AH = 44h AL = 09 BL = drive number (0=default, 1=A:, 2=B:, 3=C:, ...) on return AX = error code if CF set (see DOS ERROR CODES) DX = device attribute word bit 12 = 1 if drive is remote bit 12 = 0 if drive is local - used to determine if block device is local or remote - returns invalid function if networking not started - implemented from DOS 3.1