Standard C++ Library Reference ISO/IEC (VERSION3)

If all elements are equal, the function returns zero.●
If the differing element from s1 is greater than the element from s2, the function returns
a positive number.
●
Otherwise, the function returns a negative number.●
memcpy
void *memcpy(void *s1, const void *s2, size_t n);
The function copies the array of char beginning at the address s2 to the array of char beginning
at the address s1 (both of size n). It returns s1. The elements of the arrays can be accessed and
stored in any order.
memmove
void *memmove(void *s1, const void *s2, size_t n);
The function copies the array of char beginning at s2 to the array of char beginning at s1 (both
of size n). It returns s1. If the arrays overlap, the function accesses each of the element values
from s2 before it stores a new value in that element, so the copy is not corrupted.
memset
void *memset(void *s, int c, size_t n);
The function stores (unsigned char)c in each of the elements of the array of unsigned
char beginning at s, with size n. It returns s.
NULL
#define NULL <either 0, 0L, or (void *)0> [0 in C++]
The macro yields a null pointer constant that is usable as an address constant expression.
size_t
typedef ui-type size_t;
The type is the unsigned integer type ui-type of an object that you declare to store the result
of the sizeof operator.