Between C89 and C99, the standard was updated to require integer division to truncate towards 0. C99 draft standard: http://www.open-std.org/jtc1/sc22/wg14/www

Between C89 and C99, the standard was updated to require integer division to truncate towards 0. C99 draft standard: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf PDF page 94, physical page 82, “When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded.” with a footnote: “This is often called ‘‘truncation toward zero’’” I wish % was a modulo instead of a remainder operation; this bug has bitten me more than once.