Defining and Calling Functions

Functions allow us to break a program into smaller, reusable parts.

In this lesson, you will learn how to:

• Define and call functions.
• Use function parameters and return values.
• Write modular and efficient code.

A function is a block of code that performs a specific task.

Functions improve code readability, reusability, and organization.

Example syntax:

returnType functionName(parameters) { // Function body }

This program defines a function that prints a message.

#include <stdio.h>

void greet() {
    printf("Hello from a function!\n");
}

int main() {
    greet();
    return 0;
}

Functions can accept input values, called parameters.

Example:

void greetUser(char name[]) { printf("Hello, %s!\n", name); }

This program defines a function that greets a user by name.

#include <stdio.h>

void greetUser(char name[]) {
    printf("Hello, %s!\n", name);
}

int main() {
    greetUser("Alice");
    return 0;
}

Functions can return values using the return statement.

Example:

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

This program adds two numbers and returns the result.

#include <stdio.h>

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

int main() {
    int result = add(5, 10);
    printf("Sum: %d\n", result);
    return 0;
}

Functions help in:

• Reducing code duplication.
• Improving readability and maintainability.
• Organizing complex programs into smaller parts.

In this lesson, you learned:

• How to define and call functions.
• How to pass parameters to functions.
• How to return values from functions.

Next, we will learn about function prototypes and variable scope in C!