Return values

Learn to return a value from a function with return.

Returning values with return

A function can send a value back to the caller with the return keyword. The return type sets the type of the value.

int add(int a, int b) {
    return a + b;
}

int result = add(3, 5);  /* result = 8 */

When return runs, the function ends and the value goes back to the caller. void functions return no value; they can only early-exit with return;.

Using the return value

You can assign a function's return value to a variable or use it directly in an expression.

int result = add(3, 5);
printf("%d\n", add(2, 4));  /* prints 6 */
int bigger = add(1, 1) > add(0, 0);

It is also fine to ignore the value: add(3, 5); computes the result but does not store it. If the function has side effects (like printf), this still matters.

Exercise Square of a number

Define int square(int x) with body return x * x;. Call printf("%d\n", square(4)); from main. Output should be 16.

Show example solution

#include <stdio.h>

int square(int x) {
    return x * x;
}

int main(void) {
    printf("%d\n", square(4));
    return 0;
}

Test yourself

return expression

int square(int x) {
    return ____;
}

Show answer

int square(int x) {
    return x * x;
}

Which return statement can a void function use?
- return 5;
- return x + y;
- return;
- return "text";
Show answer

return; — A void function can only early-exit with return;.
Match return types

int

returns integer
void

no return value
char

returns character
double

returns decimal

Next lesson: Parameters

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