The type size_t is defined in the header file <stdio.h> as
    follows:

    typedef unsigned int size_t

    The reading begins at the current location in the file. The items
    read are placed in storage beginning at the location given by
    the first argument. You must also specify the size of an item, in
    bytes.

    If the file pointed to by file_ptr was opened in record mode,
    fread will read size_of_item multiplied by number_items bytes
    from the file. That is, it does not necessarily read number_items
    records.