def pformat_program_dump(self, program_dump, program_start=None):
        """
        format a BASIC program dump. Useful for debugging.
        returns a list of formated string lines.
        """
        assert isinstance(program_dump, bytearray)

        if program_start is None:
            program_start = self.DEFAULT_PROGRAM_START
        return self.listing.pformat_program_dump(program_dump, program_start)