Preface
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 machineindependent 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 crosschecking 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 machinedependent.
This second edition of The C Programming Language
describes C as defined by the ANSI standard. Although we have noted
the places where the language has evolved, we have chosen to write
exclusively in the new form. For the most part, this makes no
significant difference; the most visible change is the new form of
function declaration and definition. Modern compilers already
support most features of the standard.
We have tried to retain the brevity of the first edition. C is
not a big language, and it is not well served by a big book. We
have improved the exposition of critical features, such as
pointers, that are central to C programming. We have refined the
original examples, and have added new examples in several chapters.
For instance, the treatment of complicated declarations is
augmented by programs that convert declarations into words and vice
versa. As before, all examples have been tested directly from the
text, which is in machinereadable form.
Appendix A, the reference manual, is not the standard, but our
attempt to convey the essentials of the standard in a smaller
space. It is meant for easy comprehension by programmers, but not
as a definition for compiler writersÑ that role properly belongs to
the standard itself. Appendix B is a summary of the facilities of
the standard library. It too is meant for reference by programmers,
not implementers. Appendix C is a concise summary of the changes
from the original version.
As we said in the preface to the first edition, C "wears well as
one's experience with it grows." With a decade more experience, we
still feel that way. We hope that this book will help you to learn
C and to use it well.
Brian W. Kernighan, Dennis M.
Ritchie
Preface to the First Edition
C is a generalpurpose programming language which features
economy of expression, modern control flow and data structures, and
a rich set of operators. C is not a "very high level" language, nor
a "big" one, and is not specialized to any particular area of
application. But its absence of restrictions and its generality
make it more convenient and effective for many tasks than
supposedly more powerful languages.
C was originally designed for and implemented on the UNIX
operating system on the DEC PDP1 1, by Dennis Ritchie. The
operating system, the C compiler, and essentially all UNIX
applications programs (including all of the software used to
prepare this book) are written in C. Production compilers also
exist for several other machines, including the IBM System/370, the
Honeywell 6000, and the Interdata 8/32. C is not tied to any
particular hardware or system, however, and it is easy to write
programs that will run without change on any machine that supports
C.
This book is meant to help the reader learn how to program in C.
It contains a tutorial introduction to get new users started as
soon as possible, separate chapters on each major feature, and a
reference manual. Most of the treatment is based on reading,
writing and revising examples, rather than on mere statements of
rules. For the most part, the examples are complete, real programs,
rather than isolated fragments. All examples have been tested
directly from the text, which is in machinereadable form. Besides
showing how to make effective use of the language, we have also
tried where possible to illustrate useful algorithms and principles
of good style and sound design.
The book is not an introductory programming manual; it assumes
some familiarity with basic programming concepts like variables,
assignment statements, loops, and functions. Nonetheless, a novice
programmer should be able to read along and pick up the language,
although access to a more knowledgeable colleague will help.
In our experience, C has proven to be a pleasant, expressive,
and versatile language for a wide variety of programs. It is easy
to learn, and it wears well as one's experience with it grows. We
hope that this book will help you to use it well.
Brian W. Kernighan, Dennis M.
Ritchie