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

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

Return: buffer filled with pointer into Stacker device driver (see #2238):
     driver + 19h if Stacker Anywhere controls this drive
     driver + 1Ah if Stacker controls this drive
     unchanged else

Notes: in addition to returning the address of the Stacker device driver,
     this call also sets the volume number at offset 58h in the device
     driver (see #2238 at INT 25/AX=CDCDh)
   Stacker Anywhere does not link its built-in device driver into
     the standard device driver chain, but it can be found via CDS/DPB
   this call can be used as an installation check for all versions of
     Stacker and Stacker Anywhere to avoid the INT 25 call

See Also: AX=4408h,AX=440Eh,AH=52h,INT 25/AX=CDCDh