[uecker]

The C89 standard has "A computation involving unsigned operands can never overflou. because a result that cannot be represented b! the resulting unsigned integer type is reduced modulo the number that is one greater thnn the largest value that can be represented by the resulting unsipned integer type" (OCR errors) You can finde a copy here: https://web.archive.org/web/20200909074736if_/https://www.pd...

Mathematically, there is no clearly defined way how one would have to map from one residue system in modular arithmetic to the next, so there is no "correct" or "incorrect" way. Mapping to the smallest integer in the equivalency class makes a lot of sense though, as it maps corresponding integers to itself when going to a larger type and and the reverse operation is then the inverse, and this is exactly what C does.