Declare a Function

Part of the Fundamentals section of Coddy's C journey — lesson 46 of 63.

A function in C is a block of code that performs a specific task. Functions help organize code, make it reusable, and improve readability. Here's the basic structure of a function declaration in C:

return_type function_name(parameter1_type parameter1_name, parameter2_type parameter2_name, ...) {
    // code to be executed
    return value; // if the return_type is not void
}

For example, a simple function that greets the user might look like this:

void greet() {
    printf("Hello, welcome to C programming!");
}

To use (call) this function in your main program, you would write:

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

Functions can also take parameters and return values, which we'll explore in later lessons.

Challenge

Easy

Create a function named printNumbers that prints the numbers from 1 to 5. Then, in the main function, call this function twice.

Your output should look like this:

1 2 3 4 5
1 2 3 4 5

Make sure not to include any spacing after the number 5, and also add a new line after the number 5 (\n)

Cheat sheet

A function in C is a block of code that performs a specific task. Functions help organize code, make it reusable, and improve readability.

Basic function structure:

return_type function_name(parameter1_type parameter1_name, parameter2_type parameter2_name, ...) {
    // code to be executed
    return value; // if the return_type is not void
}

Example of a simple function:

void greet() {
    printf("Hello, welcome to C programming!");
}

To call a function:

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

Try it yourself

#include <stdio.h>

// Declare your function here

int main() {
    // Call your function twice here
    
    return 0;
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

C Language Hello World!Comments Basic Program Structure

4Control Flow

If Statement If - Else Else-If Switch Case Ternary Conditional Operator Recap Challenge Nested If - Else

7Functions

Declare a FunctionReturn Types Parameters Recap Challenge #1 Recursion Basics Function Prototypes Recap Challenge #2