INT 21,44,F / IOCTL,F - Set Logical Drive

AH = 44h

AL = 0F

BL = new drive number (0=default, 1=A:, 2=B:, 3=C:, ...)

on return

AX = error code if CF set (see ~DOS ERROR CODES~)

AL = logical drive number (should be equal to BL input)

= 0 if drive accessed by only one drive specifier

= 1 if drive A:, 2 if drive B:, etc

- changes the logical drive designator of the physical drive

to be accessed next

- implemented from DOS 3.2