def int_to_bcd(integer):
    """Converts a two-digit, non-negative integer (0-99) to a one-byte
    binary coded decimal.

    :param: the integer value as a Python `int`.
    :returns: the 1-byte binary-coded decimal as a Python `int`.
    """
    assert 0 <= integer and integer <= 99
    ones = integer % 10
    tens = integer // 10
    return tens << 4 | ones
