Kernighan Brian W. - C Programming Language (2nd Edition)

The second edition of The C Programming Language was published early in 1988. At that time, the first C standard was almost complete, formalizing and codifying the precise definition of the language. There have been two revisions to the standard since then, in 1999 and 2011, that added a number of language features and cleared up a few minor issues. But for many programmers, the 1988 definition of C covers the parts of the language that they use, so it has never seemed necessary to update the book itself to track the newer standards. Thus, the digital version is intentionally identical to the print edition.

On the other hand, the computing world is very different from what it was in 1988. The Internet has gone from a network primarily for researchers at universities to a universal network linking everyone on the planet. Computers have continued to get smaller, cheaper, and faster; a typical laptop or cell phone today has more computing power than a supercomputer of 1988, yet costs so little that probably half the people in the world have one. Languages such as C++, Objective-C, Java, and JavaScript make it easier to program these systems as well; all of them borrow heavily from C.

Remarkably, in spite of all of this change, C retains a central position. It is still the core language for operating system implementation and tool building. It remains unequaled for portability, efficiency, and ability to get close to the hardware when necessary. C has sometimes been called a high-level assembler, and this is not a bad characterization of how well it spans the range from intricate data structure and control flow to the lowest level of external devices.

Sadly, Dennis Ritchie, the creator of C and the coauthor of this book, died in October 2011 at the age of 70 and never saw this digital edition. Dennis was a great language designer and programmer, and a superb writer, but he was also funny, warm, and exceptionally kind. We are all in his debt. He will be greatly missed.

Brian Kernighan
Princeton, New Jersey
November 2012

* Note: Example code can now be downloaded by visiting www.informit.com/store/c-programming-language-9780131103627.

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The editorial team at Prentice Hall PTR
November 2012

Second Edition

Brian W. Kernighan Dennis M. Ritchie

AT&T Bell Laboratories
Murray Hill, New Jersey

Prentice Hall PTR, Upper Saddle River, New Jersey 07458

Library of Congress Cataloging-in-Publication Data

Kernighan, Brian W.
The C programming language.
Includes index.
1. C (Computer program language) I. Ritchie,
Dennis M. II. Title.
QA76.73.C15K47 1988 005.133 88-5934
ISBN 0-13-110370-9
ISBN 0-13-110362-8 (pbk.)

Copyright 1988, 1978 by Bell Telephone Laboratories, Incorporated.

Published by Prentice Hall PTR
Prentice-Hall, Inc.
Upper Saddle River, NJ 07458

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Published simultaneously in Canada.

UNIX is a registered trademark of AT&T.

This book was typeset (pictbleqntroff -ms) in Times Roman and Courier by the authors, using an Autologic APS-5 phototypesetter and a DEC VAX 8550 running the 9th Edition of the UNIX operating system.

Prentice Hall Software Series
Brian Kernighan, Advisor

ISBN 0-13-110362-8

Text printed in the United States on recycled paper at Courier in Westford, Massachusetts.

Forty-ninth printing, January 2012

ISBN 0-13-110362-8 {PBK}
ISBN 0-13-110370-9

Prentice-Hall International (UK) Limited, London
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Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro

The computing world has undergone a revolution since the publication of The C Programming Language in 1978. Big computers are much bigger, and personal computers have capabilities that rival the mainframes of a decade ago. During this time, C has changed too, although only modestly, and it has spread far beyond its origins as the language of the UNIX operating system.

The growing popularity of C, the changes in the language over the years, and the creation of compilers by groups not involved in its design, combined to demonstrate a need for a more precise and more contemporary definition of the language than the first edition of this book provided. In 1983, the American National Standards Institute (ANSI) established a committee whose goal was to produce an unambiguous and machine-independent definition of the language C, while still retaining its spirit. The result is the ANSI standard for C.

The standard formalizes constructions that were hinted at but not described in the first edition, particularly structure assignment and enumerations. It provides a new form of function declaration that permits cross-checking of definition with use. It specifies a standard library, with an extensive set of functions for performing input and output, memory management, string manipulation, and similar tasks. It makes precise the behavior of features that were not spelled out in the original definition, and at the same time states explicitly which aspects of the language remain machine-dependent.

This second edition of The C Programming Language