Int 21/AX=4400h

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INT 21 - DOS 2+ - IOCTL - GET DEVICE INFORMATION
AX = 4400h
BX = handle

Return:
CF clear if successful DX = device information word (see #01423) AX destroyed CF set on error AX = error code (01h,05h,06h) (see #01680 at AH=59h/BX=0000h)

Notes: Value in DH corresponds to high byte of device driver's attribute word if handle refers to a character device. Novell NetWare reportedly does not return a drive number in bits 5-0 for a disk file. This function was not supported by Digital Research's DOS Plus

See Also: AX=4401h - INT 2F/AX=122Bh

Bitfields for device information word: Bit(s) Description (Table 01423) character device 14 device driver can process IOCTL requests (see AX=4402h"DOS 2+") 13 output until busy supported 11 driver supports OPEN/CLOSE calls 8 ??? (set by MS-DOS 6.2x KEYB) 7 set (indicates device) 6 EOF on input 5 raw (binary) mode 4 device is special (uses INT 29) 3 clock device 2 NUL device 1 standard output 0 standard input disk file 15 file is remote (DOS 3.0+) 14 don't set file date/time on closing (DOS 3.0+) 11 media not removable 8 (DOS 4 only) generate INT 24 if no disk space on write or read past end of file 7 clear (indicates file) 6 file has not been written 5-0 drive number (0 = A:)

See Also: INT 29

Category: DOS Kernel - Int 21h - @

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