AH = 33h
        AL = subfunction
            00h Get
            01h Put
               DL = 0 for OFF or 1 for ON
            02h internal, called by PRINT.COM (DOS 3.1)
Return: DL = current BREAK setting if AL = 00h
            0 BREAK=OFF
            1 BREAK=ON
        AL = FFh if error
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