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 (see below)
Program: Attachmate Extra is a 3270 emulator by Attachmate Corporation
SeeAlso: AH=A1h

Bitfields for 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

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