C Programming Function Arguments And Return Values Complete Guide

Example 1: Function with No Arguments and No Return Value

In this example, we create a simple function that prints "Hello, World!".

#include <stdio.h>

// Function declaration
void printMessage();

int main() {
    // Calling the function
    printMessage();
    return 0;
}

// Function definition
void printMessage() {
    printf("Hello, World!\n");
}

Explanation:

• Function Declaration: void printMessage(); tells the compiler that there is a function named printMessage which does not take any arguments and does not return any value (void).
• Function Definition: void printMessage() { printf("Hello, World!\n"); } is the actual implementation of the function.
• Function Call: printMessage(); inside the main function calls the printMessage function to perform its operation.

Example 2: Function with Arguments and No Return Value

Now, let's create a function that takes two integers as arguments and prints their sum.

#include <stdio.h>

// Function declaration
void printSum(int num1, int num2);

int main() {
    int a = 5, b = 3;
    // Calling the function with arguments
    printSum(a, b);
    return 0;
}

// Function definition
void printSum(int num1, int num2) {
    int sum = num1 + num2;
    printf("Sum: %d\n", sum);
}

Explanation:

• Function Declaration: void printSum(int num1, int num2); specifies that the function printSum takes two integers as parameters and does not return a value.
• Function Definition: void printSum(int num1, int num2) defines the function's operation, which computes and prints the sum of the arguments.
• Function Call: printSum(a, b); passes the variables a and b to the printSum function.

Example 3: Function with Arguments and a Return Value

In this example, we'll write a function that returns the product of two integers.

#include <stdio.h>

// Function declaration
int multiply(int num1, int num2);

int main() {
    int x = 4, y = 6;
    // Calling the function and storing the return value
    int result = multiply(x, y);
    printf("Product: %d\n", result);
    return 0;
}

// Function definition
int multiply(int num1, int num2) {
    return num1 * num2;
}

Explanation:

• Function Declaration: int multiply(int num1, int num2); declares that the function multiply takes two integers as arguments and returns an integer.
• Function Definition: int multiply(int num1, int num2) performs the multiplication and returns the result using the return statement.
• Function Call: int result = multiply(x, y); calls the function and stores the returned value in the variable result.

Example 4: Function with Multiple Return Values Using Pointers

C does not support functions returning multiple values directly, but we can achieve this by using pointers to modify the values outside the function.

#include <stdio.h>

// Function declaration
void getMinMax(int arr[], int size, int *min, int *max);

int main() {
    int numbers[] = {3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5};
    int min, max;

    // Calling the function with array and pointer addresses
    getMinMax(numbers, 11, &min, &max);

    printf("Minimum Value: %d\n", min);
    printf("Maximum Value: %d\n", max);

    return 0;
}

// Function definition
void getMinMax(int arr[], int size, int *min, int *max) {
    *min = arr[0];
    *max = arr[0];

    for (int i = 1; i < size; i++) {
        if (arr[i] < *min) {
            *min = arr[i];
        }
        if (arr[i] > *max) {
            *max = arr[i];
        }
    }
}

Explanation:

• Function Declaration: void getMinMax(int arr[], int size, int *min, int *max); declares that the function takes an integer array, its size, and two pointers to integers (min and max).
• Function Definition: void getMinMax iterates through the array to find the minimum and maximum values, updating the values pointed to by min and max.
• Function Call: getMinMax(numbers, 11, &min, &max); passes the array and the addresses of min and max to the function. After the function call, min and max contain the minimum and maximum values of the array.

Example 5: Recursive Function

We will create a recursive function to calculate the factorial of a number.