Return Values

Functions in C can send back a value to the code that called them. This is called a return value.

Function Return Types

Every function in C has a return type that specifies what kind of value it will return:

int add(int a, int b) {
    return a + b;  // Returns an integer
}

float divide(float x, float y) {
    return x / y;  // Returns a float
}

char getGrade(int score) {
    if (score >= 90) return 'A';
    else if (score >= 80) return 'B';
    else return 'C';  // Returns a character
}

The return Statement

The return statement is used to send a value back from a function:

#include <stdio.h>

int multiply(int x, int y) {
    int result = x * y;
    return result;  // Send back the result
}

int main() {
    int answer = multiply(5, 3);  // answer gets the value 15
    printf("5 x 3 = %d\n", answer);
    return 0;
}

Functions Without Return Values (void)

Some functions don't need to return anything - they just perform an action. These use the void return type:

void printMessage() {
    printf("Hello, World!\n");
    // No return statement needed (or just 'return;')
}

void displayMenu() {
    printf("1. Start Game\n");
    printf("2. Settings\n");
    printf("3. Exit\n");
    return;  // Optional for void functions
}

Using Return Values

You can use return values in different ways:

#include <stdio.h>

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

int main() {
    // Store in a variable
    int result = square(4);
    printf("Square of 4 is %d\n", result);
    
    // Use directly in expressions
    int sum = square(3) + square(4);  // 9 + 16 = 25
    printf("Sum of squares: %d\n", sum);
    
    // Use in conditions
    if (square(5) > 20) {
        printf("25 is greater than 20!\n");
    }
    
    return 0;
}

Multiple Return Statements

A function can have multiple return statements, but only one will execute:

int findMax(int a, int b) {
    if (a > b) {
        return a;  // Exit here if a is larger
    }
    return b;      // Exit here if b is larger or equal
}

char checkSign(int number) {
    if (number > 0) return '+';
    if (number < 0) return '-';
    return '0';  // number is zero
}

Important Notes

• Once a return statement executes, the function immediately exits
• The returned value must match the function's return type
• main() function typically returns 0 to indicate successful program execution
• If a non-void function doesn't return a value, the behavior is undefined