Defining and calling functions

Defining and calling functions in C programming is a fundamental concept that allows you to break down a program into smaller, manageable tasks. Functions help in organizing code, improving code reusability, and making the program more modular. Here's how you define and call functions in C:

Function Definition:

To define a function in C, you need to provide the function prototype and the function body. The function prototype declares the function's name, return type, and parameters (if any). The function body contains the actual implementation of the function's logic.

Syntax of a function definition:

Here's an example of a function that calculates the square of a given number:

#include <stdio.h>

// Function definition for calculating the square

int square(int num) {

    int result = num * num;

    return result;

}

Function Call:

To use a function in your C program, you need to call it from the main function or any other function, depending on where you want to use it. When calling a function, you provide the required arguments (if any) in the function call.

Syntax of a function call:

Here's an example of how to call the square function from the main function:

When you run this program, it will output:

The square of 5 is 25

Function Prototype (Optional):

In C, it's common to provide a function prototype before using the function in the main function or any other functions. A function prototype is a declaration that tells the compiler about the function's name, return type, and parameters. It allows the compiler to check for correctness and helps in resolving any potential conflicts before the actual function call.

Function prototype syntax:

Example using a function prototype:

Remember that function names must be unique, and the function's signature (return type and parameters) must match between the function definition and its call. Additionally, you should always declare or define the function before using it to avoid any compilation errors.