Int 10 Fn 1D  - Video - Dos/v - Shift Status Line Control                  [J]

   AH = 1Dh
   AL = function
       00h enable shift status line(s)
       BX = number of lines to reserve at bottom of screen (usu. 1)
       01h disable shift status line
       BX = number of lines reserved at bottom of screen (usually 1)
       02h get number of status lines

       Return: BX = number of lines reserved for shift status

See Also: AH=19h