Return values
- C course
- Beginner
- Lesson 66/116
- 4 min
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.
Practice 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.
Starter code
#include <stdio.h>
/* define square function */
int main(void) {
/* call printf %d with square(4) */
return 0;
}Sample solution
#include <stdio.h>
int square(int x) {
return x * x;
}
int main(void) {
printf("%d\n", square(4));
return 0;
}Expected output
16
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 return expression
int square(int x) {
return ____;
}int square(int x) {
return x * x;
}Explanation: Answer is x * x. The square is x times x.
2 Which return statement can a void function use?
- return 5;
- return x + y;
- return; Correct answer
- return "text";
Explanation: A void function can only early-exit with return;.
3 Match return types
| Term | Meaning |
|---|---|
int |
returns integer |
void |
no return value |
char |
returns character |
double |
returns decimal |