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: INT 2F/AX=122Bh

See also: 21440F

21440E - DOS 3.2+ - IOCTL - GET LOGICAL DRIVE MAP