C89 has this language in §3.1.2.5 Types: A computation involving unsigned operands can never overflow, because a result that cannot be represented by the

C89 has this language in §3.1.2.5 Types: A computation involving unsigned operands can never overflow, because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting unsigned integer type.