Some functions, macros, variables and types may be found in more that one or two standard headers. These are listed below.
Description
The value of a null pointer constant.
Include
<locale.h>
<stddef.h>
<stdio.h>
<stdlib.h>
<string.h>
<time.h>
Description
The result type of the sizeof operator.
Include
<stddef.h>
<stdio.h>
<stdlib.h>
<string.h>
<time.h>