1.15 Standard Header Files

All function prototypes, macros, and types in the ANSI library are contained in one or more of the following standard header files:

assert.h	inttypes.h(*)	signal.h	stdlib.h
complex.h(*)	iso646.h(*)	stdarg.h	string.h
ctype.h	limits.h	stdbool.h(*)	tgmath.h(*)
errno.h	locale.h	stddef.h	time.h
fenv.h(*)	math.h	stdint.h(*)	wchar.h(*)
float.h	setjmp.h	stdio.h	wctype.h(*)

Because a standard "function" may also be implemented as a macro, your source files should contain no other declaration of a function once the appropriate header file has been included.

Table 1-22 describes some commonly used types. The table also lists which header files define each type.

Table 1-22. Commonly used types
Type	Purpose	Header files
size_t	Used to express the size of an object as a number of bytes (generally equivalent to unsigned int)	stddef.h, stdio.h
wchar_t	Used to hold multi-byte character codes, and large enough to represent the codes of all extended character sets	stdlib.h, wchar.h(*)
wint_t^(*)	An integer type used to represent wide characters, including the macro WEOF	wchar.h(*)
ptrdiff_t	Used to represent the difference of two pointers (usually equivalent to int)	stddef.h