The ANSI C standard defines a set of functions, as well as related types and macros, to be provided with any implementation of ANSI C. This chapter lists and briefly describes the ANSI-conformant library features common to all DEC C platforms. See your DEC C library routine documentation for a detailed description of these routines and their use in your system environment, and for additional headers, functions, types, and macros that may be available on your operating system.
All library functions are declared in a header file.
To make the contents of a header file available to your program,
include the header file with an #include preprocessor
directive. For example:
#include <stddef.h>
Each header file declares a set of related functions, as well as defining any types and macros needed for their use.
The standard headers are:
<assert.h> (Section 9.1)
<ctype.h> (Section 9.2)
<errno.h> (Section 9.3)
<limits.h> and
<float.h> (Section 9.4)
<locale.h> (Section 9.5)
<math.h> (Section 9.6)
<setjmp.h> (Section 9.7)
<signal.h> (Section 9.8)
<stdarg.h> (Section 9.9)
<stddef.h> (Section 9.10)
<stdio.h> (Section 9.11)
<stdlib.h> (Section 9.12)
<string.h> (Section 9.13)
<time.h> (Section 9.14)
Header files can be included in any order. Each can be
included more than once in a given scope with no effect
different from being included once. However, the effect of
including <assert.h> depends on the definition of
NDEBUG . Include headers outside of any external
declaration or definition, and before any reference to the
functions, types, or macros declared or defined in the headers.
If an identifier is declared or defined in more than one included
header, the second and subsequent headers containing that identifier
can be included after the initial reference to that identifier.