Comments

Part of the Fundamentals section of Coddy's C++ journey — lesson 3 of 74.

Comments are notes you write inside your code. The compiler completely ignores them - they exist only to help humans understand the code.

To write a single-line comment, use //. Everything after // until the end of the line is ignored:

// This is a comment
std::cout << "Hello, World!";

A comment can also be written at the end of a line, after the code:

std::cout << "Hello, World!"; // This prints Hello, World!

For comments that span several lines, use /* to start and */ to end:

/* This is a multi-line comment.
   The compiler ignores all of it. */
std::cout << "Welcome!";

Comments can also temporarily disable a line of code without deleting it. This is called commenting out:

// std::cout << "This line will NOT run";
std::cout << "This line will run";

Note: Every multi-line comment that starts with /* must be closed with */, otherwise the compiler treats everything after it as a comment.

Challenge

Beginner

Fix the code so that only Hello, C++! is printed.

Replace the ? with the symbols that turn a line into a comment
The line printing Goodbye! should become a comment so it does NOT run
Only change the line that starts with ?

Try it yourself

#include <iostream>

int main() {
    // Type your code below
    ? std::cout << "Goodbye!" << std::endl;
    std::cout << "Hello, C++!" << std::endl;

    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++Hello World!CommentsBasic Program Structure

4Operators Part 1

Arithmetic Operators Modulo Operator Increment/Decrement Post Increment/Decrement Arithmetic Shortcuts Comparison Operators String Comparison

7Input/Output Basics

cout Statement cin Statement String Input Recap - Till 120 Recap - True or False

10Functions

Declare a Function Parameters Return Types Function Overloading Recap - Sigma Function Recap - Validation Function Void Functions

13Final Challenges

Number Pattern Pattern Finder Student Grade Calculator