Table Of ContentProgramming
in C
Ram Kumar
Late, Professor, University of Udaipur, Udaipur
Late, Professor, Motilal Nehru Regional Engineering
College, Allahabad
Rakesh Agrawal
IBM Almaden Research Center, San Jose, California
West Publishing Company
St. Paul New York Los Angeles San Francisco
Production credits
Copyediting: Martha Knutson
Composition: Professional Book Center
Text Design: Lois Stanfield
Cover Design: Elaine Saint-Marie
COPYRIGHT © 1992 By WEST PUBLISHING COMPANY
610 Opperman Drive
P.O. Box 64526
St. Paul, MN 55164-0526
All rights reserved
Printed in the United States of America
99 98 97 96 95 94 93 8765432
Library of Congress Cataloging-in-Publication Data
Kumar, Ram.
Programming in ANSI C / Ram Kumar, Rakesh Agrawal
p. cm.
Includes bibliographical references and index.
ISBN 0-314-89563-9 (soft)
1. C (Computer program language) I. Agrawal, Rakesh. n. Title.
QA76.73.C15K86 1992
005.26'2—dc20 91-26474
CIP
For Mrs. Urmila Agrawal
with love and gratitude
Notices
IBM is a registered trademark of International Business Machines Corp.
Microsoft is a registered trademark of Microsoft Corp.
MS-DOS is a registered trademark of Microsoft Corp.
PDP and VAX are registered trademarks of Digital Equipment Corp.
Turbo C is a registered trademark of Borland International Incorporated.
UNIX is a registered trademark of AT&T.
WordPerfect is a registered trademark of WordPerfect Corp.
WordStar is a registered trademark of MicroPro International Corp.
The programs presented in this book have been included for their instruc-
tional value. The authors do not offer any warranties or representations, nor do
they accept any liabilities.
vi
Biographies
RAM KUMAR
Dr. Ram Kumar was Professor and Head of the Department of Mathematics,
University of Udaipur, Udaipur, and Motilal Nehru Regional Engineering Col-
lege, Allahabad. He was a noted scholar and was engaged in research and
teaching for over 40 years. He wrote several books, including the highly popu-
lar Programming with FORTRAN 77.
He was a holder of both Ph.D. and D.Sc. degrees. On his D.Sc. thesis, he
was awarded the Bonarjee Research Prize by the University of Lucknow for the
best research production of 1963. He was a Fellow of the National Academy of
Sciences, India.
RAKESH AGRAWAL
Dr. Rakesh Agrawal is a Research Staff Member at the IBM Almaden Research
Center, San Jose, California. He was a member of Technical of Staff at the AT&T
Bell Laboratories, Murray Hill, New Jersey from September 1983 to December
1989. He holds M.S. and Ph.D. degrees in Computer Science from the Univer-
sity of Wisconsin, Madison. He has published extensively in technical journals
and conferences. He is a co-designer of 0++, a database programming lan-
guage based on C++. He is an Editor of the IEEE Data Engineering and the
Database Technology, and was a Program Chairman of the 2nd International Sym-
posium on Databases in Parallel and Distributed Systems. He is a Senior Member of
IEEE and a Member of ACM.
vii
PREFACE
in order for you to develop an intuitive understanding of them. They are then
rigorously discussed in the remainder of the chapter. Each chapter ends with a
set of exercises that allow you to review and test your understanding of the
new material. Examples and exercises have beenv selected from various dis-
ciplines and application domains, including business, engineering, science,
mathematics, and statistics. Illustrative programs have been run and tested
under both UNIX and DOS environments.
Organization
We begin with an overview of the computer organization in Chapter 1. The
principal components of computer hardware — memory, control unit, arithme-
tic-logic unit, and input/output devices — are described. We then discuss com-
puter software and programming languages, explaining the differences
between machine, assembly, and higher level languages. A brief history of the
evolution of C is also given. We then describe the programming process: prob-
lem definition, program design, program coding, program compilation and
execution, program testing and debugging, and program documentation.
Algorithm development, which is the heart of computer programming, is also
discussed in this chapter.
We start learning the specifics of C in Chapter 2. A useful starting point for
understanding computer programming is that all programs can be written
using just three logical structures: sequential, selective, repetitive, or a combi-
nation thereof. We first discuss the sequential structure, which consists of one
operation followed by another, and then introduce some C constructs sufficient
to write simple sequential programs. In particular, we examine the main func-
tion, the C character set, various data types, variables and constants, arithmetic
operators, assignment statements, input and output functions, type conver-
sions, and simple macros.
The selective structure, which consists of a test for a condition followed by
alternative paths that the program can follow, is discussed in Chapter 3. Selec-
tion among alternative processing is programmed with certain decision-mak-
ing constructs: conditional statement, nested conditional statement, multiway
conditional statement, and constant multiway conditional statement. Besides
introducing these constructs, we also examine the relational, logical, and condi-
tional expression operators necessary for understanding these constructs.
The repetitive structure, also known as the iterative or loop structure,
allows a set of program statements to be executed several times even though
they appear only once in the program. This topic is discussed in Chapter 4. The
constructs presented include while loop, do-while loop, for loop, and nested
loops. The facilities for loop interruption are also discussed.
A C program is usually developed by dividing it into logically coherent
functional components, each of which carries out a specific task. We discuss the
user-defined functions in Chapter 5. In particular, we look at how a function is
defined and called, function prototypes, block structure, external variables,
storage classes, separate compilation and data abstraction, and recursion.
Arrays, which enable a user to organize and process a set of ordered data
items, are the subject of Chapter 6. We discuss array type declaration, arrav ini-
Preface
C
has emerged as the most widely used programming language for software
development. It is a small, yet powerful language. It features modem
control flow and data types that allow the development of well-structured
programs. Its data types and control structures are directly supported by most
computers, resulting in the construction of efficient programs. It is
independent of any particular machine architecture or operating system, which
makes it easy to write portable programs. It is this combination of rich control
structures and data types, ability to get close to computer hardware, efficiency,
portability, and concisenessi that has contributed to the popularity of C.
Audience
This book teaches computer programming using C. It does not presume prior
knowledge of some other programming language, and teaches C from first
principles. At the same time, it is a complete description of C. Even knowledge-
able C programmers should find the examples and exercises interesting and
challenging. This book can be used either as a textbook for a course on pro-
gramming, as a source book for a training course on C, as a guide for self-teach-
ing C, or as a reference by software professionals.
Approach
The text is designed in such a way that it gradually introduces new concepts,
gives examples based on the concepts introduced so far, and then builds on
what you have already assimilated. There is a strong emphasis on examples. The
book is full of illustrative programs that exemplify how different language con-
structs can be put together to solve a given problem. Examples in each chapter
have been chosen so that they not only embody the various language con-
structs introduced in that chapter, but also use the ideas learned in previous
chapters. In this way, concepts are reinforced and covered at a deeper level in
each new context. In several instances, the same problem has been solved using
different language constructs to clarify differences between them. Concepts are
first introduced informally through one or more motivating example programs
ix
PREFACE xi
tialization, and how array elements are accessed. We also study arrays as func-
tion arguments.
We examine in Chapter 7 one of the most sophisticated features of C: point-
ers. After introducing the basics of pointers, such as pointer type declaration,
pointer assignment, pointer initialization, pointer arithmetic, pointer compari-
son, and pointer conversion, we discuss the relationship between functions
and pointers, arrays and pointers, strings and pointers, and multidimensional
arrays and pointers. We then look at pointer arrays, pointers to functions, and
dynamic memory management.
Structures allow a fixed number of data items, possibly of different types,
to be treated as a single object, whereas unions allow a number of different
types of grouped data items to be referred to using the same name. These top-
ics form the subject matter of Chapter 8. Besides introducing the techniques for
defining and using structures and unions, we discuss the scope rules for struc-
ture definitions, structures as function arguments, structures as function val-
ues, nested structures, arrays of structures, structures containing arrays, struc-
tures containing pointers, and self-referential structures.
Systems programs frequently require the capability to manipulate individ-
ual bits of a word. C provides four operators, called bitwise logical operators,
for masking operations on bits, and two operators, called the bitwise shift oper-
ators, for shifting bits in a word. In addition, C allows a word to be partitioned
into groups of bits, called bit-fields, and names to be assigned to them. We
study these features in Chapter 9.
C does not provide language constructs for input/output (I/O) operations.
However, ANSI C has defined a rich set of functions to provide a standard I/O
system for C programs. We discuss in Chapter 10 the functions available in the
standard I/O library and their use in writing applications involving file pro-
cessing that require large amount of data to be read, processed, and saved for
later use.
The C preprocessor, which can conceptually be thought of as a program
that processes the source text of a C program before it is compiled, is the subject
of Chapter 11. The three major functions of the C proeprocessor discussed are
macro replacement, conditional inclusion, and file inclusion. Macro replace-
ment is the replacement of one string by another, conditional inclusion is the
selective inclusion and exclusion of portions of source text on the basis of a
computed condition, and file inclusion is the insertion of the text of a file into
the current file. In addition, the line, error, pragma, and null directives, and the
predefined macro names are also described.
We discuss some additional C features in Chapter 12. In particular, we
describe the type definition facility, which allows synonyms to be defined for
existing data types; the type qualification facility, which permits greater control
over program optimization; the enumeration type, which provides the facility
to specify the possible values of a variable by meaningful symbolic names; the
facility to define functions that take variable number of arguments; the storage
class specifier register, which can speed up programs by specifying to the com-
piler the heavily used variables to be kept in machine registers; facilities for
alternative representation of characters; and the goto statement, which can be
used to branch around one or more statements.
xii PREFACE
The book contains six appendices. Appendix A describes functions
included in the standard library but not presented in the text earlier. Appendix
B summarizes C operators together with their precedence and associativity.
Appendix C explains the main differences between ANSI C and the version of
C as described in Kernighan and Ritchie's 1978 book "The C Programming
Language." Those of you who still have pre-ANSI C compilers will find this
appendix particulary useful. Appendix D reviews the decimal, binary, octal,
and hexadecimal number systems, discusses how numbers in any one of these
systems can be converted into numbers in the others, and describes how num-
bers and characters are represented inside the computer. Appendix E gives a
table of ASCII and EBCDIC character codes and equivalent representations of
some decimal numbers in the binary, octal, and hexadecimal systems. Appen-
dix F lists some classical references on programming and C.
We believe that the best way to learn programming is by reading, writing,
and experimenting with programs. To increase your understanding of C, we
encourage you to read and re-read the example programs given in the book
and to solve as many exercises as you can. We also encourage you to experi-
ment with the programs by running them with different test inputs, by modify-
ing them to use alternate constructs, and by enhancing them with error check-
ing and additional functionality. The source code for the programs given in the
illustrative examples has been made available on a compainion diskette to aid
this process.
We hope that this text will make problem solving on computers an exciting
and rewarding endeavor, and that you will find computer programming a fun
experience. We appreciate receiving suggestions for improvements and ideas
for additional illustrative examples and exercises.
Acknowledgments
We have been fortunate to have had the advise and criticism of many talented
people who reviewed earlier drafts of this book. In particular, we would like to
mention Stephen J. Allan, Utah State University; Eric P. Bloom, Bentley College;
John L. Carroll, San Diego State University; John Crenshaw, Western Kentucky
University; Grady Early, Southwest Texas State University; Maurice L. Eggen,
Trinity University; Rhonda Ficek, Moorhead State University; Robert C. Gann,
Hartwick College; Gordon Hoagland, Ricks College; Peter C. Isaacson, Univer-
sity of Northern Colorado; Keith E. Jolly, Chabot College; William Jones, Cali-
fornia State University, Dominquez Hills; Lyndon Marshall, College of Great
Falls; Eric Nagler, De Anza, Mission, and Ohlone Colleges; Kenneth Pierce,
University of Mary Hardin-Baylor; Arline Sachs, Northern Virginia Commu-
nity College; Peter Schleppenbach, Los Angeles Pierce College; and Jack van
Luik, Mount Hood Community College.
We have had a pleasant relationship with West. Rick Mixter believed in this
project from day one and kept us focused on students. Keith Dodson put in a
great deal of effort in bringing this project to fruition. Tom Modi enthusiasti-
cally experimented with many new ideas in the production of this book. Mar-
tha Knutson helped us smooth many language wrinkles. Liz Grantham was
instrumental in the promotion of the book. We thank them and others at West.
PREFACE xiii
This book would not have completed without the support and patience of
our family. They are the ones who had to constantly endure our "Not this
weekend, I have to work on the book" answers.
Ram Kumar
Rakesh Agrawal
