Introduction

1.1 Introduction

The programming language C was developed in the 1970s by Dennis Ritchie at Bell Labs (Murray Hill, New Jersey) in the process of implementing the Unix operating system on a DEC PDP-11 computer. C has its origins in the typeless programming language BCPL (Basic Combined Programming Language, developed by M. Richards) and in B (developed by K. Thompson). In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly available description of C, now known as the K&R standard.

C is a highly portable language oriented towards the architecture of today's computers. The actual language itself is relatively small and contains few hardware-specific elements. It includes no input/output statements or memory management techniques, for example. Functions to address these tasks are available in the extensive C standard library.

C's design has significant advantages:

         Source code is highly portable

         Machine code is efficient

         C compilers are available for all current systems

The first part of this pocket reference describes the C language, and the second part is devoted to the C standard library. The description of C is based on the ANSI X3.159 standard. This standard corresponds to the international standard ISO/IEC 9899, which was adopted by the International Organization for Standardization in 1990, then amended in 1995 and 1999. The ISO/IEC 9899 standard can be ordered from the ANSI web site; see http://ansi.org/public/std_info.html.

The 1995 standard is supported by all common C compilers today. The new extensions defined in the 1999 release (called "ANSI C99" for short) are not yet implemented in many C compilers, and are therefore specially labeled in this book. New types, functions, and macros introduced in ANSI C99 are indicated by an asterisk in parentheses ^(*).

1.1.1 Font Conventions

The following typographic conventions are used in this book:

Italic

Used to introduce new terms, and to indicate filenames.

Constant width

Used for C program code as well as for functions and directives.

Constant width italic

Indicates replaceable items within code syntax.

Constant width bold

Used to highlight code passages for special attention.