Interesting. Given that you work with an 8 bits processor, base 100 could have been an option too. But now I am getting quite puzzled as I believe that multiple carries are not possible: when you double a digit, this can cause a carry-out; in all cases you get an even digit, at most Base-2; for the same digit, the carry-in cannot cause an extra carry-out. Said differently, the doubling of digits generates all the carries-out it needs to, and my original algorithm is correct. On the opposite, merely reversing the traversal direction causes all carries-out to be unduly doubled.
