def optimize_bit_format(bits_size):
    """
    By default, C types are represented in the machine’s native format and byte
    order. Alternatively, the first character of the format string can be used
    to indicate the byte order, size and alignment of the packed data.
    ~~~
    @params bits_size : Decimal integer.
    @return fmt_code  : Format codes means the conversion between C and Python values.
                        Ref: https://docs.python.org/3/library/struct.html#format-characters
    @return std_size  : Refers to the size of the packed value in bytes when using standard size.
    """
    if bits_size >= 1 << 31:
        fmt_code, std_size = 'Q', 8
    elif bits_size >= 1 << 15:
        fmt_code, std_size = 'I', 4
    else:
        fmt_code, std_size = 'H', 2
    return fmt_code, std_size
