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ptrdiff_t is the result of
subtracting two pointers.
size_t is the unsigned integer result of
the sizeof keyword.
wchar_t is an integer type of the size
of a wide character constant.
NULL is the value of a null pointer
constant.
offsetof(type,
member-designator)
This results in a constant integer of type
size_t which is the offset in bytes of a
structure member from the beginning of the structure. The
member is given by member-designator, and the name of
the structure is given in type.
Example:
#include<stddef.h>
#include<stdio.h>
int main(void)
{
struct user{
char name[50];
char alias[50];
int level;
};
printf("level is the %d byte in the user structure.\n"),
offsetof(struct user,level));
}
The output should be:
level is the 100 byte in the user structure.
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