in hexadecimal as gg, and the amount of blue in hexadecimal as bb, then the RGB color number for this color is GHOObbggrr&. For example, the RGB color number for a bright green would come from 255 (FF in hexadecimal) units of green, so the RGB color number in hexadecimal is GHOOOOFFOO&.

[date]:

Functions dealing with dates and times use the type 7 variant data type.

Dates and times are stored as serial dates, double-precision numbers, with the

whole part recording the date and the decimal part recording the time. Valid whole parts range from —657434 to 2958465 which correspond to all days from January 1, 100 to December, 31, 9999. A whole part of 0 corresponds to December 30, 1899. All decimal parts are valid, with .0 corresponding to midnight, .25 corresponding to 6 a.m., .5 corresponding to noon, and so on. In general, the decimal equivalent of sec/86400 corresponds do sec seconds past midnight. If a given date corresponds to a negative whole part, then times on that day are obtained by adding a negative decimal part to the negative whole part. For example, October, 24, 1898, corresponds to a whole part of -432. A time of 6 p.m. corresponds to .75, so a time of 6 p.m. on 10/24/1898 corresponds to 432 + —.75 = 432.75. [variant]:

Variant is a new variable type that is not present in QBasic. Any

variable which is used without a type declaration tag ($, %, &, !, #, @) or without

being declared as a specific type using an As clause or a DefType statement is treated as a variant variable. A variable of type Variant can hold any type of data. When values are assigned to a variant variable, Visual Basic keeps track of the “type” of data which has been stored. Visual Basic recognizes 8 types of data: type O for “Empty” (nothing yet has been stored in the variable; the default), type 1 for “Null” (the special value Null has been assigned to the variable), type 2 for

Integer, type 3 for Long integer, type 4 for Single precision, type 5 for Double precision, type 6 for Currency, type 7 for Date/time, and type 8 for String. A single variant variable may be assigned different data types at different points in a program, although this is usually not a good programming technique. The data assigned to a variant array need not all be of the same type. As a result, a variant array can be used in much the same way as a user-defined type to store related data.

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3.

Disk Operating System

5. Untitled 9. Crrl+Y 13. Del 17. Shift+F5

7. 11. 15. 19.

A toggle key changes back and forth between two states. Backspace Home Cursor down

21.

23.

Ctrl+End

27. 31.

Vab Enter

35.

PgUp

Alt/F/X

DoMmESC 29.

Alt/F/N

33. 37.

Fl Alt/H/I or Alt/H/C

Exercises 1.3 CORY. 5. DIR 9. RD

3. RENAME 7. MD 11. NAME

CHAPTER Exercises 3.1 ih Ie te ON 2333333 13. 4E-08

3

17.

Valid

3.03125 fie ws 11. 3E+09 15. Valid 19. Not valid

Iles

10)

23-16

Dea

25.09 ZO

31

CUS

PRINT

> Guta}

PRINTO76

35.

CLS PRINT

17

*

(3

+

CLS LET xe= 95 +02.5 7" (9\ =" 3.25) DETeye=420-(7a/ (8)et oe) 4 Oey PRINT x / y

BOE

"(21 23)

xX Ay a) 2 6 11

116 ial

6

lig)

END

END

41.

* 20

CLS PRINTe

162)

END

37s

.055

END

END

33.

CEs

AS

ee

iil 7 | =

balance";

THEN

below

$150"

cost

627

Answers to Selected Odd-Numbered Exercises

628

43.

45.

REM Lottery

REM Convert to Pig Latin GES

CLS

LET

= 7)

(d3

= 7)

(d3

AND

= 7)

word$ "The

PRINT

THEN

+ "way"

= MID$(word$,

LEN(word$)

2,

- 1)

+ f$ + “ay"

word

in

pig

latin

is

";

word$

END

lucky$

PRINT

= word$

0 THEN

IF

END

ELSE (d2

f$)

LET

IF

IF

1)

ELSE

PRINT lucky$ END

f$ = LEFT$(word$, LET word$

THEN

word$

",

a word:

INSTR(“aeiou",

IF

= 7) OR

IF (d2

"Enter

INPUT

d3

d2,

= 7 THEN

dl

IF

dl,

",

seven"

= “Lucky

lucky$

LET

three

“Enter

INPUT

digits:

IF

END IF

END END

47.

REM Test if year is a leap year CLS MOD

((year

AND

4 = 0)

MOD

(year

IF

", year

a year:

“Enter

INPUT

PRINT

“This

is a leap year."

ELSE PRINT

“This

is not a leap year."

END

100

OR

0)

(year

MOD

400

= 0))

THEN

IF

END 49.

REM

of digits

number

Display

in a number

CLS a number

INPUT

"Enter

PRINT

“The number 1000

IF num >=

from

has

1 through

9999:

",

num

“;

THEN

"4 digits."

PRINT

ELSEIF num >= 100 THEN PRINT "3 digits." num >=

ELSEIF PRINT ELSE PRINT END

10 THEN

"2 digits." "1 digit."

IF

END

Exercises 4.3 he S05) 315

3.

5. Sorry, 1945. Work on the ENIAC began in June 1943. Correct. No, 1945. By then IBM had built a stored program computer. 9. Hi Hi 13. First CASE is executed even when num > 5, unclear Also, END SELECT is missing

17. Improper item in value list of second case 21. Valid 25. Invalid 29. SELECT CASE a CASE CASE

“one”

IS > 5

PRINT

END SELECT

7. The less things change, the more they remain the same. Less is more. Time keeps everything from happening at once. 11.

Needs a CASE clause before the PRINT statement.

15.

Error in second CASE. 30000

“two"

Should be CASE

10000 TO

19. Selector is a condition and cases are strings. 23. Invalid 27. Invalid 31. SELECT CASE a CASE

1

PRINT

Begins with a lowercase letter. Begins with an uppercase letter. Does not begin with a letter.

2

PRINT

CASE

"yes"

IS =< 5

PRINT

END SELECT

"no"

Answers to Selected Odd-Numbered Exercises

33.

REM Determine degree of cloudiness CLS INPUT

"Percentage

SELECT

CASE

of cloud

cover";

percent

percent

CASE

0 TO 30 PRINT "Clear"

CASE

31 TO 70

PRINT

"Partly

cloudy"

CASE

71 TO 99 PRINT "Cloudy" CASE 100 PRINT

CASE

"Overcast"

ELSE

PRINT

END

"Percentage

must

be

between

0 and

100."

SELECT

END

35.

REM Give number of days

in month

CLS

INPUT

"Enter

SELECT

CASE

a month

(do

not

abbreviate):

", month$

UCASE$(month$)

"FEBRUARY"

CASE

INPUT IF

"Is

it a leap year";

UCASE$(LEFT$(ans$,

LET

days

= 29

LET days

= 28

1))

ans$ = "Y"

THEN

ELSE END

CASE

"APRIL",

LET

CASE

days

"JUNE",

"SEPTEMBER",

"NOVEMBER"

= 30

"JANUARY",

LET

END

IF

days

"MARCH",

"MAY",

"JULY",

"AUGUST",

"OCTOBER",

"DECEMBER"

= 31

SELECT

PRINT

month$;

" has";

days;

"days."

END

37.

REM Give letter grade for number score CUS

39.

REM Determine cash award CLS

INPUT

"What

SELECT

CASE

CASE

is

score";

score

score

90 TO

CASE

Grade$

= "A" "B"

Grade$

CASE = "C"

LET Grade$ CASE

END PRINT END

END PRINT

END

= "Invalid"

SELECT "The

letter

grade

amount

75000 = .1 * amount 100000 = 7500

+

.05

*

(amount

- 75000)

amount

= 8750

+ .01

*

(amount

- 100000)

> 50000

LET amount IF

THEN

= 50000

END SELECT

= "F"

ELSE

LET GRADE$

amount

IF amount

IS 0 TO 59

recovered";

IS > 100000

LET

CASE 60 TO 69 LET Grade$ = "D" CASE

amount IS = 0) AND (celsius highest

THEN

highest

= num

number:

", num

* num

UNTIL

product

> 400

"The

highest

number was";

highest

END

close

all

doors."

IF

PRINT

LOOP

UNTIL

INPUT

(belt$

= "Y")

"How

many

gallons

"You

may

proceed."

AND

(doors$

of gas

are

= "Y") in

the

tank";

gas

PRINT PRINT

IF gas

< 2 THEN

PRINT

END

"Get

gas."

IF

END

REM Perfect squares

35.

CLS

REM Solve linear equation ELS

PRINT LET

"This

num

displays

the

perfect

squares

less

= 1

DO WHILE PRINT

LET

program

num num

num

than

100."

PRINT

"The

equation

is

ax

+ b = c"

PRINT

* num < 100

INPUT

* num

“Enter

the

values

of

a,

b,

solution

is

";

(c - b)

and

c:

IF a O THEN

= num + 1

PRINT

LOOP

"The

/a

ELSE IF b = c THEN

END

PRINT

“Every

number

is

a solution."

ELSE PRINT

END END

END

37.

",

REM Bounce a ball

and find total

distance traveled

CLS

ball"

PRINT

"

1)

tennis

PRINT

"

2)

basketball"

PRINT

“"

3)

super

PRINT

"

4)

softball"

ball"

PRINT

INPUT

"What

SELECT

CASE

CASE

type

of

ball";

bal]Num

1

LET

bounceFactor

=

.7

CASE 2 LET bounceFactor

=

.75

CASE 3 LET bounceFactor

=

.9

=

.3

CASE

4

LET

END

bal1Num

bounceFactor

SELECT

INPUT

"From

LET

height

LET

bounces

LET

distance

how many = height

meters * 100

= 1 = height

will

it drop"; ' convert

' first

height to

bounce

centimeters

IF

IF

"No

number

is a solution."

a,

400."

is highest."

IF

PRINT

IF doors$ END

numbers

DO

IF doors$

END

= 0

PRINT

IF

END

highest

LET product = 1 PRINT "Continue entering PRINT "The computer will

DO

33.

631

b,

c

632

Answers to Selected Odd-Numbered Exercises

bounces

LET

height

LET

distance

' up then

+ 2 * height

= distance

account

= 0

LET yrs

again

down

amt

",

in account:

amount

"Enter

INPUT

* bounceFactor

= height

savings

to deplete

Years

REM CLS

+ 1

= bounces

LET

39.

10

>=

* bounceFactor

height

DO WHILE

DO

LOOP "The

PRINT

USING

##.#

about

traveled

"and

"times

bounces;

bounced";

ball

PRINT

";

meters";

distance

/

100

LET

oldAmt

LET

amt

= amt -

1000

OR

(amt

1.05

*

= amt

CET yrse=synsital

END

never

will

"Account

PRINT

>= oldAmt)

THEN

oldAmt

>=

IF amt

=

1000000

PRINT

"years

are

yrs;

1980

age

+ age

= age

+

age

* age

1

LOOP

+, 1

LOOP UNTIL

= 1

age

END

required

to

reach

one

million

dollars."

END

45.

REM Greatest common divisor of two positive

integers

CLS INPUT

"Enter

DO WHILE LET

two

integers:

",

m,

n

n 0 t=n

LET

n =m

PET

im) ==

MOD

n

LOOP PRINT

m

END

Exercises 5.2 Ths 5.

413}

3.

Chicago New York le 3 8 5 —l 11. LOOP missing

I think I can. | think I can.

9. counters 13. EOD will be printed. 15.

REM

Find

largest

of a collection

of numbers

CLS

REM

Convert

"Enter largest

-1

when

finished."

PRINT

= 0

INPUT

INPUT

"Enter

a number:

IF num > largest LET LOOP PRINT END

to

kilometers

when

finished."

largest

",

num

"The

-1

"Enter

a distance

DO WHILE

THEN

LET

= num

PRINT

IF UNTIL

"Enter

PRINT

DO

END

miles

CLS

PRINT LET

17.

miles

kilometers

in miles:

-1

= 1.6

* miles

miles;

"miles

"Enter

a distance

is

equal

to";

kilometers;

PRINT num

= -1

largest

INPUT number

is";

largest

LOOP END

in miles:

",

miles

"kilometers."

Answers to Selected Odd-Numbered Exercises

19.

REM Report grades of eggs

21.

CLS

REM Translate doctors'

abbreviations

CLS

INPUT

"Weight

DO WHILE

of egg

ounces

in ounces";

ounces

INPUT

>= 0

< 1.5

THEN

PRINT

"Send

it to the

“ac. PRINT "before

bakery."

CASE

"The

SELECT

grade

CASE

CASE CASE

";

ounces

CASE

CASES

CASE

“at

Large"

CASE

"four

END

SELECT

times

a day"

ELSE

PRINT "Jumbo"

bedtime"

"qid"

PRINT

ELSE

PRINT

"hs"

CASE

"Extra

daily"

“a drop"

PRINT

ISt=

(-1

to stop):

",

score

0

> highest

THEN

LET

nextHighest

LET

highest

IF score LET

= highest

= score

INPUT LOOP

= totGrowth

growth

state,

California,

DATA

Illinois,

36.9, 13.5,

/ counter

for these

population

states

is";

aveGrowth;

21.4,

New

Florida,

13.0,

EOD,

York, 0

20.3

nextHighest

THEN

= score

IF "Enter

PRINT

"The

PRINT

"The next

END

in millions

Texas,

"percent."

> nextHighest

IF

END

"percent."

growth;

by";

pop2010

DATA END

a score

score

+ growth

grew

population

average

Data:

= 0

ELSE

state$,

"The

= 0

"Enter

END

aveGrowth ---

nextHighest

IF score

LOOP PRINT

LET

"EOD"

PRINT READ

highest

DO WHILE

= counter

totGrowth

PRINT

LET

INPUT

pop2010

PRINT

LET

REM Report two highest scores

a score

highest

(-1

score

to highest

to stop): is";

",

score

highest

score

is";

nextHighest

633

634

29.

Answers to Selected Odd-Numbered Exercises

their

and

parentheses

Remove

REM

contents

from

a sentence

31.

CLS

available

liquids

Display

REM

sent$

"Sentence"; = 0

parensFlag

letter$

SELECT

= MID$(sent$,

CASE

CASES

PRINT

"You

position,

1)

END

LET parensFlag LET

CASE

= 0

REM

ELSE

THEN

liquid$

IF

---

DATA

IF parensFlag PRINT

= 0 THEN

DATA:

price

Apple

liquid,

Cider,

DATA Gasoline,

letter$;

DATA

IF

Pancake

cost

2.60,

1.30, Syrup,

per

Beer,

gallon

6.00,

SELECT

LET

position

= position

2.30,

Gatorade,

15.50,

Spring

Water,

+ 1

LOOP END

.202 is a zero

Exercises 5.3

Sy

Pass # 1 # 2

Pass

# 3

Pass

# 4

8

7

9.

13.

17.

21.

3.

BO

20

tn

a

1

4

7

6

2

5

8

11

6

9

12

a5

oDDDD

7.

2

4

6

3:46.31

SteverScottum

3-016

Mary

4:20.5

Slaney

11,

***...****Hooray***. ..****

15.

Temperature

Density

AAAAA

40

62.423

TTTTT

45

62.419

AAAAA

50

62.409

55 60 65

62.39 62.198 62

1000 Kilo 1000 Kilo 1000000

mega

1000000

mega

1.0E+09

giga

1.0E+09

giga

1.0E+12

tera

1.0E+12

tera

1.0E+15

peta

1.0E+15

peta

Improper nesting of loops

19,

For without Next

23.

FOR num = 1 to 10 STEP 2 PRINT NEXT

25.

8 Who do we appreciate?

Steve Cram

REM Display a row of ten stars CLS FOR

END

num

num

REM Display

10 x 10 array of stars

CLS i

= 1

PRINT NEXT

27.

“**;

FOR

i

= 1 TO

FOR

j = 1 TO 10

PRINT

ul

NEXT

j

PRINT NEXT

END

10

i

ae

Bleach,

Milk,

END

END

Pass

following:"

Loop

parensFlag

END

36

THEN

LET

x = 72

Deflection"

FOR

i = 1709

NEXT

6

payments

made:

",

n

= prin

Balance

LET

interest:

of

=

* Balance

(1 + r / 1200)

- pmt

7

"The

amount

still

owed

is";

Balance

END -d

IF

PETEME= PRINT NEXT

Balance

PRINT

LET

END

LET

(inches) "

(inches)

d = 0 TO

"

Maximum

from

pmt

ate SOR(S)

hp Sex USING

"—

##

Re. (ee

(2a =

2)

e277

ed

Ht #Htt";

ds;

es

ED)

M

d

END

CHAPTER

6

Exercises 6.1 1.

kilogram is the unit of mass in the metric system.

3.

5.

Least said, soonest mended. Source: Fortune cookie. 30% of M&M’s Plain Chocolate Candies are brown.

7.

9. 13.

It was the best of times. It was the worst of times.

11. 15.

Divorced, beheaded, died; Divorced, beheaded, survived.

144 items in a gross The time required for a population to double in size is 34.65736 years. Your name has 7 letters. The first letter is G

Answers to Selected Odd-Numbered Exercises

7

You look dashing in blue

19.

7is\be The molarity of the salt water solution is Zo. abcde atk

M = nmoles / volume = .5 25. The number of members of the U.S. Senate is 100 Zo:

Sle Gabriel, in the year 2000 your age will be 20 3S). Your will receive a BS degree at age 22 39. A string parameter is missing in the subprogram.

33. Sk 41.

43.

45.

REM

Display

a lucky

number

CLS

M

1000000

milli

m

-001

Unicorn

168 hours in a week 76 trombones in the big parade The Statue of Liberty weighs 250 tons All’s well that ends well. Since Print is a keyword, it cannot be used as the name of a subprogram. REM

Courses

CLS

LET

num

CALL

= 7

CALL

PrintInfo("Civil

Lucky (num)

CALL

PrintInfo("Mathematics",

END Lucky

REM

SUB PrintInfo

(num)

Display

PRINT

num;

message "is

END

SUB

REM

Undergraduate

a lucky

majors

number."

at

U of MD,

College

Park

49.

"Analysis

of Structures")

“Calculus")

enrolled)

Majors(major$,

CALL

enrolled

READ major$, ---

REM

Data:

computer

DATA

SUB

REM

Return

the

(major$,

Display

"In

1992,

PRINT

enrolled;

", word$

and

its

length

LEN(word$)

enrolled)

major

PRINT

of a word

SUB Length (word$) REM Output the word

556

economics,

914,

science,

enrolled

of students

number

major,

PRINT word$; END SUB

REM

"; major$

END

END

Majors

length

of

enrolled)

Majors(major$,

CALL

END

subject$)

" is a subject

CLS INPUT "Enter a word: CALL Length(word$)

enrolled

READ major$,

(major$,

subject$;

PRINT

CLS

SUB

Engineering",

END

SUB

47.

mega

information

the

University

of Maryland

“undergraduate

";

major$;

had"; " majors."

END SUB

51.

637

REM

Display

the

average

of

three

53.

numbers

REM

Years

and

days

old

CLS

CLS "Enter

INPUT

CALL

",

numbers:

three

Average(first,

second,

first,

second,

third)

END

third

INPUT

“What

is your

year

CALL

ShowYears (birthYr)

CALL

ShowDays (birthYr)

of

birth";

birthYr

END SUB

Average

REM

Display

second,

(first, the

END SUB

"The

SUB ShowDays

average

LET ave = (first PRINT

third)

average

+ second is";

+ third) ave

/ 3

REM

Display

PRINT

"You

PRINT

(1994

(birthYr) age have

in days lived

for

- birthYr)

more

* 365;

than";

"days."

END SUB SUB

ShowYears

REM

Display

PRINT

END

SUB

"You

(birthYr) age

are

in years

now";

1994

- birthYr;

“years

old."

Answers to Selected Odd-Numbered Exercises

638

55.

in courses

Enrollments

REM

CLS "In

PRINT

READ CALL

READ CALL REM

students, course$ ShowEnrolled(students,

course$)

students, course$ ShowEnrolled(students,

course$)

---

Data:

number

Spanish,

533600,

DATA

1990,"

year

the

of

students

enrolled,

course

French

272600,

END SUB

ShowEnrolled

REM

course$)

Display

enrollment

and

PRINT

USING

"###,###";

students;

PRINT

“ college

END

57.

(students,

students

course

took

a course

in

";

course$

SUB

REM Display speeds of waves CLS

CALL

PrintSpeed("light",

3E+08)

CALL

PrintSpeed("sound",

360)

END

SUB

PrintSpeed

PRINT END

59.

(wave$,

"The

speed

of

speed) ";

wave$;

“ is";

speed;

“meters

per

second."

SUB

REM Display WOW vertically

61.

CLS

REM Compute tips for services

rendered

CLS

CALL

DrawW

INPUT

"Enter

the

person's

CALL

Draw0

INPUT

"Enter

the

amount

CALL

DrawW

INPUT

"Enter

the

percentage

END

CALL

Tip(job$,

occupation: of

the

bill,

percent)

bill,

percent)

bill:

tip:

",

END

SUB

Draw0

REM

Draw

PRINT

"

PRINT

"|

the

letter

SUB

eee XT

**

PRINT PRINT

0

"

Display

ae

LET

total

cats

PRINT

“Tip

PRINT

USING

eee

SUB

DrawW

END

SUB

REM

Draw

the

PRINT

"**

PRINT

3" **

PRINT

"

PRINT

"

(job$,

REM

PRINT END

Tip

letter

the

tip

= bill the

* percent ";

/ 100

job$;

"$$##.##";

total

SUB

W

EASE as

Kk **

kK

ORK **H

PRINT

END

SUB

Exercises 6.2 1

9

3.. ‘Can'Can

By

75)

7.

9. Approximate Annual Wage: 20000 13. NE io Ci

11. 15. 19.

35

Dim. A) | 25. DATA cannot be in a subprogram.

The number is

1,234.57

Gabriel was born in the year 1980 Buckeyes Hello Ray and Bob and Bob

23

discovered Florida

", ",

job$ bill

percent

Answers to Selected Odd-Numbered Exercises

Zi.

REM Calculate

sales

29:

tax

CLS

InputPrice(price)

CALL Compute(price, CALL

tax,

ShowData(price,

cost)

tax,

cost)

END

Compute

(price,

tax,

REM

Calculate

the

LET

tax

* price

LET

cost

SUB

=

.05

= price

InputPrice

REM

Get

INPUT

InputName(name$)

CALL

GetFirst(first$,

CALL

ShowLetter(first$)

cost + tax

price

of

"Enter

the

price

SUB

SUB

ShowData

REM

(price)

the

END

(price,

Display

name$)

PRINT

"Tax:

PRINT

"----------- J

PRINTS

"Costs

REM

Convert

",

";

LET

n = INSTR(name$,

LET

first$

InputName

cost)

"3; tax

full

"What

SUB

SUB

ShowLetter

PRINTS

tDear

PRINT

"We

name

is your

END

price

n - 1)

(name$)

Input

INPUT

" ")

= LEFT$(name$,

SUB

price

name

first

Extract

REM

item:

name$)

REM

SUB

item

of the

(first$,

END

bill

“Price:

SUB

the

tax,

PRINT

END

full

name";

name$

(first$) is

are

ahinstSsw

proud

ss

to

accept

you

to

Gotham

END SUB

“sicost

feet

and

inches

to

centimeters

CLS

33;

REM

Calculate

meal

cost

CLS

CALL

InputLngth(feet,

CALL

Convert(centimeters,

CALL

ShowSize(centimeters)

inches)

feet,

inches)

END

CALL

InputBil} (subTotal)

CALL

Compute(subTotal,

CALL

ShowData(subTotal,

tip, tip,

total) total)

END

SUB

Convert

(centimeters,

REM

Convert

to

LET

totalInches

= 12

LET

centimeters

= 2.54

feet,

SUB Compute

inches)

SUB

Input

(feet,

length

total

+ inches

LET

tip

* subTotal

* totalInches

LET

total

the

in feet

INPUT

"Number

of feet";

INPUT

“Number

of

SUB

length

and in

inches";

inches

=

.15

tip

= subTotal

feet

and

InputBill

REM inches."

feet

+ tip

Display "The

(centimeters) size length

in in

Input

INPUT

the

"Enter

END

SUB

SUB

ShowData

REM

ShowSize

(bill) price the

of

the meal

price

of

the

meal:

inches

SUB

SUB

and

the

inches)

"Give

PRINT

total)

Calculate

* feet

PRINT

REM

tip,

END SUB

InputLngth

REM

(subTotal,

REM

centimeters

END SUB

END

acceptance

CALL

SUB GetFirst

cost)

END SUB

SUB

of

END

SUB

END

Letter

CLS

CALL

31.

REM

centimeters centimeters

is";

centimeters

(subTotal,

Display

tip,

charges

PRINT

"Subtotal:";

subtotal

PRINT

"

tp

PRINT

"----------- «

PRINT

2)

END

SUB

ips

Total: ss total

total)

",

bill

College."

639

Answers to Selected Odd-Numbered Exercises

640

35.

3

percentage markup

REM Calculate

REM

Calculate

batting

average

CALL

ReadStats(name$,

atBats,

CALL

ComputeAverage(atBats,

CALL

DisplayInfo(name$,

DATA

Sheffield,

CLS

CLS

CALL

InputAmounts(cost,

CALL

ComputeMarkup(cost,

CALL

DisplayMarkup (markup)

price)

markup)

price,

END

557,

hits) hits,

ave)

hits,

ave)

ave)

184

END

SUB ComputeMarkup (cost, price, markup) LET markup = 100 * ((price - cost) / cost)

SUB ComputeAverage

LET

SUB

END

SUB DisplayMarkup PRINT

"The

SUB

SUB

DisplayInfo

markup

InputAmounts

is";

markup;

(cost,

"percent."

"Enter

the

cost:

",

INPUT

“Enter

the

selling

cost price:

",

PRINT

name$,

PRINT

USING

“.###";

ave

END

SUB

Rack

mall

comparison

table

CLS CALL

DisplayHeader

FORM

= 1 10\3

CALL

ReadInfo(mall$,

CALL

ComputeRent(rentPerFoot,

CALL

DisplayInfo(mall$,

NEXT

i

REM

---

DATA

Data:

Green

mall,

Mall,

rentPerFoot,

squareFeet)

squareFeet,

rentPerFoot,

rent

per

6.50,

583,

(rent,

feet,

foot, Red

rent)

squareFeet,

square

Mall,

rent)

feet

7.25,

426,

Blue

Mall,

5.00,

823

END SUB

ComputeRent

REM

Compute

LET

total

total

rent

= rent

total)

given

rent/foot

and

number

of

feet

* feet

END SUB SUB

DisplayHeader

PRINT

"Mall

Name

Rent

per

Square

Foot

Total

Feet

Monthly

Rent"

END SUB SUB

DisplayInfo

(mall$,

rentPerFoot,

\

S$tt tt

LET a$ = "\ PRINT

USING

a$;

mall$;

rentPerFoot;

squareFeet,

ReadInfo

READ

END SUB

mall$,

(mall$,

rentPerFoot,

rentPerFoot,

squareFeet;

squareFeet)

squareFeet

rent)

HHT

END SUB

SUB

"Batting

Average"

SUB

ReadStats

(name$,

atBats,

atBats,

hits

price

END

Hat

ave)

"Name",

READ

Display

(name$,

PRINT

price)

INPUT

REM

/ atBats

(markup)

END SUB

59:

= hits

END

END SUB SUB

ave

(atBats,

rent

SH, tee

ee"

SUB

name$,

hits)

641

Answers to Selected Odd-Numbered Exercises

41.

REM Display equation

of a line

43.

CUS CALL

GetCoefficients(c,

d,

CALL

DisplayEquation(c,

d, e)

e)

END

REM Raise a complex

number to the nth power

CLS CALL CALL

GetData(n, ReX, ImX) ComputeAnswer(n, ReX,

CALL

ShowResult(ReY,

ImX,

ReY,

ImY)

ImX,

ReY,

ImY)

ImY)

END

SUB

DisplayEquation

REM

Display

PRINT

the

"The

(c,

d,

e)

equation

in

equation

of

the

the

form

line

is:

x = a or

y= mx

+ b

SUB

";

LET

ReY

= Rex

LET

ImY

=

FOR

i

IF d = 0 THEN BRUNT

exe

ELSEIF

="

sen

ComputeAnswer

C

e / d < 0 THEN

END END

MultiplyComplex(ReX,

LET ye

suse—

Gu) dXa

ImX ImX,

ReY,

ImY,

ReZ,

ImZ)

BBE

ELSE BRUNT

ReX,

= 2 7T0n

CALL

PRINT "y ="; -c / ds "x -"3 ABS(e / d)

(n,

seemed

NEXT

IF

END

ImY

=

ImZ

7

SUB

SUB

SUB GetData SUB

GetCoefficients

REM Get PRINT DO

(c,

coefficients "The

WHILE

= 0)

e)

of the

equation (c

d,

of

AND

a (d

equation

line

in

of a line

standard

form

in standard is

cx

+ dy

form = e"

= 0)

INPUT

"Enter

the

value

of

the

coefficient

c:

",

c

INPUT

"Enter

the

value

of

the

coefficient

d:

",

d

INPUT

"Enter

the

value

of the

coefficient

e:

",

e

ReX,

"Enter

a positive

INPUT

"Enter

real

INPUT

"Enter

imaginary

SUB

SUB

MultiplyComplex

SUB

Imx)

INPUT

END

LOOP END

(n,

number:

part

",

of a complex part

(ReX,

of

ImX,

ReY,

Perform

LET

ReZ

= ReX

* ReY

-

ImX

*

LET

ImZ

= ReX

*

+

ImX

* ReY

END

ImY,

multiplication:

ImY

",

Rex

number:

ReZ,

",

ImX

ImZ)

Z = x * Y

ImY

SUB

SUB ShowResult

(ReY,

PRINT

"Real

PRINT

"Imaginary

END

number:

a complex

REM

complex

n

ImY)

part

of power:"; part

of

ReY

power:";

ImY

SUB

Exercises 6.3 1935 3. The population will double in 24 years. 5. The function value is .5 7. You can park about 500 cars. 9. The day is Wed 11. train 13. moral has the negative amoral 15. Missing $ sign at end of Greeting. political has the negative apolitical 17. Twice should be a numeric function, and no argument should be given in the assignment of Twice. 19.

REM Convert

Celsius

to Fahrenheit

21.

CLS

REM Round a positive number m to n decimal CLS

CALL

InputTemp(t)

CALL

InputData(m,

CALL

ShowNewTemp(t)

CALL

RoundIt(m,

END

REM

CtoF

Calculate

Fahrenheit

temperature

from

Celsius END

END

FUNCTION

SUB

InputTemp INPUT

“Enter

a temperature

in Celsius:

",

t

ShowNewTemp SUB

t;

"Enter

a positive

INPUT

"Round

it to how many decimal

"degrees

Celsius

is";

CtoF(t);

"degrees

number

to

round:

",

places";

m

n

SUB

REM

(t)

n)

(m,

INPUT

(m,

Rounded

FUNCTION

(t)

Round

a number LOUA

LETEYS=

Mie

Rounded

= INT

SUB

PRINT

END

n)

InputData

SUB

(t)

CtoF = (9 / 5) * t + 32

SUB

n)

END

FUNCTION

END

places

END

FUNCTION

SUB

RoundIt

(r)

n) to a given neta.

number

of decimal

places

5

/ (10 * n)

Fahrenheit" PRINT END

SUB

m;

(m,

n)

“rounded

to";

n;

"places

is";

Rounded(m,

n)

642

23.

Answers to Selected Odd-Numbered Exercises

25.

REM Popcorn Profits CLS CALL

InputAmounts(popCost,

CALL

ShowProfit(popCost,

REM Cost of airmail cLS

butterCost, butterCost,

bucketCost, bucketCost,

price) price)

CALL

InputWeight (weight)

CALL

ShowCost (weight)

END

END

SUB

InputAmounts

(popCost,

butterCost,

bucketCost,

INPUT

"What

is the

cost

of the

popcorn

kernels";

INPUT

"What

is

the

cost

of the

butter";

butterCost

INPUT

"What

is

the

cost

of the

bucket";

bucketCost

INPUT

“What

is the

sale

price";

price

Ceil = -INT(-x) END FUNCTION

END SUB

FUNCTION

Profit

(popCost,

REM Calculate

Profit

END

the

= price

butterCost,

profit

bucketCost,

on a bucket

- (popCost

SUB

InputWeight

profit

"The

PRINT

butterCost,

of an airmail

letter

- 1)

bucketCost,

(weight) of

the

letter

in

(weight) cost of mailing

the

letter

is";

weight

the

"Enter

INPUT

(popCost,

cost

the

+ bucketCost)

FUNCTION

SUB ShowProfit

(weight)

Cost = .05 + .10 * Ceil(weight END FUNCTION

price)

of popcorn

+ butterCost

Cost

Calculate

REM FUNCTION

up

Round

REM

popCost

(x)

Ceil

FUNCTION

price)

",

ounces:

END SUB

price)

is";

PRINT Profit(popCost, END SUB

butterCost,

bucketCost,

price)

SUB ShowCost PRINT "The

Cost(weight)

END SUB 27.

REM

Display

CLS INPUT

a greeting

for

a senator

29.

REM

Determine

the

senator's

name:

"; name$

DIM

PRINT PRINT

“The Honorable

"; name$

PRINT

"United

Senate”

PRINT

"Washington,

States

count(1

of Stirling

approximation

TO 3)

FOR n = 1 TO 34 LET f = Factorial (n) LET s = Stirling(n)

DC 20001"

IF ABS(s

PRINT

PRINT

accuracy

CLS “Enter

- f)

/ f
b) AND Largest

sp a

primes

CET n=

= primes

+ 1

"; c is"; Largest(a,

b,

c)

a,

b,

and c

(a > c) THEN

= c

Largest

IF

END END

= b

IF

FUNCTION

= primes

FUNCTION

FUNCTION Atan2 REM

(y, x)

Returns

the

37.

value

of the

standard

position

angle

in radians

REM Convert from meters to feet and vice versa

LET pi

= 4 * ATN(1)

OS INPUT

SELECT

CASE

x

INPUT

"Enter

IS > 0

PRINT

"Length

CASE

Atan2 = ATN(y / x) CASE CASE

= SGN(y)

END

the

input

the

length

* pi

/ 2

FUNCTION IF

= ATN(y

/ x) + SGN(y)

Convert

Convert END

REM Display Arccos(x)

41.

>=

(x

-1)

x;

“Arccos(";

AND

")

the

in

a number

"Enter

=";

(x

0 THEN

END

CASE

unit:

is";

length)

THEN

IF

MySGN

CASE

"M"

FUNCTION MySGN

DO

FUNCTION

(inUnit$,

FUNCTION

IF

CLS

PRINT

unit

ELSE END

UNTIL

=

Convert

FUNCTION

LOOP

(M or F):

in that

in the other

inUnit$

* pi

SELECT

INPUT

unit

END

IS < 0

Atan2 END

"Enter

0

Atan2

39.

number

b

ELSE

LOOP

END

number:

";

ELSEIF c > b THEN

ni / F

NumberOfPrimes

number:

=a

Largest

LET

"; a

FUNCTION Largest (a, b, c) REM Find largest number among

ELSE

END

largest

number:

in n

f 0 THEN

MA

35.

643

IF FUNCTION

= 0

",

inUnit$

",

length

Convert(inUnit$,

length)

Answers to Selected Odd-Numbered Exercises

644

43.

an

to

due

interest

Calculate

REM

45.

of a number

representation

Binary

REM

balance

unpaid

GES

CLS INPUT

"Enter

PRINT

"The

num

",

integer:

an

representation

binary

is

";

Binary$(num)

"Enter

PRINT

"Interest

Interest (balance)

$";

is

balance

",

balance:

unpaid

INPUT END

END

Calculate

REM

= ""

a$

LET

LOOP END

.015

be

paid

* balance

- 1000)

* .01

FUNCTION

END

IF

= num \ 2

UNTIL

Binary$

THEN

to

END IF

LET a$ = "1" + a$ LET num

1000

interest

of

= 15 + (balance

Interest

ELSE END

amount

ESE

+ a$

"0"

=

a$

LET

the =

Interest

2 = 0 THEN

IF num MOD

4). 17. elect$(1) elect$(2) elect$(3)

21.

11. 15. 19,

Array subscript out of range (eventually). Improper syntax in DIM statement. a) Apr Sep b) Dec,Jan,Feb

23.

REM

Calculate

Replace lines 11 through 17 with: REM

Display

name

LET

highest

= 0

LET

sum

= 0

FOR

i

8

FOR

i

2 10.9

=

110

of

the

student

with

the

highest

NEXT

END

PRINT

=

LET

IF

sum

the

sum

STEP

of odd

indexed

"The

sum

of

the

odd

indexed

entries

name$(i)

PRINT IF

END

i

NEXT

REM Compare arrays a$() LET

differFlag

FOR

i = 1 TO 10

IF

a$(i)

LET END NEXT

and b$()

for same values

= 0

t

=

110

b$(i)

THEN

differFlag

NEXT

7

12

LET grades(i)

= grades(i)

+ 7

i

= 1

i

IF differFlag

= 1 THEN

PRINT

"The

arrays

are

"The

arrays

have

REM

Curve

FOR

i

=

grades 1 TO

not

identical."

identical

values.”

NEXT

i

by adding

5 percent

12

LET grades(i)

ELSE IF

REM Curve grades by adding FOR

IF

PRINT

27.

array

i

THEN

= highest

IF score(i)

in

= sum + a(i)

= 11708

i

entries

2

i

FOR

END

score

IF score(i) > highest THEN LET highest = score(i) NEXT

25.

NOMS 14

watt

volt

ohm

|

coulomb

elect$(4)

Stuhldreher Crowley

= (1.05)

* grades(i)

is";

sum

a()

Answers to Selected Odd-Numbered Exercises

29.

REM Array m() stores the same numbers as array n(), REM

but with

DIM r(1 FOR

no duplications

TO 50)

i = 1 TO

LET

100

n(n),

NEXT

31.

= 1

REM Create and display the frequency of scores BES DIM

frequency(1

REM

Set

LET

count

FOR

i = 1 TO

= 0

IF r(i) END

50 = count

+ 1

DIM m(1

TO count)

LET

index

FOR

i

IF

1 TO

r(i) LET

m(index)

LET

index

END NEXT

scores

in each

of

five

intervals

= 1 TO 30

score

LET

frequency(range)

= INT(score

/ 10)

+ 1

‘Number

= frequency(range)

in

=

i

= index

+ 1

IF

Display

frequency

"Interval

LET

a$

FOR

interval

=

"##

PRINT

7

NEXT

DATA

to

in each

##

+ 1

interval

5

a$;10*(interval

- 1),10*in frequency (interval terv al, )

interval

---

Data:

10,

5, 4,

arbitrary

25, LU,

23,

list

45,

46,

125230, l/s

lOse

of

49,

scores

47,

315) 40545, Sal

4 el oce

2,

44

205,21 Zed

teelO)

END

REM Inventory processing

35.

CLS REM

Read

TO

5),

item

FOR bin

sold(1

costs

REM

Compute

PRINT

and

"Bin

LET

af

LET

totalRev

and

5),

amtLeft(1

quantities

TO 5)

sold

sold(bin) display

Quantity

and

remaining

revenue

Revenue"

## = 0

Het ##" ‘Total

LET

totalRev

PRINT

= 45

revenue

+ revenue

bin;

amtLeft(bin);

revenue

"Total

"The

PRINT

revenue:

bin

following

";

totalRev

bins

contain

PRINT

END

DATA’ END

fewer

than

20

";

items:

= 1 TO 5

IF amtLeft(bin)

REM

i =

< 20 THEN

bin;

IF bin

---

Data:

3-005,

105.

item

into

the

array

messages

in

1 TO 8 STEP

two

lines

2

messages$(i);

" "3;

7

cost,

12.255,-30,

sold

quantity

37-45,

95

i = 1 TO 8 STEP

NEXT

i

REM

---

END

PRINT

NEXT

FOR

DATA

PRINT

FOR

Print

PRINT

bin

PRINT

messages

REM

FOR

* cost(bin)

= totalRev a$;

i = 1708

NEXT

- sold(bin)

= sold(bin)

USING

FOR

TO 8)

PRINT

LET amtLeft(bin) revenue

Read

PRINT

= 1 T0 5

LET

REM

in two lines

READ messages$(i) NEXT i

inventory

= " #

FOR bin

NEXT

TO

REM Place messages CLS DIM messages$(1

= 1 T0 5

READ cost(bin), NEXT bin

1-5

##"

= 1 T0

DATATIO SS Gs

cost(1

of

Frequency"

USING

DATA135)

DIM

range

PRINT

REM

33.

the

dataElement

PRINT

1 THEN

= 0

count

range

REM 50

=

scores,

LET NEXT

= 1

=

Read

READ

i

to 0

= 1 T0 5

FOR dataElement

IF

NEXT

elements

range

REM

count

TO 5)

frequency(range)

NEXT

= 1 THEN

LET

array

FOR range

i

LET

645

7.49542,

24.95,

17

messages$(i Data:

This,

It,

2 + 1);

" "3

messages is,

seems,

a,

you,

test,

passed

Answers to Selected Odd-Numbered Exercises

646

#7.

Histogram

Distribution

Frequency

REM

CLS DIM

frequency(1

REM

Read

READ

vel

TO 6)

-1

vel

DO WHILE

measurements

velocity

missile

- 500)

= INT((vel

LET

index%

LET

frequency(index%)

+ 1

/ 100)

+ 1

= frequency(index%)

vel

READ

LOOP Display

FOR

i = 1 T0 6 + 100 * i + 99;

frequency(i)

j = 1 TO

FOR

"3; 400 + 100 * i; 400

- ####

"####

USING

PRINT

frequencies

with

histogram

REM

22 tts

PRINT. j

NEXT

frequency(i)

PRINT

NEXT

i

REM

---

measurements

Data:

, 750, 1020 980,660, 850,1010,930,880,970,960 970,890,970,900, 1030,950,1000,940,970,600,-1

DATA DATA END

Exercises 7.2 1. No.

3. 7.

Michigan less than greater than equals less than Total rainfall for the 1st quarter is 10 Parameter should be planet$() in the CALL statement and subprogram.

5.

The sum of the first 4 elements is 30

9.

South Pacific

11.

Duplicate DIM statement in subprogram.

15.

17. nis set | too high 21. Array subscript will be out of range when i = 5.

19.

hue$ will be unknown in the subprogram.

23.

25.

REM Determine

13.

SUB CopyArray REM

Place

FOR

i

=

1

(a(), a's

values

to

UBOUND(a)

BET sbi) NEXT END

b()) in

b

="a i)

LET

order

FOR

i

=

=

if array is ascending 1

1 TO

49

IF scores(i)

i

LET

SUB

END NEXT

> scores(i

order

+ 1)

THEN

= 0

IF 1

IF order PRINT

= 1 THEN "Array

is

ascending"

“Array

is

not

ELSE PRINT

END 27.

REM

Determine

LET

ascend

LET

descend

FOR

i = 1 TO 49

if order

=

ELSEIF LET END NEXT

IF

ascending,

both,

=

1

> scores(i

ascend

+ 1)

THEN

= 0

scores(i) descend

< scores(i

+ 1)

THEN

= 0

IF i

(ascend

= 1)

PRINT

"Array

ELSEIF PRINT

ELSEIF PRINT

(ascend "Array

(ascend

AND

(descend

is

both

= 0) is

ascending

AND

neither

= 1)

= 1)

(descend

PRINT IF

THEN and

THEN

"Array

is ascending"

"Array

is descending"

descending"

= 0)

ascending

ELSE END

descending,

1

IF scores(i) LET

is

THEN

nor

descending"

or

neither

IF

ascending"

647

Answers to Selected Odd-Numbered Exercises

29.

REM

Merge

DIM

c(1

LET

indexA

= 1

LET

indexB

= 1

LET

doneA

= 0

LET

LET

doneB

= 0

DO WHILE

FOR

i = 1 TO 40

IF

ascending

arrays,

with

31.

duplications

SUB FindMinMax

TO 40)

c(i)

max

THEN

LET max

= k2

ENDIF = 1

doneB

LET

LET

IF

n =n+2

LOOP

IF n = UBOUND(arrayVar)

i

NEXT

IF

+ 1

ELSE

END

THEN

= kl

IF kl < min END

< 20 THEN indexB

+ 1)

IF

ELSE LET c(i)

+ 1)

LET kl = k2 LET k2 = temp

+ 1

ELSE LET

n < UBOUND(arrayVar)

LET k2 = arrayVar(n) IF arrayVar(n) < arrayVar(n

= a(indexA)

LET

END IF

array

inv=r2

LET

IF indexA

END

of a large

values

LET min = arrayVar(1) LET max = arrayVar(1)

((a(indexA) LET

min, max)

maximum

and

minimum

Find

REM

(arrayVar(),

IF arrayVar(n) LET min ELSEIF

END

< min

THEN

= arrayVar(n)

arrayVar(n)

LET max END

THEN

> max

THEN

= arrayVar(n)

IF

IF

END SUB

33.

REM

Maintain

a list

DIM state$(1 LET

ans

LET

count

of

35.

states

TO 3)

= 0 ans

Report

PRINT

4

students

scoring

above

class

average

num)

Ave(grades(),

num);

"students

scored

above

the

average"

END

PRINT

"1)

Enter

PRINT

"2)

Delete

PRINT

"3)

Display

PRINT

"4)

Quit"

a State" FUNCTION

a State" the

States"

PRINT

INPUT

"Please

SELECT

CASE

CASE

(grades(),

Compute

the

LET

sum

= 0

LET

tot

= 0

FOR

i = 1 TO num

NEXT

count)

IF

count)

0 THEN

LET

count)

classAve

IF

FOR

i = 1 TO num

IF grades(i) EET

END END

INPUT (Hai

"Enter

NEXT

count)

a state

the

from

a State

Ave

list

to Delete:

", name$

a} ceat

DO WHILE Wi

(i

at Seat

< count)

(name$

AND

> state$(i))

seal

LOOP

(name$

state$(i))

PRINT

"State

does

INPUT

"Press

ENTER

OR not

= sum / num

END

LOOP

Delete

number

EUSE

SELECT

REM

and

7 num

3

(state$(),

average

LET classAve

CALL Display(state$(),

Del

num)

LET sum = sum + grades(i)

1

CASE

Ave

REM

ans

CALL Del(state$(),

END

ans

",

1-4:

enter

CALL Enter(state$(), CASE 2

IF

of

PRINT

ELS

SUB

number

DIM grades(1 TO 100) CALL InputGrades(grades(),

= 0

DO WHILE

REM

(count

= 0)

THEN

exist"

to continue.",

dummy

END

IF i

= tot

FUNCTION

tote=

= 0

> classAve tote

tat

THEN

of

students

above

it

648

Answers to Selected Odd-Numbered Exercises

ELSE

"Shuffle

LET

count

FOR

k = 7 TO

LET

rest

= count

-

array

down

by

= state$(k

+ 1)

the

grades,

LET

num

LET

grd

list

IF grd LET

state$(i)

-1)

-1

num

AND

END

= num

+ 1

IF

LOOP

PRINT

"Press

ENTER

to

Continue.",

dummy

END SUB

END SUB

REM

(state$(),

Enter

a new

IF count

count)

state

in

the

= UBOUND(state$)

correct

position

already

been

THEN

PRINT

"Fifty

states

INPUT

"Press

ENTER

"Enter

a State:

have

to

continue.",

entered."

dummy

ELSE INPUT

state$(count EN

+ 1)

",

name$

= name$

eon

DO WHILE WP

state$(i)

Ul

< name$

eS ay axe al

LOOP

IF

(name$

= state$(i))

AND

PRINT

"State

already

INPUT

"Press

ENTER

ELSE

' Shuffle

FOR

j

(i previousNumber

ELSEIF

INPUT

finish):

= number

descend

LET

to

= number

number

(-1

AND

(descend

to

finish):

",

number

LOOP IF

(ascend

= 0)

PRINT

"Sequence

ELSEIF

(ascend

PRINT

is

= 0)

THEN

neither"

= 1)

THEN

"Sequence

is

"Sequence

is descending"

ascending"

ELSE PRINT

END

IF

END

43.

FUNCTION

ScalarProduct

REM

Compute

the

LET

product

= 0

FOR

i = 17T0n

LET NEXT

scalar

q(),

45.

n)

product

of p()

and

q()

REM

Read

product

+ p(i)

substance$(1), highest

FOR

index

READ

7

FUNCTION

PRINT END

Convert

test

range(1

TO

score

to

letter

grade

CLS

DIM

13),

letter$(1

ReadData(range(),

CALL

InputScore(score)

CALL

ShowGrade(range(),

REM

---

Data:

87,

A-,

score)

grades

(000-07.

Ct5)7450C.)

DAVAR/ 748

letter

90,

A,

94,

13)

letter$(),

ranges,

At,

97,

DATA

TO

letter$())

CALL

B,

Bt,

84,

Dt,

0045.

80,

B-

60551D=51.05

oF

END

(score)

InputScore

SUB

number

Input

REM

END

SUB

SUB

ReadData

FOR

i = 1 TO

NEXT

converted:

",

score

scores

to

letter

grades

13

range(i),

READ

converted

letter$())

linking

data

Read

be

to

(range(),

REM

be

to

score

score

“Enter

INPUT

letter$(i)

7

END

SUB

SUB

ShowGrade

REM

Convert

LET

index

DO WHILE LET

LOOP PRINT END SUB

to

score

letter

grade)

grade

= 1

range(index)

index

“The

letter$(),

(range(),

=

index

letter

> grade + 1

grade

boiling

for this

score

is

“;

letter$(index)

SUB

points.

boilingPoint(1)

= 1 = 2 T0 8

substance$(index), LET

NEXT

REM

and

IF boilingPoint(index)

= product

END

49.

substances

LET

* q(i)

boilingPoint())

(substance$(),

SUB Display READ

product

ScalarProduct

END

(p(),

highest

boilingPoint (index)

> boilingPoint(highest)

= index

IF

index

substance$(highest),

boilingPoint (highest)

THEN

649

Answers to Selected Odd-Numbered Exercises

650

Exercises 7.3 100 1. 200 5. Variables being swapped are not of the same type. 9.

4 swaps

13.

5 swaps

17.

Determine the number of times that each of the four integers occurs and then list the determined number of 1s, followed by the determined number of 2s, etc.

21.

REM

Insertion

DIM

b$(1

READ

Assume

Sort.

are

items

100

stored

in

DATA

7 Numbers interchanged. 11 3. 7. Sequential se ao, 2 Il aE GA) Maks Gav 15. 12 comparisons. 19. 16; 84; 5

statements.

100)

to

b$(1)

FOR

i

= 2 TO

100

23.

READ temp$ LET k=i-1

Keak

(temp$

< b$(k))

temp

LET

x=

= x y

LET y = temp

= b$(k)

+ 1)

LET b$(k LET

AND

(k > 1)

DO WHILE

LET

of x and y

the values

REM Interchange

1.

LOOP

IF (k = 1) AND (temp$ < b$(1)) LET b$(k + 1) = b$(k) VET

END

ke=nka=

THEN

1

IF

LET b$(k NEXT

i

REM

---

+ 1)

Data

= temp$

statements

go

here

END 27.

REM

Input

array

of measurements

and

determine

GES

median

29.

REM

Determine

number

of

occurences

CLS

CALL DIM

their

InputNumberOfMeasurements (n) nums(1

TO

n)

DIM

nums(1

TO 200)

DIM

dist(0

TO

63)

CALL InputNums (nums ()) CALL DisplayMedian(nums () )

CALL FillArray(nums()) CALL GetOccurrences(nums(),

END

CALL

dist())

ShowDistribution(dist())

END

SUB

DisplayMedian

(nums())

REM Display the median PRINT "The median is";

of the

n measurements

Median(nums())

END SUB

SUB

FillArray

(nums())

REM Generate

numbers

LET nums(1) FOR

SUB

InputNumberOfMeasurements

REM

Input

INPUT END

number

"Number

(n)

of measurements

of measurements";

= 2 TO

LET

nums(i)

NEXT n

0 to 63

and

- 1)

+ 7)

place

in

= 5 200

= (9 * nums(i

MOD

64

i

END SUB

SUB

SUB

SUB InputNums (nums()) REM Input list of measurements

FOR i = 1 TO UBOUND(nums) INPUT “Enter number: ", nums(i) NEXT

END

i

from

i

GetOccurrences

(nums(),

REM Record occurrences FOR i = 1 TO 200

LET dist(nums(i)) NEXT i END

SUB

SUB

ShowDistribution

dist())

for each

number

= dist(nums(i))

+ 1

SUB

REM

Display

(dist())

distribution

array

FOR

i = 1 TO 63 PRINT USING "## NEXT i END SUB

##

Se

wis) dist (iye

array

Answers to Selected Odd-Numbered Exercises

FUNCTION

CALL

Median

(nums())

SortNums (nums () ) n = UBOUND(nums)

LET

IF INT(n

/ 2)

= n / 2 THEN

'n is even

LETm=n/2 LET med

= (nums(m)

+ nums(m

ELSE

'n

LET med END

= nums((n

+ 1)

is

/ 2 odd

/ 2)

IF

Median

END

+ 1))

= med

FUNCTION

SUB SortNums REM

(nums())

Bubble

sort

list

of

numbers

LET n = UBOUND(nums) FORi=1T0n-1 FOR

j =

1 T0n

IF nums(j)

NEXT NEXT END

31.

i

> nums(j

SWAP END

-

nums(j),

+ 1)

THEN

nums(j

+ 1)

IF j

7

SUB

REM Translate an American word to English

33.

CLS

REM Compute average of five highest test scores CLS

DIM

american$(1

CALL

TO 12), english$(1 TO 12) ReadWords(american$(), english$())

CALL

InputData(name$,

CALL

InputWord(word$)

CALL

SortData(score())

CALL

FindWord(word$,

CALL

ShowData(score(),

---

REM

attic,

DATA

flashlight,

DATA

ice

DATA

sneakers,

chips,

loud

hailer,

megaphone,

ice,

cream,

fries,

lorrie,

truck,

plimsolls,

gasoline,

zero,

radio,

petrol

wireless

INPUT

“Student's

Perform

LET

foundFlag

LET

first:

LET

last

DO WHILE

= 1

= 12

(first

CASE

NEXT

= 0)

SUB

SUB

ShowData

LET

sum

FOR

passNum

END

first

+ 1

= middle

REM

Bubble

FOR

passNum

(score(),

name$)

= 1 TO

5

sum / 5

= 1 THEN

"The

English word

word

is

is

not

";

listed"

english$(middle)

END

NEXT

END SUB

IF

SUB

SUB

InputWord

(word$) word

"Word

to

index

(score()) sort

scores

in descending

order

= 1 TO 6 = 1 TO

7 - passNum

IF score(index) < score(index + 1) THEN SWAP score(index), score(index + 1) NEXT

END

SUB

score(i)

SUB

FOR

"The

PRINT

END

score";

passNum

SUB SortData

- 1

ESE

INPUT

name$

= 0

PRINT name$,

SELECT

Input

scores

LET sum = sum + score(passNum) NEXT

ELSE

PRINT

REM

"Test

END

/ 2)

= 1

= middle

last

foundFlag

END

test

7

LOOP IF

name";

seven

IS > word$

LET END

+ last)

= INT((first

foundFlag

LET CASE

(foundFlag

AND

last)

name$)

(search$

OPEN

filename$

(NOT

filename$) #1

AS

INPUT

FOR

AND

(NOT

EOF (1))

copies

title$,

#1,

INPUT

searchTitle$)

(title$

WHILE

DO

EOF(1))

year

name$,

#1,

INPUT

InputData(searchTitle$,

LET title$ = ""

LET name$ = "" WHILE

CALL

LOOP

LOOP

IF name$

“ is

search$;

PRINT

(searchTitle$, filename$) REM Input book name and determine file INPUT “Title of book"; searchTitle$

name

copies

IF

END

#1

CLOSE

#1

listed."

not

is

"Book

PRINT

in YOB.DAT"

not

IF

CLOSE

is",

ELSE

BUSE END

inventory

in

copies

of

"Number

PRINT

- year

1994

is";

age

"'s

name$;

PRINT

THEN

= searchTitle$

IF title$

THEN

= search$

END

END

InputData

SUB

(H or P)";

or Paperback

“Hardback

INPUT

bookType$

IF bookType$ = "H" THEN LET

filename$

= "HARDBACK. INV"

filename$

=

ELSE LET END

"PAPERBCK.INV"

IF

END

SUB

REM

Add

Exercises 8.2 1.

to

AVERAGE.DAT

Create

REM

hold

batting

3.

averages

the

end

"AVERAGE.DAT"

FOR

APPEND

the

file

AVERAGE.DAT

CLS

CLS

“Enter

INPUT

"Player";

WHILE

DO

to end

EOD

PRINT

name$

OUTPUT

FOR

"AVERAGE.DAT"

OPEN

AS

OPEN

#1

input"

“Enter

INPUT

"Player";

name$

0,

name$,

WRITE

#1,

INPUT

"Player";

"Initialize

0

counters

name$

name$

WHILE

DO

"EOD"

end

to

EOD

PRINT

AS

#1

update”

name$

"EOD"

0,

name$,

WRITE

#1,

INPUT

"Player";

0

name$

LOOP

LOOP CLOSE

#1

CLOSE

#1

END

END

17.

of

to

players

Split the file into two or more files which can be stored in arrays, sort these files using arrays, and then merge them.

CHAPTER Exercises 9.1 1. Pacific Mississipp

9

3.

heights are same 170 eye colors are same

5.

Variables used in LET statements invalid.

9.

astrology.nom and astrology.sign. NUMBER is an invalid data type.

11.

TYPE planet planetName TYPE

7.

AS

STRING

AS

* 20

SINGLE

Reserved word “name” used as field name and no END

TYPE statement. 13.

distanceFromSun END

Should be

TYPE car make

AS

model year

AS AS

mileage

END

TYPE

STRING

* 20

STRING SINGLE

AS

SINGLE

* 20

Answers to Selected Odd-Numbered Exercises

15.

REM

Input

three

words

and

display

them

in

first

three

655

zones

CLS DIM namel DIM name2

AS STRING AS STRING

* 14

DIM

AS

* 14

name3

* 14

STRING

INPUT

"Input

name

1";

namel

INPUT

"Input

name

2";

name2

INPUT

“Input

name

3";

name3

PRINT

namel;

name2;

name3

END

Exercises 9.2

1. VA

ci

5. Virginia Tech Harvard

VA

1872

MA

1636

IDA WI VA 3 7. Milwaukee Area Tech. Col.

9. Cannot take length of a variable type. Should be

WI

11.

Cannot PRINT record variable.

15.

REM Make random file YOB2.DAT

1912

LEN (actor). 13.

TYPE typeNums numl

AS SINGLE

CLS

num2

AS

SINGLE

TYPE

num3

AS

SINGLE

DIM

STRING

* 15

yr AS SINGLE

numbers

OPEN

file YOB.DAT

typePerson

nom AS

END TYPE

from sequential

AS

typeNums

"NUMBERS.DAT"

FOR

RANDOM

AS

#1

LEN

= LEN(numbers)

END

TYPE

DIM

person

AS

typePerson

OPEN

"YOB.DAT"

OPEN

"YOB2.DAT"

LET

recNum

DO WHILE

=

NOT

FOR

INPUT

AS #1

FOR RANDOM

AS #2

LEN

= LEN(person)

1

EOF(1)

INPUT #1, name$, year LET person.nom = name$ LET

person.yr

PUT

#2,

LET

recNum

= year

recNum,

person

= recNum

+

1

LOOP CLOSE CLOSE END

CHAPTER

#1 #2

10

Exercises 10.2 1. 5.

WINDOW REM

(-1,

-5)-(7, and

axes

Draw

SCREEN

2

WINDOW

(-2,

LINE

(-2,

LINE LINE

(0, (3,

30)

Sh 7.

line

"For -40)-(12, 0)-(12,

VGA

(3,

CIRCLE

(10,

SCREEN

12

240)

0)

‘Draw

-40)-(0, 240) 200)-(10, 150)

CIRCLE

use

x-axis

150),

"Draw y-axis "Draw line

REM

LINE

40)

"y-axis

REM

(0,

-8)-(0,

SCREEN

2

WINDOWS

(=52° (G2)

line

and

axes

Draw

"For VGA 9450-02)

4545

* 7S)

O)a(1-25~

(450-3)

CIRGUER

.05

use SCREEN 2d

12

ml ecevar.5)

94, 10) tee

"Draw

+ 355)

a circle

Draw

2

WINDOW

(-10,

CIRCLE

(0,

0),

in

center

the

"For

VGA

-10)-(10,

10)

4

use

of

the

SCREEN

screen

12

11.

REM

Draw

2 (-10,

SCREEN WINDOW LINE

(-10,

LINE

(0,

LINE

(1,

END:

a tick

5ure0S at

mark

70

on

‘For VGA use -10)-(100, 100)

the y-axis

SCREEN

0)

"x-axis

-10)-(0,

100)

"y-axis

70)-(-1,

70)

0)-(100,

x-axis

‘Draw y-axis ‘Draw line

END

SCREEN

END

‘x-axis

its (0, ao Ses LINE (2, .5)-(4, 3) CIRCEEN(Zs6-5)ian 03

END 9.

0)

DINE

.05

200),

(hile (El, MeGs

12

Answers to Selected Odd-Numbered Exercises

656

13.

REM

corners

four

in the

points

Draw

is

19:

WINDOW

(0,

0)-(10,

10)

10) 2.5)

STEP

=9.5

FORD

LINE

(0,

LINE

(5,

LINE

(5,

0)-(0, 5)-(5,

5) 5)

5)-(5, 0)-(0,

0) 0)

2

WINDOW

(0,

1 10)

0)-(6,

(6,

12

SCREEN

10)

0)-(10, 5)

use

VGA

‘For

SCREEN

line

and a tangent

REM Draw a circle

LINE END

r

NEXT

(0,

CIRGHEN(539

0 And

rate!

> 0 Then

Picturel.Print

DoubleYears(amount!,

Picture2.Print

MillionYears(amount!,

End

Let Textl.Text

= Val(Text1l.Text)

If amount!

= "Centigrade"

= "Convert

661

rate!) rate!)

If

Sub

= "Fahrenheit"

= "Convert

to Centigrade"

Function

If

Sub

DoubleYears!

Let

bal!

Let

years!

Do

(a!,

r!)

= a!

While

= 0

bal!

Let

bal!

Let

years!

< 2 * a!

= (1 +r!)

* bal!

= years!

+

1

Loop

End

Function

Function

MillionYears!

Let

bal!

Let

years!

Do While

(a!,

r!)

= a! = 0

bal!

Let

bal!

Let

years!

=

< 1000000 (1 + r!)

* bal!

= years!

+

1

Loop

End

Object

Property

Form]

Caption Alignment Caption

Labell Text Command1 Label2

Function

Setting Stamps 1 — Right Justify Number of Sheets of Paper

(blank)

Caption Alignment Caption

Determine Stamps Required 1 — Right Justify Number of stamps

Picture Sub

Command1

Let If

Click

stamps!

()

= Val(Textl.Text)

stamps!

>

Int(stamps!)

/ 5

Then

Int(stamps!)

stamps!

+ 1

Picturel.Cls Picturel.Print End

stamps!

Sub

PresidentialT

Object Form] Labell

Property Caption Caption

Setting Presidential Trivia Last name of one of the four most recent Presidents

Textl Text

Command! Picture! Sub Commandi Click ( ) Let pres$ = Textl.Text

Select Case UCase$(pres$) Case

Is

= "CARTER"

= "Georgia"

Let

state$

Let

trivia$

= "The

Let

trivia$

= trivia$

Case

Is

state$

Let

trivia$

Let

Is

soft

+ "White

in

served

drink

House

was

the

Carter

Coca-Cola."

= "REAGAN"

Let Case

only

= "California" = "His

secret

service

code

name

was

Rawhide."

= "BUSH"

state$

Let trivia$

= "Texas"

= "He was

the third

left-handed

president."

"

Alignment (blank) Caption

1 — Right Justify

Ok

Answers to Selected Odd-Numbered Exercises

662

Case

Is = "CLINTON"

Let state$ Let

End

= "Arkansas" = "In

trivia$

imitation

a good

he did

college

of

Elvis

Presley.”

Select

Picturel.Cls

Picturel.Print Picturel.Print

"President " + pres$ + "'s"; " home state was "+ state$ + "."

Picturel.Print Let Textl.Text

trivia$ = ""

Text1.SetFocus End

Sub

Sub

Commandl Click

Let Textl.Text End

Object Form1 Labell

Property Caption Caption Alignment

Textl Text Command!

(blank) Caption

Command2

Caption

()

= UCase$(Text1.Text)

Sub

Sub Command2 Click () Let sentence$ = Textl.Text Let End

Textl.Text

= CapFirst$(sentence$)

Sub

Function CapFirst$

(a$)

Let af = af

+ """

Let

= ""

result$

Do While Rem

‘cause ‘initial

Rtrim$(a$)

Find

end

of next

input

string

variable

to end

to hold

in a space

converted

sentence

"" word

(include

all

trailing

spaces)

Let place! = InStr(a$, " ") Do While Mid$(a$, place! +1, 1) =" " Let place! = place! + 1 Loop Rem Record next word and remove it from a$ Let word$ = Left(a$, place!) Let a$ = Mid$(a$, place! + 1) Rem

Capitalize

first

letter,

make

Let word$ = UCase$(Left$(word$, Rem Add word to results Let result$ = result$ + word$

sure

1))

other

letters

are

+ LCase$(Mid$(word$,

lowercase

2))

Loop

Let CapFirst$ End

result$

Function

Exercises 12.4 1. Goodbye

5,

1 2 3

9. The event procedure Command1_Click does not allow parameters. 11. Cannot have a string variable named num$ if you already have a single-precision variable named num!. 13.

The reserved word name cannot be used as a variable.

15. The Swap statement is not supported in Visual Basic; use Let temp = num1: Let num1 = num2: Let num2 = temp.

3.

$1,234.57

Setting Capitalization Sentence 1 — Right Justify Capitalize GEntire Sentence Capitalize GFirst Letter of Each Word

Answers to Selected Odd-Numbered Exercises

Wie

Picturel.Print

Format$(3.52*1000000000000,

"Currency")

(Note: 1 trillion is 1 followed by 12 zeros.)

a Nes

Let

Picturel.ScaleMode

Let

Picturel.CurrentX

= 2

‘Third

column

Let

Picturel.CurrentY

= 1

"Second

row

(first

using

units

Picturel.Print

23%

"Visual

Let

Picturel.ScaleMode

Let

Picturel.CurrentY

Picturel.Print

Let

sign$

Let

a$

MsgBox

Zo:

= 4

‘Position

=

1

"display

on

=

.5

‘display

half

a$,

can't

steal

, "Taking

is your second

Risks

Let Printer.FontBold Printer.Print

units

of characters

(first

column row

is

is 0) 0)

2nd

of characters

row

way

between

lst

& 2nd

row

zodiac

base

and

sign?") keep

one

foot

on

first."

Proverb"

= True

Sule

"Hello"

Let

Temp$

Let

Textl.Text

= Textl.Text

Let Text2.Text

33%

"#,#")

"4"

= InputBox$("What

= "You

using

Format$(2*10,

Basic"

Picturel.CurrentY

Let

‘Position

Picturel.Print

"x";

Picturel.Print

Weis Zi.

= 4

19.

ReDim a$(1975 To 1994)

35.

= Text2.Text

= Temp$

In the declarations section of (general) place the statement Dim nom$

Bile

Dim marx$(1

To 4)

‘in declaration

section

of

(general)

39.

Picturel.FontName Picturel.Print

Sub

41.

"S"

)

Form _Load( Let marx$(1)

= "Chico"

Let marx$(2)

= "Harpo"

Let marx$(3)

= "Groucho"

Let marx$(4)

= "Zeppo"

End

= "Symbol"

Sub

Picturel.DrawWidth

= 3

Picturel.Scale

4)-(10,

(0,

-4)

Picturel.Line

(1,

0)-(9,

0)

Picturel.Line

(9,

0)-(8,

2)

Picturel.Line

(9,

0)-(8,

-2)

Picturel.CurrentX

= 1

Picturel.Currenty

= -.1

Picturel.Print

"EAST"

Object Labell

Property Alignment Caption

Setting 1 — Right Justify How many quarters do you have?

Textl Command1

Text Caption

(blank) Display Dollars and Cents

Object Labell

Property Alignment Caption

Setting 1 — Right Justify Letter

Text 1

Text

(blank)

Label2

Alignment Caption

1 — Right Justify Number

Text2

Text

(blank)

Command!

Caption

Display Number as Subscript of Letter

Picturel Sub

Command1

Click

()

Picturel.Cls Picturel

Print

Picturel.Print End

Textl.Text

Format$(.25

+ " quarters

is";

* Val(Textl.Text),

"currency")

Sub

Picture

663

Answers to Selected Odd-Numbered Exercises

664

Sub

Commandl

Click

()

‘character

= 4

Picturel.ScaleMode

units

Picturel.Cls

Picturel.Print

Textl.Text;

Picturel.CurrentY Picturel.Print

End

= Picturel.CurrentY

+

.3

Text2.Text

Sub

Object Labell

- 1. Street Address

~ | =| od al

Property Alignment Caption

Setting 1 — Right Justify Name

City, State. Zip Code

r

Text]

Text

(blank)

Pica| eee eee

Alignment Caption Text Alignment Caption

1 — Right Justify Street Address (blank) 1 — Right Justify City, State, Zip Code

Text3

Text

(blank)

Command!

Caption

Print Letterhead

Label2 Text2

Label3

Sub

Command1

Rem

The

Click

number

() 93

was

chosen

Printer.ScaleMode

= 4

‘characters

Printer.CurrentX Printer.Print

& error

- Len(Textl.Text))

/ 2

=

(93

- Len(Text2.Text))

/ 2

- Len(Text3.Text))

/ 2

Text2.Text

Printer.CurrentX Printer.Print

(93

trial

Textl.Text

Printer.CurrentX Printer.Print

=

by

=

(93

Text3.Text

Printer.EndDoc

End

Sub

Object Picture Command!

Dim

instance!

‘in declaration

Sub Command1 Click If

instance! Let

section

instance!

=

1

Command1.Caption instance!

Picturel.Circle

End End

If

Sub

(general)

= 0 Then

= "Draw

-10) a Bigger

Else Let

Caption

()

Picturel.Scale (-10, 10)-(10, Picturel.Circle (0, 0), 1 Let

of

Property

= instance!

(0,

0),

+ 1

instance!

Circle"

__ Setting Draw Circle

Answers to Selected Odd-Numbered Exercises

J

An eres

beset

Object

Property

Setting

Text Text2 Command!

Text Text Caption FontSize Caption 12 Caption FontSize

(blank) (blank) F 12 -

Command2 FontSize Command3

Command4 Labell Picturel Label2 Command1

Sub

()

Click

Picturel.Cls

Picturel.Print End

Sub

Sub

Command2

+ Val(Text2.Text)

Val(Textl.Text)

Click

()

Picturel.Clis

Picturel.Print End

- Val (Text2.Text)

Val(Textl.Text)

Sub

()

Sub Command3 Click Picturel.Cls

Picturel.Print End

Sub

Sub

Command4

* Val(Text2.Text)

Val(Textl.Text)

Click

()

Picturel.Cls

Let

denom!

If denom! MsgBox

= Val(Text2.Text) = 0 Then "Division

by

zero

is

not

possible"

Else Picturel.Print

End If End Sub

Val(Textl.Text)

/ denom!

FontSize Caption

x 12 = Symbol 12 =

Caption

Enter numbers, then select operation to perform

Caption FontName

665

Index

! single-precision tag, 84 # format character, 94

# double-precision tag, 84 $ format character, 95

$ string tag, 53 % integer tag, 84 & long integer tag, 84 ’ for remark, 68

* multiplication operator, 40 \ \ / _ 4

format character, 96 integer division operator, 85 exponentiation operator, 40 format character, 99 to 3 ratio rule, 414

search of ordered, 288 shuffling of elements, 431 sorting, 305 static, 549 two-dimensional, 323, 345 variable, 272

ASC function, 59, 520 Ascending order, 287 ASCII table, 55, 515-516, 569 table display, 59 value, 55, 515-516

Breakpoint, 551, 596 removing and setting, 552, 595-596 Bricklin, Dan, 25 Bubble sort, 305, 307,345

flagged, 371 Bug, 29, 550 Button, Tom, 26 Byron, Augusta Ada, 22 CALL statement, 208, 521

Capitalization, 45, 214

Asterisk, 40 Asymptote, graphing vertical, 420 Atanasoff, John V., 23 AIN function, 80, 520

Caps Lock key, 7 Caption property, 466, 511, 598

Absolute value, 79 Accelerator keys, 580 Access key, 465

AutoRedraw property, 489, 597

Accumulator, 167, 171, 201 Addition, 40 Aiken, Howard, 23

BackColor property, 468, 512, 597-598 Background color, 415 Backslash, 96

CASE clause, 132, 541 Ceiling function, 91, 251 Chart flowchart, 31 hierarchy, 33

ABS function, 79, 520

Algebraic function, 79 Algorithm, 4, 29 merge, 290 Newton-Raphson, 206 Alignment property, 466, 511, 597 Allen, Paul, 25 Alt key, 8, 11, 13 AND logical operator, 112 Apostrophe, 70 Appending to a file, 358

Babbage, Charles, 22

Backspace key, 6, 13, 558

BackStyle property, 468, 598 Backus, John, 24 Bar menu, 5, 11 status, 5, 6

Arctangent, 80

title, 5 Bardeen, John, 24 Barnaby, Robert, 26 Base in exponentiation, 46 Base of a file name, 17 BASIC, 4 Binary file, 549 Binary search, 293, 313, 345 Binomial coefficient, 243

Argument, 212 Arithmetic operation, 40, 105

Bisection method, 173 Block of text, 559

Array, 272, 346

Body FOR...NEXT loop, 185

Arccosecant, 86 Arccosine, 86

Arccotangent, 86 Arcsecant, 86 Arcsine, 86

determining range, 294 dimension, 273

dynamic, 549

main, 209 Bohm, Corrado, 24

key field, 317 ordered, 287

Boole, George, 22

parallel, 278

Box model, 206 Branching, 256 Brattain, Walter, 24 Break, 372

passing, 291 range, 273, 276

removing, 278

BorderStyle property, 468, 512, 598

Caret, 40 Carriage return, 44

top-down, 31, 33

Checkbook case study, 502-511 Check-out receipt, 377 CHR$ function, 55, 521 Circle method, 493, 512, 598 CIRCLE statement, 413, 426, 521

Clearing a program from memory, 560, 567 Clipboard, 561, 568, 586 CLOSE statement, 358, 522

Closing a file, 357 Cls method, 472, 512, 599 CLS statement, 9, 522 Coding a program, 29 COLOR statement, 415, 522 Command button, 462, 465, 583 Common logarithm, 86 Comparison, 112 Compiler, 24 Complex numbers

addition and display, 136 nth root, 149, 226 Concatenation, 54 Condition, 112, 117, 147, 152 Confusing IF block, 121 Constant numeric, 40, 104 string, 53, 104

667

668

Index

Control character, 59 variable, 186, 201, 372 Control break processing, 371 Control variable, 186, 201, 372 Cooper, Alan, 26 Coordinate axes, drawing, 411

Coordinate systems, 409, 548 COPY command (DOS), 19 Copying text, 561, 586 COS function, 523 Cosecant, 86 Cosine, 80 Cotangent, 86 Coulomb’s law, 250 Counter, 167, 171 Counter variable, 288

Ctrl key, 7 Ctrl+End key, 11 Ctrl+Home key, 11 Currency, 486, 599

CurrentX property, 486, 495, 512, 599 CurrentY property, 486, 495, 512, 599 Cursor, 5

Cursor Down key, 13

Diskette, 2, 15

DOS, 4 drive, 2 QBasic, 4 Displaying a procedure, 214, 562, 593 Divide and conquer method, 34 Division, 40 DO loop, 152, 200, 524 Documentation, 30, 67-68, 70

Dollar sign, 53, 95

DOS 7 DOUBLE identifier in DIM, 396 Double-precision, 84, 85, 396

Debugging, 23, 29, 433, 550ff, 563-564, 595-596 Decision structure, 34 DECLARE statement, 215, 523 DEF FN statement, 83, 524

Default drive, 17 value, 46, 546 Del key, 7, 13, 558 Deleting a breakpoint, 552, 596 DeMorgan’s laws, 115 Derivative of a function, 175

Descending order, 287 Design modular, 214, 254-256 top-down, 214, 234, 254-256 Desk-checking, 38, 550 Dialog box, 9, 21, 581ff

(QB), 569-570 (VB), 588 Differential equations, graphing solutions to, 422 Dijkstra, Edsger W., 24 DIM statement, 273, 324, 393, 524 Dimension of an array, 273 DIR command (DOS), 19

Directory, 17, 546-547 root, 17, 583 subdirectory, 17 Direct-access file, 401 Disk, 17

Exiting QBasic, 11 Exiting Visual Basic, 584 EXP function, 79, 526 Exponent, 41, 46

Exponential function, 79 Exponentiation, 40 Expression, 105

numeric, 43

string, 54

Double-subscripted variable, 323

Extension of a file name, 17

Dragging mouse, 576 DrawStyle property, 493, 602 DrawWidth property, 495, 512, 602 Driver, 258 Dynamic array, 549

Fl key, 11 F2 key, 214 F4 key, 10

Eckert, J. Presper, 23 Editing commands, 558, 567-568,

586-587 Editor, 6 smart, 12 using (QB), 561, 567-568 Efficiency of sorts, 311 Element, 272 ELSE clause, 117, 132 Empty string, 58 END FUNCTION, 242 END IE 117 End key, 7, 13, 558 End of data, 167 END SELECT, 132

Notepad, 492

data, 17 direct-access, 401 length, 401

END statement, 525 End statement, 478, 489,

END SUB, 208 END TYPE, 393 EndDoc method, 488, 602 Ending Windows, 583 Enter a line, 12 Enter key, 8, 13 Environment, 561ff EOD (End Of Data), 167 EOF function, 359, 362, 526

ERASE command (DOS), 19 ERASE statement, 278 190

illegal function call, 85 NEXT without FOR, 190 out of data, 69 subscript out of range, 278 syntax, 10, 45, 69 Esc key, 5, 8, 13 Euler’s method, 421

Event trapping, 549

F6 key, 550 F7 key, 552 F8 key, 552 F9 key, 552 F10 key, 552 Faggin, Federico, 25 Field, 94, 392

binary, 549 closing, 357 creating with Windows’

ELSEIF clause, 120

Error, 10 FOR without NEXT,

F5 key, 552, 596

length, 392 File, 17

using (VB), 586-587

DATA statement, 63, 214, 523 Data file, 17

Event procedures, 472 Events, Visual Basic, 471ff Execute, 9 to cursor, 552

merging, 370 name, 17, 20, 356, 382 opening for append, 358 opening for input, 359 opening for output, 357 random-access, 361, 399, 405,

548-549 reading from, 359 reference number of, 356, 382 relative, 401

sequential, 356 sorting, 368-369 writing to, 357 Filespec, 18, 20, 362, 382, 547 FillColor property, 493, 603

FillStyle property, 493, 603 FIX function, 82, 527 Fixed-length string, 390-391, 405 Flag, 167, 171, 201

Flagged bubble sort, 317 Flowchart, 31, 257

Flowline, 31 Focus, 465 FontBold property, 468, 512, 603 Fontltalic property, 468, 512, 603

Index

FontSize property, 463, 511, 604 FOR...NEXT loop, 185, 201, 527 body, 185 control variable, 186, 201 initial value, 185

terminating value, 185 FOR without NEXT error, 190 ForeColor property, 463, 512, 605 Form, 461

design, 590-591

Format$, 485, 512, 605-607 Form_Load event, 506 FORMAT command (DOS), 18

Format string, 94 Frequency table, 277 Function, 78, 103, 242ff, 527-528 ABS, 79, 520 algebraic, 79 ASC, 59, 520 ATN, 80, 520 ceiling, 91, 251

CHR$,55, 521 COS; 0; 523) derivative of a, 175

EOE 359, 362, 526 EXP=79; 526 exponential, 79 FIX, 82, 527 graph of a, 418ff

Games of chance, 436ff

Integration, 259ff, 451

Gap in a Shell sort, 309

Interactive programming, 66 Interpreter, 24

Gates, Bill, 25, 458 General procedures (VB), 472, 475 GET statement, 400, 528 GotFocus event, 512, 607

GOTO statement, 38, 121, 256 Graphics, 408ff

Hercules card, 408 high-resolution, 409 with Visual Basic, 493ff GRAPHICS.COM, 409 Graphing functions, 418ff solutions to differential equations, 422 vertical asymptotes, 420 Greatest integer, 82

Iteration, 185, 256

Jacket, diskette, 16

Jacopini, Guiseppe, 24 Jobs, Stephen, 25 John Hancock building, 137 Kapor, Mitchell D., 26

Kemeny, John G., 24 Key Alt, 8, 11, 13 Backspace, 6, 13, 558

Caps Lock, 7 Hard copy of a program, obtaining, 1 S6R 513 Hard copy of output, 97-98 Hardware, 4 Height of projectile, 84 Help, 564, 565, 569, 587-588 Help screen, 11 Hercules graphics card, 408 Hierarchy chart, 33

High-resolution graphics, 409

INSTR, 57, 529 INT, 82, 529 key, 6 LBOUND, 294, 530 LEFT$, 56, 399, 530 LEN N17 995590 LOC, 401, 531 LOG, 79, 534 managing, 571-572 MID$, 56, 532 numeric, 78 Poisson probability, 253 RIGHTS, 56, 539 RND, 82, 428ff, 454, 539

Hoff, Ted, 25 Hollerith, Herman, 22

SGN, 82, 541 SIN, 80, 541 SOR, 79, 542 STR$, 542 string-valued, 56 TAB, 93, 98, 543 TAN, 80, 543 trigonometric, 80 UBOUND, 294, 544 UCASE$, 56, 544 user-defined, 83, 242 VAL, 544 zero of a, 173, 206 Fylstra, Dan, 25

Invoking QBasic, 566 Invoking Visual Basic, 461, 584 IS keyword in CASE, 133, 138

coordinate systems, 548

illegal call error, 85

RTRIM$, 392, 540

Inverse tangent, 80

Home key, 7, 13, 558 Hopper, Grace M., 23 Hotkey, 580 IF statement, 117, 529 block, 117, 147 block, confusing, 121 ELSEIF clause, 120

Illegal function call, 85 Immediate window, 5, 6, 550

using, 574 Increment, 186, 187 Index hole of a diskette, 15

Inequality, 112, 138 Infinite loop, 158 Initial value, 185 Input, 3, 28 INPUT statement, 66, 529

Inputting from a file, 359 Ins key, 7, 13, 559 Insert mode, 7 Installing Visual Basic, 461, 584 INSTR function, 57, 529 INT function, 82, 529 INTEGER identifier in DIM, 396 Integer,84, 85, 396 division, 85 long, 85

Cirle Ctrl+End, 11 Ctrl+Home, 11 Cursor Down,

13

Del, 7, 13558 End, 7, 13, 558 Enter, 8, 13 Esey 50, 19

Jel, Wl, Sxei7/ F2, 214 F4, 10 P55 ll; SS F6, 550 F7, 552, 596 lett, ‘oy? F9, 552 F10, 552 function, 6 Home, 7, 13, 558 Insy 7) 164559

Num Lock, 6, 13 PgDn, 558 PgUp, 558 PrtSc, 409 sequence,

11

Shift, 7, 13 Shift+F1, 6, 11, 569 Shift+F2, 214 Shift+F5, 10, 11, 567 Tab, 7, 467 toggle, 6 Key field of an array, 317 Keyboard, 2, 6 Keypad, numeric, 6 Keyword, 9, 45 KeyPress event, 512, 608 KILL statement, 20, 530 Knuth, Donald E., 25 Kurtz, Thomas E., 24

669

Index

670

Label, 15, 121, 549 Label (VB), 462, 466, 511 Last point referenced,413, 547-548 LBOUND function, 294, 530 Leading space, 44

Managing (VB) menus, 588-589 procedures, 593-594

Least squares approximation,

Mathematical notation, 40 Matrix, 327

203-204 LEFT$ function, 56, 530 LEN function, 57, 399, 530

Length field, 392

of file, 401 LET statement, 42, 53, 530 Library, 233

Line method, 493, 512, 609 LINE statement, 411, 413, 426, 530-531 Line choosing starting point when debugging, 553 clipping, 413 drawing a, 411 entering a, 12

feed, 44 number, 121 Loading a program, 560-561, 567

programs, 585 windows, 594-595

and vector multiplication, 328 Mauchley, John, 23 Mazer, Stan, 25 Memory, 2, 548 Menu bar, 5, 6, 11 Menus, 569-570, 588-589 Windows 580-581

Menu-driven program, 155 Merge algorithm, 290 Merging files, 370 Metacommand, 549

Methods, 477 Microprocessor, 2 Midpoint rule, 199, 259 MID$ function, 56, 532 Mills, Harlan B., 25

LOG function, 79, 531

MOD operator, 85 Mode graphics, 409 insert and overwrite, 7 text, 408 Modular design, 214, 254-256 Module, 33, 254 Modulo, 85

Logarithm

Monitor, 2

arbitrary base, 86 common, 86 natural, 79 Logical operator,112, 113, 147 LONG identifier in DIM, 396

Monte Carlo method, 446 Mouse, 575

LOC function, 401, 531 Local variable, 232, 267 LOCATE statement, 94, 531

LOF function, 401, 531

Long integer, 84, 85, 396 integer variable, 396 Lookup, table, 315 Loop, 152 DO, 152, 200, 524 FOR...NEXT, 189, 201, 527 infinite, 158 nested, 170, 190 structure, 36 LostFocus event, 473, 512, 609 LPRINT statement, 98, 532

Machine language, 3 Main body, 209 Managing (QB) debugger, 573-574 dialog box, 569-570 editor, 567-568 menus, 570 procedures, 571-572

programs, 566-567 windows, 572-573

scientific, 41 NotePad, 492 Noyce, Robert, 25 Null string, 58 Num Lock key, 6, 13, Numeric constant, 40, 104 expression, 43 function, 78 keypad, 6 variable, 42 variable types, 84 Objects (VB), 461ff, 511 OPEN statement, 356, 534 Opening a file for append, 358 for input, 359 for output, 357 Open, environment command, 560 Operator arithmetic, 40, 105 integer division, 85 logical, 112, 113, 147 MOD, 85 relational, 112, 147 OR logical operator, 113 Order, ascending and descending, 287 Ordered array, 287 search of, 288 Out of data error, 69 Output, 3, 28 Output screen, 10 Overwrite mode, 7

clicking, 576 double-clicking, 576

Parallel array, 278

dragging, 576 pointing, 575 using a, 517ff

Parameter, 211, 212, 242 Parent directory, 583 Parenthesis, 45 Pascal, 158

Moving text, 558-559, 568, 586 MsgBox, 488, 512, 611

MultiLine property, 464, 468, 611 Multiplication, 40

Name property, 467, 477, 612 NAME

statement, 20, 532

Naming a program, 567, 585 Natural logarithm, 79 Nested loop, 170, 190

Nesting, 121 NewPage method, 488, 612 New program, starting, 10 Newton-Raphson Algorithm, 206 New, environment command, 560 NEXT statement, 186 NEXT without FOR error, 190

NOT logical operator, 113, 532-533 Notation

mathematical, 40 QBasic, 40

Pass, 306 Passing, 209

arrays, 291 by reference, 228 records, 395 values, 227 variables, 227, 242 Path, 17 Pause, 70 Personal computer, 2 PgDn key, 558 PgUp key, 558 Pi, 80 Picture box, 462, 466-467, 512 Picture property, 466, 512, 612 Point, last referenced, 413, 547-548 Precision, double and single, 84, 85 Print method, 472, 512, 613 PRINT statement, 40, 44, 92, 536-537

Index

PRINT USING statement, 94, 99, 537 Print zone, 92, 98

Printed output, obtaining, 97-98 Printer, 2

Radian measure, 546 Random number, 82, 428 Random walk, 456 RANDOMIZE statement, 429, RANDOMIZE

PrintForm method, 489, 613 Printing a program, 561, 573, 595 Printing the screen, 97, 409 Problem solving, 4 Procedure, 208, 245

431, 454 Randomz-access file, 361, 399, 405, 548-549 Range array, 273, 276 determining for an array, 294 specifying in CASE, 133 subscript out of error, 278 Rational addition, 406

event, 472 general, 472, 475

managing, 571-572, 593-594 Procedure, function, 242 Procedure step, 551, 552, 596 Processing, 3, 28 control break, 371 Program, 3 choosing a starting line, 553

clearing from memory, 560, 567 development cycle, 29

TIMER statement,

READ statement, 63, 539

Reading from a file, 359 Read/write window, 16 Receipt, check-out, 377

Record, 392, 405

passing, 395 type, 392 variable, 393

menu-driven, 155 naming, 567, 585

ReDim, 489, 512, 613 Reference number of a file, 356, 382 Relational operator, 112, 147 Relative file, 401 REM statement, 67-68, 70, 539

printing, 561, 573, 595

Removing a breakpoint, 552, 596

running, 563, 566-567, 585 saving, 10, 561, 567 starting new, 10

Removing an array, 278 RENAME command (DOS), 20 Reserved word, 9, 45, 490 Restore button, 578 RESTORE statement, 65, 539 RIGHTS$, 56, 539 RND function, 82, 428, 454, 539 Root directory, 17, 583 Roulette, 436 Rounding, 82-83, 84 RTRIM$ function, 392, 540

item, 577

loading, 560-561, 567 Manager, 576-577

Programmer, 4 Programming development cycle, 29 interactive, 66

structured, 24, 25, 256

stub, 258 style, 70, 121, 158, 214, 278 Project, 460, 464 Project window, 462 Prompt, 66 Properties window, 462 how to access, 591-592 PrtSc key, 409 PSet method, 493, 512, 613 PSET statement, 412, 426, 538 Pseudocode, 31, 33, 38 Pseudo-random, 433 PUT statement, 399, 538 QBasic, 4 converting programs to Visual

Basic, 485ff exiting, 11, 561, 566 invoking, 566 notation, 40 QBColor, 493, 512, 613 Question mark, 66 Quotation mark, 59

Run, 9 Running a program, 563,

566-567, 585

Sampling, 432 Saving a program, 10, 561, 567 Scalar product, 303

Scale property, 493, 512, 614 ScaleMode property, 487 Scientific notation, 41 SCREEN statement, 409, 540 Screen

dump, 409 help, 11 output, 9, 10

printing, 97, 409 Scroll bar, 579 Search and replace, editor command,

562, 568

binary, 293, 313, 345

of ordered array, 288 sequential, 293, 313, 345

Searching, 313 Secant, 86

454, 538

Printer object, 488

displaying, 214, 562, 593

671

Seeding random number generator, 429 SELECT CASE statement, 132,

147, 541 Selector, 133, 147 Semicolon, 44 Sentinel, 167, 172, 200 Sequence structure, 34

Sequential file, 356 file sorting, 368 search, 293, 313, 345 SetFocus method, 477-478, 615

Setting a breakpoint, 552 Settings box, 463 SGN function, 82, 541 Shell sort, 24, 309, 345

gap, 309 Shell, Donald, 24 Shift key, 7, 13 Shift+F1 key, 6, 11, 569 Shift+F2 key, 214 Shift+F5 key, 10, 11, 567 Shockley, William, 24 Shortcut keys, 581 Shuffling of array elements, 431 Sign function, 82

Simple variable, 272 Simpson’s rule, 261 Simulation, 430 SIN function, 80, 541 SINGLE identifier in DIM, 390, 396

Single-precision, 84, 85, 396 variable, 390, 396

Single-subscripted variable, 323 Sizing handles, 462 Slope of a function, 175 Slot machine, 439 Smart editor, 12

Software, 4 Sort bubble, 305, 307, 345 DOS SORT command, 373 efficiency, 311 flagged bubble sort, 317 gap in Shell sort, 309 of a file, 368-369 of an array, 305 Shell, 24, 309, 345 Sorting, 305, 309

Space, leading and trailing, 44 Spaghetti code, 256 Specifying a coordinate system, 409 Spindle hole, 15 Spreadsheet, 25, 337ff

672

Index

SOR function, 79, 542 Square root, 79 Standard BASIC, 4 Standard deviation of data, 346 Starting line for debugging, 553 Statement, 9 Static array, 549 Status bar, 5, 6 STEP keyword in FOR, 187, 201 Step, ordinary and procedure, 552 Step value, 187 Stepping while debugging 551, 596 Stepwise refinement, 254 Stop execution at cursor, 552 STR$, 58, 542 STRING identifier in DIM, 390 String constant, 53, 104 empty, 58

expression, 54 fixed-length, 390-391, 405 format, 94 null, 58

string-valued function, 56 substring, 56 variable, 53 variable-length, 53 String-valued function, 56 Structure decision, 34

loop, 36 sequence, 34 Structured programming, 24, 25, 256 Stub programming, 258 SUB statement, 208, 543 Subdirectory, 17, 575

Subprogram, 208 managing, 571-572 Subroutine, 549 Subscript, 272

TAN function, 80, 543 Tangent, 80 Terminating value, 187

Text block, 559 copying, 561, 586 mode, 408 moving, 558-559, 568, 586 property, 463, 511, 616

numeric types, 84 passing, 227, 242

THEN keyword in IK 117 Title bar, 5,578 TO

string, 53

in CASE statement, 133 in FOR loop, 185

Toggle key, 6 Toolbox, 462 Top-down chart, 31, 33

design, 214, 234, 254-256 Trailer value, 167, 200 Trailing space, 44 Trapezoidal rule, 260

single-precision, 390, 396

single-subscripted, 323 subscripted, 272 Vector, 327 Vertical asymptote, graphing, 420 View window, 5 altering appearance of, 572-573 Visual Basic, 458-513 controls, 461 ff events, 47 Lff exiting, 584

HOW TOs, 584-596 installing, 461, 584 introduction to, 458-461 invoking, 461, 584

Truncate, 82

Primer edition of, 461

Truth value, 114 Turing, Alan, 23 Two-dimensional array, 323, 345 TYPE statement, 393, 543-544

printing programs, 595 properties, 462ff Standard edition of, 461

Type-declaration tag, 84 UBOUND

Statements, etc., 597-619 versions, 460-461 Von Neumann, John, 23

function, 294, 544

UCASE$ function, 56, 544 Ulam, Stanislaw, 23 Universal product code, 377 UNTIL keyword in DO loop, 152 WRC BT User, 4, 66 User-defined function, 83, 242 Using the editor, 561, 567-568,

Subtraction, 40 SWAP statement, 305, 317, 543 Sydnes, William L., 26 Syntax error, 10, 45, 69

VAL, 57, 544 Value ASCII, 55, 515-516, 569 default, 46, 546 initial, 185

list 132

Tab key, 7, 467 Table ASC, 55,515-516,569 display of ASCII, 59 editing commands, 558 frequency, 277 lookup, 315 Tag type-declaration, 84 Onis! %, &, !, and #, 84

simple, 272

objects, 461ff

586-587 Using the Immediate window, 574

TAB function, 93, 98, 543

record, 393

Trapping of events, 549 Trigonometric function, 80

Subscript out of range error, 278 Subscripted variable, 272 Substring, 56

System unit, 2

local, 232, 267 long integer, 396 numeric, 42

WHILE keyword in DO loop, 152 Wild card characters, 20, 560 Wilkes, Maurice V., 24 Window,

dialog, 9, 21, 569-570 Immediate, 5, 6, 550 Immediate, using, 574 managing, 572-573, 594-595 read/write, 15, 16 View, 5

View, altering appearance of, 5712-573 WINDOW statement, 410-411, 426, 546 Windows ending, 583

array, 272

how to utilize environment, 589-590 introduction to, 575-583 starting, 576-577 starting programs in, 578, 581 Wozniak, Stephen, 25 WRITE statement, 357, 546 WRITE# statement, 357, 546

control, 186, 201, 372 counter, 288

Write-protect notch, 15 Writing to a file, 357

passing, 227 step, 187 terminating, 187 trailer, 167, 200 truth, 114 Variable, 42, 104, 272

double-precision, 84, 396 double-subscripted, 323 integer, 84, 396

Zero of a function, 173, 206

Index of Selected Engineering, Mathematics, and Science Applications Chapter 3

Water use in the United States (Exercise 69, p. 51) Weight in grams of a mole (Exercise 70, p. 52) Distance of Sirius from Earth (Exercise 72, p. 52)

Time required for a baseball to reach home plate (Exercise 74, p. 52) Volume of the Earth (Exercise 46, p. 61) Pressure of a liquid (Exercise 6, p. 71)

Potential and kinetic energy (Exercise 8, p. 72) Stress produced on a bar by a force (Exercise 18, p. 73) Distance of a storm (Exercise 25, p. 75)

Ductility of a material in tension (Exercise 26, p.74) Calories burned during exercise (Exercise 27, p. 75) Training heart rate (Exercise 28, p. 75) Acceleration of gravity as a function of elevation (Exercise 30, p. 76) Atom density of isotopes (Exercise 34, p. 77)

Pythagorean theorem (Example 2, p. 79-80) Ballistic trajectory (Example 4, p. 81) Conversion of degrees to radians (Example 5, p. 82) Surveying (Example 5, p. 82) Distance of a point from the origin (Example 9, p. 84) Hyperbolic functions (Exercise 32, p. 88)

Stopping distance for a car (Exercise 39, p. 89) Velocity of a neutron (Exercise 40, p. 89) Moment of a force (Exercise 42, p. 89) Radioactive decay (Exercise 43, p. 89) Age of a rock (Exercise 44, p. 89) Law of cosines (Exercise 45, p. 90) Impedance of a circuit (Exercise 46, p. 90) Period of a pendulum (Exercise 47, p. 90) Harmonic mean of two numbers (Exercise 48, p. 90)

Conversion of polar to rectangular coordinates (Exercise 49, p. 90) Trajectory of a shot put (Exercise 50, p. 90) Taylor polynomial approximation of the sine function (Exercise 51, p. 90) Distance between two points (Exercise 52, p. 90) Radius of a circle in terms of its area (Exercise 53, p. 90) Rounding of a number to n decimal places (Exercise 57, p. 91) Conversion of nautical to standard hours (Exercise 59, p. 91) Base units of the metric system (Exercise 34, p. 102-103)

Conversion of U.S. to metric system lengths (Programming Project 6, p. 107) Number of calories in a food (Programming Project 7, p. 107) Construction of a trigonometric table (Programming Project 10, p. 108) Resistance of a conductor (Programming Project 11, p. 108) General law of perfect gases (Programming Project 12, p. 109) Kepler’s Third Law (Programming Project 13, p. 109) Chapter 4

Equivalent resistance for a circuit (Exercise 10, p. 124) Behavior of perfect gases (Exercise 12, p. 124-125)

Volumes of geometric objects (Exercise 16, p. 126) Force on a particle (Exercise 38, p. 129)

Mass number of chemical elements (Exercise 40, p. 129) Work done in changing the elongation of a spring and bar (Exercise 46, p. 130) Determination of the number of digits in a number (Exercise 49, p. 131)

673

674

Index

Addition and display of complex numbers (Example 5, p. 135-137) Rotation of a body with constant angular acceleration (Exercise 10, p. 141) Cloudiness descriptors (Exercise 33, p. 144) Areas of geometric objects (Exercise 36, p. 145) Percent of calories from fats (Programming Project 1, p. 147) Real roots of a quadratic equation (Programming Project 2, p. 147) Impedance of a circuit (Programming Project 4, p. 148-149) The nth root of a complex number (Programming Project 5, p. 149) Solution of a pair of linear equations (Programming Project 7, p. 149) Genetics (Programming Project 8, p. 149-150) Chapter 5

Decibel level of a sound (Example 2, p. 153)

Length, midpoint, and slope of the line joining two points (Example 5, p. 156-157) Resultant of forces acting on a body along the same axis (Exercise 4, p. 160) Atmospheric pressure (Exercise 11, p. 162) Molality of a solution (Exercise 12, p. 162)

Number of revolutions per minute of a generator (Exercise 24, p. 163) Conversion of Celsius to Fahrenheit (Exercise 25, p. 163)

Newton’s 2nd law and the equation of motion (Exercise 26, p. 163) Grains of wheat on a chess board (Exercise 32, p. 164) Solution of a linear equation (Exercise 35, p. 164) Coefficient of restitution of a ball (Exercise 37, p. 165) Current-voltage relationship in an ideal diode (Exercise 40, p. 165)

Change in the dimensions of a block due to a change in temperature (Exercise 42, p. 165) Prime factors of a number (Exercise 44, p. 166) Greatest common divisor (Exercise 45, p. 166)

Speed of a boat after the motor is turned off (Exercise 46, p. 167) Bisection method for finding a zero of a function (Example 7, p. 174-175) Derivative of a function (Example 8, p. 176) Surface tension of certain liquids (Exercise 10, p. 179) SI units and their symbols (Exercise 16, p. 180)

Equivalent capacitance in a parallel circuit (Exercise 20, p. 181) Physician’s abbreviations (Exercise 21, p. 181-182) Recursive algorithm (Exercise 23, p. 182)

Kingdoms of living things (Exercise 24, p. 182-183) Bisection method for finding all zeros of a function (Exercise 32, p. 184)

Determination of a zero of a polynomial (Exercise 33, p. 184) Average acceleration (Exercise 21, p. 193)

Sum of the reciprocals of integers (Exercise 29, p. 194) Sum of an arithmetic sequence (Exercise 30, p. 194) Mean value of a resistance (Exercise 32, p. 194) Voltage and current in an R-C series circuit (Exercise 34, p. 195) Ideal weights for men and women (Exercise 35, p. 195) Magnetic field produced by an electric current (Exercise 38, p. 196) Radioactive decay (Exercise 43, p. 196) Recursive generation of a sequence of numbers (Exercise 48, p. 197-198)

Proper divisors of an integer (Exercise 52, p. 198) Deflection of a beam (Exercise 53, p. 198-199)

Midpoint rule for approximating a definite integral (Exercise 54, p. 199) Snell’s Law (Exercise 56, p. 200) Half-life of radioactive elements (Programming Project 2, p. 201)

Least squares line (Programming Project 6, p. 203-204) Height of a ball thrown in the air (Programming Project 7, p. 205) Modeling of air pollution in a city (Programming Project 9, p. 206) Newton-Raphson algorithm for finding a zero of a function (Programming Project 10, p. 206)

Chapter6

Angular frequency (Exercise 16, p. 219) Force needed to stretch a spring (Exercise 20, p. 220)

675

Molarity of a solution (Exercise 21, p. 220)

Pressure produced by a force acting on specific area (Exercise 56, p. 225) The n nth roots of a complex number (Exercise 62, p. 226)

Flash point of a liquid (Exercise 6, p. 235) Change in the length of an axially loaded bar under compression (Exercise 10, p. 236) Temperature rise from the compression of a perfect gas (Exercise 20, p. 238) Conversion of feet and inches to centimeters (Exercise 31, p. 240) Different forms for the equation of a line (Exercise 41, p. 241) Number of positive, negative, and zero values of a function (Exercise 42, p. 241)

Power of a complex number (Exercise 43, p. 241) Hypotenuse of a right triangle (Example 2, p. 243) Binomial coefficients (Example 3, p. 243-244) Flexibility of an axially loaded steel bar (Exercise 2, p. 246-247) Number of atoms in a substance (Exercise 4, p. 247) Oil consumption (Exercise 10, p. 248-249) Number of moles of atoms in a substance (Exercise 16, p. 250) Coulomb’s law (Exercise 18, p. 250) Training heart rate (Exercise 22, p. 251) Factorial of a number (Exercise 28, p. 252)

Accuracy of Stirling’s formula (Exercise 29, p. 252) Number of real roots of a quadratic equation (Exercise 30, p. 252) Number of prime factors of a number (Exercise 31, p. 252) Least common multiple of two numbers (Exercise 32, p. 252) Heron’s formula (Exercise 34, p. 252) FORTRAN’s ATAN2(y,x) function (Exercise 35, p. 252)

Amount of water displaced by a sphere (Exercise 36, p. 252-253) Conversion of feet to meters Prime numbers (Exercise 38, Arccosine function (Exercise Poisson probability function

and vice versa (Exercise 37, p. 253) p. 253) 39, p. 253) (Exercise 42, p. 253)

Binary representation of a positive integer (Exercise 43, p. 253) Average value of a function (Exercise 44, p. 254)

Numerical integration (Case Study, p. 259-267) Velocity and acceleration of the moon (Programming Project 1, p. 267-268) Mass composition of a substance (Programming Project 2, p. 268) Heat necessary to increase the temperature of a metal (Programming Project 3, p. 268) Conversion between deg-min-sec, decimal degrees, and radians (Prog. Pr. 4, p. 268)

Analysis of a quadratic function (Programming Project 5, p. 268-269) Number palindromes (Programming Project 6, p. 269) Perfect numbers (Programming Project 7, p. 269)

Symbolic addition (Programming Project 8, p. 269) Taylor polynomial approximation (Programming Project 9, p. 270) Chapter 7

Effect of an increase in temperature on the length of a bar (Exercise 4, p. 279-280) Power received at the Earth’s surface (Exercise 6, p. 280) Morse code (Exercise 32, p. 284-285) Velocity flow of a fluid (Exercise 34, p. 285) Tensile strength test of steel (Exercise 36, p. 285-286)

Histogram of missile velocities (Exercise 37, p. 286) Current at a branch point (Exercise 32, p. 301) Speed of sound in various substances (Exercise 36, p. 301) Moh’s hardness scale for minerals (Exercise 38, p. 302) Inner product of two vectors (Exercise 43, p. 303)

Center of mass of a system of particles (Exercise 44, p. 303) Boiling points of substances (Exercise 45, p. 303) Atomic data for some elements (Exercise 48, p. 304) Planet data (Exercise 26, p. 320)

Chemical elements found in animals (Exercise 32, p. 322)

676

Index

Boiling points of metals (Exercise 34, p. 322) Nutritional components of foods (Example 2, p. 325-327)

Multiplication of a vector by a matrix (Example 3, p. 328-329) Heat capacity of a material (Exercise 2, p. 329) Magnetic energy stored in an inductor (Exercise 8, p. 330) Period of a pendulum (Exercise 16, p. 331) Matrix multiplication (Exercise 18, p. 332) The nth power of a matrix (Exercise 20, p. 332) Matrix addition (Exercise 21, p. 332)

Transpose of a matrix (Exercise 22, p. 332) Chemical composition of substances (Exercise 25, p. 332-333)

Widths of two-lane highways (Exercise 27, p. 333) Magic squares (Exercise 34, p. 335-336) Monthly precipitation (Exercise 35, p. 336)

Perimeter of a polygon (Exercise 36, p. 336) Euclidian norm of a matrix (Exercise 37, p. 336)

Calculating with a spreadsheet (p. 337-345) Conversion of lengths to various units (Programming Project 1, p. 346) Mean and standard deviation used to curve grades (Programming Project 2, p. 346) Language translation (Programming Project 3, p. 347) Evaluation, differentiation, and integration of polynomials (Prog. Pr. 7, p. 348-349) Elementary row operations on matrices (Programming Project 8, p. 349) Matrix inversion (Programming Project 9, p. 350) Intersection and union of sets (Programming Project 10, p. 350) Solving an electric circuit (Programming Project 11, p. 350-351) Game of Life (Programming Project 12, p. 351) Linear shift registers (Programming Project 13, p. 352-353 Chapter 8

Thermal conductivity (Exercises 23, 25, 26, p. 366-367) Flow of heat through a material (Exercise 24-26, p. 367) Quality control (Exercise 30, p. 367) Radioactive elements (Exercises 5-7, p. 374) Densities of metals (Exercise 10, p. 375) Burn rates of rocket propellants (Exercise 12, p. 375) Prime factorization of a number (Programming Project 5, p. 384)

Frequencies for the visible spectrum (Programming Project 6, p. 384-385) Astronomical data (Programming Project 7, 8, p. 385-386) Fuel economy (Programming Project 9, p. 387)

Chapter9

Chapter 10

— Rational addition (Programming Project 3, p. 406)

Graphs of straight lines (Exercises 27 & 28, p. 417) Graphs of functions (Examples 1 & 2, p. 418-421) Euler’s method for solving differential equations (Example 3, p. 422-423) Taylor polynomial approximations of e* (Exercises 19 & 20, p. 424) Tangent line to a graph (Exercise 24, p. 425) Secant line approximation of the tangent line (Exercise 25, p. 425) Inverse of a function (Exercise 27, p. 425)

Polar coordinate graphs (Programming Project 1, p. 426) The derivative of a function (Programming Project 3, p. 426) Chapter 11

Simulation of a line at the box office (Exercise 24, p. 434) Selection of a subset of a set (Exercise 27, p. 434-435)

Birthday problem (Exercise 29, p. 435) Simulation of tellers serving bank lines (Examples 1 & 2, p. 446-449) Monte Carlo estimation of the area under a curve (Example 4, p. 451-452) Simulation of airline overbooking of a flight (Exercise 8, p. 453) Game Theory (Programming Project 2, p. 455) Random walk (Programming Project 3, p. 456) Knight’s tour (Programming Project 4, p. 456)

The diskette in this book has two subdirectoriee—EXAMPLES and VBPRIMER.

Examples The subdirectory EXAMPLES contains all the programs from the examples and case studies of this textbook. The QBASIC case study programs have the suggestive names INTEGRAL.BAS, SPRSHEET.BAS, and CHECKOUT.BAS. The other QBasic programs have names of the form chapter-section-number.BAS. For instance, the program in Chapter 3, Section 2, Example 4 has the name 3-2-4.BAS. Visual Basic examples have

the same type base name, but end in .MAK. The following steps open these programs. (Assume that the diskette is in the A drive.) 1. Press Alt/F/O

2. Enter

A:\EXAMPLES

3. Press Tab

4. Cursor to the desired program (Note: To move quickly to the beginning of the programs from Chapter 3, press 3.) 5. Press the Enter key.

VBPRIMER The files in this subdirectory are used to install the Primer Edition of Visual Basic 2.0 on the hard disk of a computer on which Windows has been installed. To install Visual Basic follow the steps in part A on page 584. Note: If your computer does not have a standard configuration, you might be asked one or two additional questions during the installation process.

MICROSOFT SOFTWARE LICENSE READ THIS FIRST. Your use of the Microsoft software (the “SOFT WARE”)

is governed by the legal agreement below.

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THE SOFT WARE AND ACCOMPANYING WRITTEN MATERIALS (INCLUDING INSTRUCTIONS FOR USE) ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND. FURTHER, MICROSOFT DOES NOT WARRANT, GUARANTEE, OR MAKE ANY REPRESENTATIONS REGARDING THE USE, OR THE RESULTS OF THE USE, OF THE SOFTWARE OR WRITTEN MATERIALS IN TERMS OF CORRECTNESS, ACCURACY, RELIABILITY, CURRENTNESS, OR OTHERW&3E. THE ENTIRE RISK AS TO THE RESULTS AND PERFORMANCE OF THE SOFTWARE IS ASSUMED BY YOU. IF THE SOFTWARE OR WRITTEN MATERIALS ARE DEFECTIVE YOU, AND NOT MICROSOFT OR ITS DEALERS, DISTRIBUTORS, AGENTS, OR EMPLOYEES, ASSUME THE ENTIRE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. The diskette in this book was reproduced by Dellen Publishing Company under a special arrangement with Microsoft Corporation. For this reason, Dellen Publishing Company is responsible for the product warranty and for support. If your diskette is defective, please return it to Dellen Publishing Company, which will arrange for its replacement. In no event shall Microsoft’s liability and your exclusive remedy as to defective software, written materials, and disks be other than either (a) return of the purchase price or (b) replacement of the disk which is returned to

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KE MEMORIAL LIBRARY ea C. SMITH UNIVERSITY CHARLOTTE, N. C. 28216

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1994 I.