DESCRIPTION
 The 
<stdlib.h> header defines the following types and macros:
- 
NULL - an implementation-defined null pointer constant;
- 
size_t and wchar_t - integer types described in stddef(3);
- 
div_t, ldiv_t, and lldiv_t - structures that are returned by the div(3), ldiv(3), and lldiv(3) functions, respectively;
- 
RAND_MAX - a macro which expands to an integer constant that is the maximum value returned by the rand(3) function;
- 
MB_CUR_MAX - an integer expression of type size_t whose value is the maximum number of bytes in a character specified by the current locale; and
- 
EXIT_SUCCESS and EXIT_FAILURE - macros which expand to integer constants suitable for use as an argument to the exit(3) function.
The <stdlib.h> header also prototypes several important functions such as abort(3), atoi(3), bsearch(3), free(3), malloc(3), and strtol(3).