ptr

    A pointer to the location, within memory, where you place the
    information being read. The type of the object pointed to is
    determined by the type of the item being read.

 size_of_item

    The size of the items being read, in bytes.

 number_items

    The number of items to be read.

 file_ptr

    A pointer that indicates the file from which the items are to be
    read.