INT 21 - Attachmate Extra - GET 3270 DISPLAY STATE
        AH = A0h
Return: AL = display status
            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
        BX = host window status
            bit 15:  reserved
            bit 14:  0=host E window installed, 1=not
            bit 13:  0=host E terminal on, 1=off
            bit 12:  0=host E window displayed, 1=not
            bit 11:  reserved
            bit 10:  0=host D window installed, 1=not
            bit  9:  0=host D terminal on, 1=off
            bit  8:  0=host D window displayed, 1=not
            bit  7:  reserved
            bit  6:  0=host C window installed, 1=not
            bit  5:  0=host C terminal on, 1=off
            bit  4:  0=host C window displayed, 1=not
            bit  3:  reserved
            bit  2:  0=host B window installed, 1=not
            bit  1:  0=host B terminal on, 1=off
            bit  0:  0=host B window displayed, 1=not
Note:   Attachmate Extra is a 3270 emulator by Attachmate Corporation