Int 21 Fn A1  - Attachmate Extra - Set 3270 Display State                  [I]

   AH = A1h
   AL = set status byte
       bit  7  : 0=windowed, 1=enlarged
       bits 6-3: current screen profile number 0-9
       bits 2-0: active window number
           0=PC, 1-4=host B-E, 5-6=notepad F-G

See Also: AH=A0h,AH=A2h