It's even worse than most people seem to realize. For many years the ISO standard for C included the line: "If both operands are nonnegative then the remainder

It's even worse than most people seem to realize. For many years the ISO standard for C included the line: "If both operands are nonnegative then the remainder is nonnegative; if not, the sign of the remainder is implementation-defined" Fortunately, this was changed at some point between C '99 and C '11, so that now the remainder is consistently defined across all implementations.