Function 4400h (68-0)    IOCTL: Get Device Information

Sets device information.

On entry:      AH         44h
AL         00h
BX         Device or file handle

Returns:       AX         Error code,if CF is set
DX         Device information

                                                                          

Subfunction 00h returns device information in DX. Bit 7 of DX is 1 if
the channel is a character device, and 0 if the channel is a block
device (disk file).

  DX for Character Device (Bit 7 = 1)

 Bit         Description
0          Set if standard console input device
1          Set if standard console output device
2          Set if this is a null device
3          Set if the device is a clock
4          Reserved
5          Set for binary mode, 0 for ASCII mode
6          0 if end of file (EOF) on input
7          Set to indicate a device (and not a file)
8-13         Reserved
14          Set if this device can process control strings via
subfunctions 02h, 03h, 04h, and 05h.
15          Reserved

  DX for Disk File (Bit 7 = 0)

 Bit         Description
0-5         Block device number (A = 0, B = 1, etc.)
6          Set if the channel has been written
7          0 to indicate a block device
8-13         Reserved
14          Set if this device can process control strings via
subfunctions 02h, 03h, 04h, and 05h.
15          Reserved

See also: 44h

4400h (68-0) IOCTL: Get Device Information