Functions in C

Functions in C are blocks of code that perform a specific task. Instead of writing the same code multiple times, we can create a function and call it whenever needed.

Types of Functions in C

1. Library Functions (Predefined Functions)

These are functions already defined in C's standard library. Examples:
printf() - Prints output to the screen
scanf() - Takes user input
sqrt() - Calculates square root

Example 1:

#include <stdio.h>
#include <math.h> // Required for sqrt()

int main() {
    int num = 81;
    printf("Square root of %d is %.2f", num, sqrt(num));
    return 0;
}

Output:

Square root of 81 is 9.00

User-Defined Functions:

These are functions created by the user for specific tasks.

Types of User-defined

1. Functions with No Arguments & No Return Value
Functions with No Arguments & No Return Value

2. Functions with Arguments but No Return Value
Takes parameters but does not return a value

3. Functions with No Arguments but Returns a Value
Does not take parameters but returns a value

4. Functions with Arguments & Returns a Value
Takes parameters and returns a value

Where Do We Use Functions in Real Life?

Functions are used everywhere in programming, from games to web applications.

Example : Functions in a Video Game

Imagine you’re developing a 2D platformer game where a player controls a character. You need functions for different actions:

🔹moveLeft()→ Move the character left
🔹moveRight()→ Move the character right
🔹moveJump()→ Move the character jump
🔹moveSlide()→ Move the character slide

void moveLeft() {
printf("Character moved left\n");
}

void moveRight() {
    printf("Character moved right\n");
}

void jump() {
    printf("Character jumped\n");
}

void attack() {
    printf("Character attacked\n");
}

int main() {
    moveLeft();
    moveRight();
    jump();
    attack();
    return 0;
}

Example: Functions in an ATM System

Think about how an ATM machine works. It has different operations that need to be repeated for multiple users.

🔹withdrawMoney() → Handles cash withdrawals
🔹dipositMoney() → Allow deposits
🔹checkBalance() → Displays current account balance

Why Are Functions Important?

Avoid Repetition ✖️ : Instead of writing the same code multiple times, we use functions.
Easy Debugging 🛠️: If something goes wrong, we fix it in one place instead of searching everywhere.
Better Code Organization 📂: Helps in structuring large projects like games, banking software, and websites.