Maybe they used "borrow" in the "new" method to avoid having both 2-3=9 and 2-3=-1, compared to explicit radix+2-3. But if you actually wanted to memorize subtr

Maybe they used "borrow" in the "new" method to avoid having both 2-3=9 and 2-3=-1, compared to explicit radix+2-3. But if you actually wanted to memorize subtraction table then "old" way is maybe easier, because your table is nice square grid instead of wider triangle (and if you actually need negative result you can do second lookup for 10-x). Also try doing something like 2000-1111 in "new" method and you go on huge side quest to propagate the borrows and go back to the beginning. Compared to "old" method where you progress one digit at a time without backtracking.