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cmathc99c89integer-division

What is the behavior of integer division?

For example,

int result;

result = 125/100;

or 

result = 43/100;

Will result always be the floor of the division? What is the defined behavior?

Solution

  • Will result always be the floor of the division? What is the defined behavior?

    Not quite. It truncates toward 0, rather than flooring.

    6.5.5 Multiplicative operators

    6 When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded.88) If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a.

    and the corresponding footnote:

    1. This is often called ‘‘truncation toward zero’’.

    Of course two points to note are:

    3 The usual arithmetic conversions are performed on the operands.

    and:

    5 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.

    [Note: Emphasis mine]