Int 21 Fn 4404  - Stacker - Get Device Driver Address And Set Volume Numb  [d]

   AX = 4404h
   BL = drive number (00h = default, 01h = A:, etc.)
   CX = 0004h
   DS:DX -> DWORD buffer to receive device driver address

Note:  In addition to returning the address of the Stacker device driver,
     this call also sets the volume number at offset 3Eh in the device
     driver (see INT 25/AX=CDCDh)

See Also: INT 25/AX=CDCDh