Table Of ContentBARRON’S
COMPUTER PROGRAMMING
WAY
READ,A, B,C
SUM
Your Key to Learning
by Lawrence S. Left and Arlene Podos
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COMPUTER PROGRAMMING
FORTRAN
THE
EASY
WAY
BY
Lawrence S. Leff
Assistant Principal and
Chairman, Department of Mathematics
Franklin D. Roosevelt High School
Brooklyn, New York
AND
Arlene Podos
Lecturer in Data Processing
Queensborough Community College
Bayside, New York
Barron's Educational Series, Inc.
New York/London/Toronto/Sydney
© Copyright 1985 by Barron's Educational Series, Inc.
All rights reserved.
No part of this book may be reproduced
in any form, by photostat, microfilm, xerography,
or any other means, or incorporated into any
information retrieval system, electronic or
mechanical, without the written permission
of the copyright owner.
All inquiries should be addressed to:
Barron’s Educational Series, Inc.
250 Wireless Boulevard
Hauppauge, New York 11788
Library of Congress Catalog Card No. 84-18526
International Standard Book No. 0-8120-2800-7
Library of Congress Cataloging in Publication Data
Leff, Lawrence S.
Computer programming in Fortran the easy way.
Includes index.
1. FORTRAN (Computer program language) I. Podos,
Arlene. II. Title.
QA76.73.F25L435 1984 001.64'24 84-18526
ISBN 0-8120-2800-7
PRINTED IN THE UNITED STATES OF AMERICA
890 100 98765432
Dedication
To my husband, Don, my sons, Steve and Jeff, my mother, Shirley Drimmer, and my best friend,
Beverly Rosendorf.
Arlene Podos
Acknowledgments
We would like to thank the staff of the University Computer Center of the City University of
New York for providing us with the technical and hardware support which allowed us to illustrate
Fortran concepts using the popular WATFIV compiler.
Rex Franciotti, Director of Computer and Communications at Adelphi University, and Charles
Wilcox, Academic Systems Analyst at Adelphi University, made it possible for us to present the
major features of Fortran 77 using a PRIME 850 computer.
Melchiore LaSala of Queensborough Community College provided encouragement and sup¬
port. Ms. Beverly Rosendorf helped to shape the manuscript by making many valuable sugges¬
tions.
A Special Word of Thanks to . . .
Our editor, Joan Cipriano. Joan's confidence and energies helped to make this book a reality.
Contents
PREFACE
INTRODUCTION
CHAPTER 1 COMPUTER FUNDAMENTALS
1.1 What Is A Computer Program? 1
1.2 What Can A Computer Do? 2
1.3 The Nature of a Computer 5
1.4 Input and Output Devices 7
1.5 Computer Software 10
1.6 Internal Data Representation and Memory 11
1.7 The Hierarchy of Computer Languages 12
1.8 Representing Numbers and Data Precision 14
1.9 The Field-Record-File Concept 16
1.10 Types of Program Language Statements and Flowcharts
1.11 Structured Programming 22
1.12 Reading and Interpreting Flowcharts 24
1.13 Pseudocodes 30
1.14 Some Closing Remarks 30
Review Exercises 32
CHAPTER 2 ELEMENTS OF FORTRAN
2.1 Computer Memory and Fortran Variables 34
2.2 The Assignment Statement 37
2.3 Some General Features of a Fortran Program 39
2.4 List-Directed (Format-Free) Input and Output 43
2.5 Data Declaration Statements 45
2.6 Syntax versus Logic Errors 49
2.7 Some Closing Remarks 50
Review Exercises 53
CHAPTER 3 MORE ON INPUT, OUTPUT, AND
PROCESSING 55
3.1 Evaluating Fortran Expressions 55
3.2 Writing Fortran Expressions 58
3.3 Mixed-Mode Arithmetic 62
3.4 Explaining Computer Output 64
3.5 The GOTO Statement 65
3.6 Some Additional Details on Coding Fortran Statements 69
3.7 Column Headings 73
3.8 Planning a Fortran Program 74
3.9 Some Closing Remarks 78
Review Exercises 80
CHAPTER 4 CONTROLLING INPUT AND OUTPUT 83
4.1 Format-directed Input/Output 83
4.2 Controlling Vertical line Spacing 93
4.3 Some Additional Edit Descriptors 95
4.4 Testing for the End of a Data List 100
4.5 Counting and Accumulating Totals 102
4.6 Some Closing Remarks 105
Review Exercises 106
CHAPTER 5 DECISION STRUCTURES
5.1 Making Decisions: the Block IF 111
5.2 Single-Choice Decision Structures 117
5.3 The Logical and Arithmetic IF Statements 121
5.4 Using Decision Structures to Control Loops 123
5.5 Nested Decision Structures 130
5.6 Multiple-Alternative Decision Structures 135
5.7 The CASE and Computed GOTO Structures 139
5.8 The Logical .AND. and .OR. 143
5.9 Validating Input Data 145
5.10 Some Built-in Fortran Functions 146
5.11 Some Closing Remarks 151
Review Exercises 153
CHAPTER 6 DO LOOPS
157
6.1 The Anatomy of a DO Loop 157
6.2 Using the DO Loop in Fortran Programs 160
6.3 The Prime Number Problem 170
6.4 DO Loops Within DO Loops 174
6.5 Some Closing Remarks 179
Review Exercises 182
CHAPTER 7 SUBSCRIPTED VARIABLES
186
7.1 Storing a Data List as an Array 186
7.2 Manipulating the Elements of an Array 194
7.3 Sorting a List of Numbers 199
7.4 Searching an Array for a Particular Element 204
7.5 The Implied DO Loop 206
7.6 Multidimensional Arrays 211
7.7 The DATA and PARAMETER Statements 217
7.8 Some Closing Remarks 219
Review Exercises 220
CHAPTER 8
CHARACTER AND LOGICAL DATA
225
8.1 Character Data 225
8.2 Comparing Character Strings 226
8.3 Logical Data 228
8.4 Using a Program Flag 232
8.5 Manipulating Character Strings 233
8.6 Additional Character Functions 237
8.7 Notes on Format-Directed Input/Output of Character and
Logical Data 240
8.8 Some Closing Remarks 241
Review Exercises 242
CHAPTER 9 FORTRAN SUBPROGRAMS AND PROGRAM
STRUCTURE
244
9.1 Some Additional Fortran Library Functions 244
9.2 Programmer-Defined Functions 247
9.3 Creating Subroutine Subprograms 257
9.4 COMMON and EQUIVALENCE Statements 262
9.5 Problem Solving Approaches 269
9.6 Some Closing Remarks 273
Review Exercises 274
CHAPTER 10 EXTERNAL FILE PROCESSING
277
10.1 Organizing Data on Magnetic Media 277
10.2 File-Related Commands (Fortran 77) 277
10.3 Some Data Processing Applications 282
10.4 Some Closing Remarks 285
Review Exercises 286
Appendix: A Comparison of the Major Fortran Versions 289
Answers to Selcted Problems 292
Index 322
Introduction
Fortran (Formula Translation) was first introduced by IBM in the late 1950s. With the availabil¬
ity of “newer" programming languages such as PL/1 and Pascal, why study Fortran? The main
reason is that no other high-level language is as powerful and versatile in handling computation¬
ally based problems, yet as easy to learn. From a computer's standpoint, Fortran is an efficient
language. A Fortran compiler (the program that translates your Fortran program into the com¬
puter's own native machine language) is small compared to some other compilers, such as those for
Cobol and PL/1; additionally, Fortran programs execute rapidly. Fortran offers a wide variety of
built-in mathematical functions that may be referenced in a program. The availability of special¬
ized mathematical and statistical Fortran library programs that can be "plugged" into the programs
you write is another compelling advantage of the language.
As a result of Fortran's long history, and of some weaknesses in the original version, Fortran
has experienced a number of significant revisions. In 1966 the American National Standards
Institute (ANSI) issued a standardized version of Fortran that came to be known as Fortran IV.
Recognizing certain limitations of the ANSI Fortran standard, the University of Waterloo in
Ontario developed a student-oriented version of Fortran called WATFOR (Waterloo Fortran).
WATFIV, an enhanced version of WATFOR, remains a very popular Fortran dialect that is used in
many college-level Fortran programming courses.
The most recent standardized version of Fortran was defined by ANSI in 1977 and is referred to
as Fortran 77. The Fortran 77 standard clarified some ambiguities contained in the 1966 imple¬
mentation while adopting many of the language extensions introduced by WATFOR and WAT¬
FIV. Programs written in Fortran IV will generally run with little or no modification on systems
based on Fortran 77. The converse is not necessarily true, however; not all programs that run
successfully on Fortran 77 systems will execute on computers that use the earlier standard. Fortran
77 is better suited than Fortran IV for use in an interactive (terminal-oriented) environment. The
Fortran versions available with some desktop computers tend to be a subset of the Fortran 77
standard.
The designers of Fortran 77 have introduced features to make the language more compatible
with accepted principles of sound program design and construction that have come to be known as
structured programming. Improved capabilities in manipulating nonnumeric data, as well as in
processing external files maintained on secondary storage media such as magnetic tape and disk,
also distinguish Fortran 77 from its earlier Fortran relatives.
Because of the additional features offered by Fortran 77 and the continued popularity of
WATFIV on college campuses, the presentation in this book gives ample consideration to each of
these Fortran implementations.
