0040h:0071h           Break Key State

    Length: 1 byte

    Signals whether or not the break key combination (Control-Break)
    was pressed.

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    Note
    If bit 7 of this byte is set, the break key combination was
    pressed.

    This byte is never reset to 0; hence the first instance of the
    break key combination will set bit 7 of this byte and the value of
    the byte will remain this way until the system is powered off or
    reset by the user.