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 <cstdio>, it is used as the type of some parameters in the functions fread, fwrite and setvbuf, and in the case of fread and fwrite also as its returning type.