Int 21/AX=4409h

DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE

AX = 4409h
BL = drive number (00h = default, 01h = A:, etc)

Return:
CF clear if successful
DX = device attribute word
bit 15:
Drive is SUBSTituted
bit 13:
(DR DOS 3.41/5.0 local drives only) always set
media ID needed
bit 12:
Drive is remote
bit  9:
Direct I/O not allowed.
CF set on error
AX = error code (01h,0Fh,15h) (see #01680 at AH=59h/BX=0000h)

Notes: On local drives, DX bits not listed above are the attribute word from the device driver header (see #01646 at AH=52h); for remote drives, the other bits appear to be undefined for MS-DOS versions prior to 5.0 (they are all cleared in DOS 5+). Checking whether DX=0800h on return appears to be a fairly reliable method for detecting Microsoft's RAMDRIVE, though not for other ramdisks (there appears to be no simple yet foolproof method for detecting ramdisks, although the presence of only a single copy of the FAT and only a single head on non-removable devices is a fairly good indicator); for Windows95, RAMDRIVE returns DX=4800h. For non-existent remote drives, this function sometimes returns AX=0015h (drive not ready) instead of AX=000Fh (invalid drive) on the first call; a subsequent call will return the correct error code. This function was not supported by Digital Research's DOS Plus

See Also: AX=4400h - AX=4408h - AX=440Ah - INT 2F/AX=122B

Category: DOS Kernel - Int 21h - D

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