INT 21,44,1 / IOCTL,1 - Set Device Information
AH = 44h
AL = 01
BX = handle
DH = must be zero
DL = device data low order byte (see below)
on return
AX = error code if CF set
DX = device information (see below)
- applicable to character devices only
- allows setting of device data word for character devices
- usually used to change from binary to translated I/O
- handle in BX must be an opened file or device
Device Data Word
│F│E│D│C│B│A│9│8│7│6│5│4│3│2│1│0│ Device Data Word
│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ └──── 1 = standard input device
│ │ │ │ │ │ │ │ │ │ │ │ │ │ └──── 1 = standard output device
│ │ │ │ │ │ │ │ │ │ │ │ │ └──── 1 = NUL device
│ │ │ │ │ │ │ │ │ │ │ │ └──── 1 = clock device
│ │ │ │ │ │ │ │ │ │ │ └──── reserved
│ │ │ │ │ │ │ │ │ │ └──── 1 = binary mode, 0 = translated
│ │ │ │ │ │ │ │ │ └──── 0 = end of file on input
│ │ │ │ │ │ │ │ └──── 1 = character device
└─┴─┴─┴─┴─┴─┴─┴──── reserved, must be zero