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214409

Category: DOS kernel

INT 21 - 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
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh

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  Copyright 2000   by Ralf Brown     Updated Jul 2000