type
<cstddef> <cstdio> <cstdlib> <cstring> <ctime> <cwchar>
size_t
Unsigned integral type
Alias of one of the fundamental unsigned integer types.
It is a type able to represent the size of any object in bytes: size_t is the type returned by the sizeof operator and is widely used in the standard library to represent sizes and counts.
In <cstring>, it is used as the type of the parameter num in the functions memchr, memcmp, memcpy, memmove, memset, strncat, strncmp, strncpy and strxfrm, which in all cases it is used to specify the maximum number of bytes or characters the function has to affect.
It is also used as the return type for strcspn, strlen, strspn and strxfrm to return sizes and lengths.