0:471h                   Break Key State

 Length: 1 byte

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

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       Notes:         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.