Return values

Learn to return a value from a function with return.

Returning values with return

A function can send a value back to its caller. The definition int add(int a, int b) { return a + b; } returns the sum to the caller. The return keyword exits the function and gives the value back.

The return type can be any type: int, double, std::string and so on. The void return type means 'returns nothing'; in such functions return may be written without a value or omitted. You can store the returned value or use it directly: int s = add(2, 3);.

void functions

A function does not have to return a value. The void return type marks a function that performs a side effect without computing anything: it prints, writes to a file or changes state.

In void printHello() { std::cout << "hi"; } there is no return. You may write return; (no value) but it is not required; the function ends on its own at the closing brace. You cannot store the call in a variable: int x = printHello(); is a compile error.

Exercise Write square and call it

Define an int square(int x) function that returns x*x. In main, call square(6) and print the result with std::cout.

Show example solution

#include <iostream>

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

int main() {
    std::cout << square(6) << std::endl;
    return 0;
}

Test yourself

Complete the return statement

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

Show answer

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

For int square(int x) { return x*x; } what does square(5) return?
```
int square(int x) { return x*x; }
```
- 5
- 10
- 25
- 0
Show answer

25 — square(5) calls with x=5, returning 5*5 = 25.
Match the return types

int

Returns an integer
double

Returns a decimal
void

Returns nothing
std::string

Returns text

Next lesson: Parameters

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