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2.5 Arithmetic Operators

The binary arithmetic operators are +, -, *, /, and the modulus operator %. Integer division truncates any fractional part. The expression

   x % y

produces the remainder when x is divided by y, and thus is zero when y divides x exactly. For example, a year is a leap year if it is divisible by 4 but not by 100, except that years divisible by 400 are leap years. Therefore

   if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
       printf("%d is a leap year\n", year);
   else
       printf("%d is not a leap year\n", year);

The % operator cannot be applied to a float or double. The direction of truncation for / and the sign of the result for % are machine-dependent for negative operands, as is the action taken on overflow or underflow.

The binary + and - operators have the same precedence, which is lower than the precedence of *, / and %, which is in turn lower than unary + and -. Arithmetic operators associate left to right.

Table 2.1 at the end of this chapter summarizes precedence and associativity for all operators.