AH = 44h AL = 06 BX = handle on return CF = 0 if successful = 1 if error AX = error code if CF set (see DOS ERROR CODES) AL = 00 if EOF (files), or not ready (char devices) = FF if not EOF (files), or ready (char devices) - used to determine if a file or device is ready for input - can be used to determine EOF unless EOF caused by INT 21,42