Arithmetic operators

Learn basic arithmetic with +, -, *, / and %.

Arithmetic operators

C uses five arithmetic operators often: +, -, *, / and %. The first four are the addition, subtraction, multiplication and division you know. % gives the remainder of a division.

17 % 5  /* 2: 17 = 3*5 + 2 */
7 / 2   /* 3: integer division */

When two int values are divided the fraction is dropped; the result is still an int. Use double if you need the fraction.

Integer division

When two int values are divided the result is an int and the fraction is dropped. 7 / 2 gives 3, not 3.5. This is called integer division.

int a = 7 / 2;   /* a = 3 */
double b = 7.0 / 2.0;  /* b = 3.5 */

For a fractional result make at least one side a double. Writing the literal as 7.0 is enough.

Exercise Print five operations

Define int a = 7, b = 3;. With five printf calls print a + b, a - b, a * b, a / b and a % b on separate lines. Output should be 10, 4, 21, 2, 1.

Show example solution

#include <stdio.h>

int main(void) {
    int a = 7, b = 3;
    printf("%d\n", a + b);
    printf("%d\n", a - b);
    printf("%d\n", a * b);
    printf("%d\n", a / b);
    printf("%d\n", a % b);
    return 0;
}

Test yourself

What is the result of 17 % 5?
- 3
- 2
- 12
- 0
Show answer

2 — 17 = 3*5 + 2, so the remainder is 2.

Complete the remainder operator

int r = 17 ____ 5;  /* remainder: 2 */

Show answer

int r = 17 % 5;  /* remainder: 2 */

Match operators to their meanings

+

Addition
-

Subtraction
*

Multiplication
/

Division

Next lesson: Assignment operators

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