Forget about for statements for a second and let's write both a counting up and a counting down loop using while statements. // count up std::size_t i

Forget about for statements for a second and let's write both a counting up and a counting down loop using while statements. // count up std::size_t i = 0; while (i != 10) { std::cout << i << "\n"; ++i; } // count down std::size_t i = 10; while (i != 0) { --i; std::cout << i << "\n"; } After initialization a for statement repeats "test; body; advance", this is ideal for counting up loops, but what we need for counting down loops is "test; advance; body". Since C/C++ do not provide the latter as a primitive you have to use a while loop as shown above. Using a signed integer to shoehorn a counting down loop into a for statement at the cost of 1/2 your range is a hack IMO. Note that when working with iterators you have to resort to a while statement as iterating past begin is UB.