🚀 go-pugleaf

In article <$d4Hl83l@cs.psu.edu> melling@cs.psu.edu (Michael D Mellinger) writes:
}Is there a way to avoid the "Insert disk in B drive message..." when I
}change the A drive to B from within my MS C(6.0) program on a single
}floppy system?  Right now it always prompts the user to insert a disk

There is a DOS call for DOS 3.2 and up.  For earlier versions, you'll need to
poke a byte in low memory (0050h:0004h if memory serves).

INT 21 - DOS 3.2+ - IOCTL - GET LOGICAL DRIVE MAP
        AX = 440Eh
        BL = drive number (00h=default,01h=A:,etc)
Return: CF set on error
            AX = error code (01h,0Fh) (see AH=59h)
        CF clear if successful
            AL = 00h block device has only one logical drive assigned
                 1..26 the last letter used to reference the drive (1=A:,etc)
SeeAlso: AX=440Fh,INT 2F/AX=122Bh
----------21440F-----------------------------
INT 21 - DOS 3.2+ - IOCTL - SET LOGICAL DRIVE MAP
        AX = 440Fh
        BL = physical drive number (00h=default,01h=A:,etc))
Return: CF set on error
            AX = error code (01h,0Fh) (see AH=59h)
        CF clear if successful
            drive now responds to next logical drive number
Note:   maps logical drives to physical drives, similar to DOS's treatment of
          a single physical floppy drive as both A: and B:
SeeAlso: AX=440Eh,INT 2F/AX=122Bh
-- 
{backbone}!cs.cmu.edu!ralf  ARPA: RALF@CS.CMU.EDU   FIDO: Ralf Brown 1:129/53
BITnet: RALF%CS.CMU.EDU@CARNEGIE   AT&Tnet: (412)268-3053 (school)   FAX: ask
DISCLAIMER?  Did  | It isn't what we don't know that gives us trouble, it's
I claim something?| what we know that ain't so.  --Will Rogers