Closing Files: During a write to a file, the data written is not put on the disk immediately. It is stored in a buffer. When the buffer is full, all its contents are actually written to the disk. The process of emptying the buffer by writing its contents to disk is called flushing the buffer. Losing the file flushes the buffer and releases the space taken by the FILE structure which is returned by fopen. For this fclose () function is used.
fclose (File * stream (s);