INT 21 - Attachmate Extra - SET HOST WINDOW STATE
        AH = A2h
        AL = set status byte
            bit  7  : 0=power off, 1=power on
            bit  6  : 0=not installed, 1=installed
            bits 5-3: reserved
            bits 2-0: window number 1-4=host B-E
SeeAlso: AH=A1h

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