Int 21 Fn 6B  U - DOS 4.0 Internal - Ifs Ioctl                             [D]

   AH = 6Bh
   AL = subfunction
       00h ???
       DS:SI -> Current Directory Structure???
       CL = drive (1=A:)
       01h ???
       DS:SI -> ???
       CL = file handle???
       02h ???
       DS:SI -> Current Directory Structure???
       DI = ???
       CX = drive (1=A:)

Return: CF set on error
       AX = error code (see INT 21/AH=59h)
   CF clear if successful

Note:  passed through to INT 2F/AX=112Fh with AX on top of stack

See Also: AH=6Bh"DOS 5",INT 2F/AX=112Fh