Division and modulo operations are susceptible to divide-by-zero errors. According to section 6.5.5, paragraph 5 of \[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] (see also [undefined behavior 42 | CC. Undefined Behavior#ub_42] of Annex J):

The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined.

Division

The result of the / operator is the quotient from the division of the first arithmetic operand by the second arithmetic operand. Division operations are susceptible to divide-by-zero errors. Overflow can also occur during two's complement signed integer division when the dividend is equal to the minimum (negative) value for the signed integer type and the divisor is equal to —1 (see INT32-C. Ensure that operations on signed integers do not result in overflow).

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