Comments

Part of the Fundamentals section of Coddy's C# journey — lesson 3 of 69.

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
Console.WriteLine("Hello, Coddy!");

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

Console.WriteLine("Hello, Coddy!"); // This prints Hello, Coddy!

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

/* This is a multi-line comment.
   The compiler ignores all of it. */
Console.WriteLine("Welcome!");

Comments can also temporarily disable a line of code without deleting it:

// Console.WriteLine("This line will NOT run");
Console.WriteLine("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

using System;

public class Program {
    public static void Main(string[] args) {
        // Type your code below
        ? Console.WriteLine("Goodbye!");
        Console.WriteLine("Hello, C#!");
    }
}

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

7Basic IO

Basic Output String Interpolation Reading Input Parse Recap - Till 120 Recap - True or False

10Methods (Functions)

Declaring Methods Method Parameters Return Types Optional Parameters Recap - Validation Function Void Methods

13Iterating Over Collections

Using For Loop Foreach Loop Common Array Operations

2Variables Part 1

Numbers Char String Boolean Type Declaration

5Operators Part 2

Comparison Operators Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3

8Calculator App

Welcome Message Getting Numbers

Basic Operations

Formatted Output

11Arrays Basics

Declaring Arrays Accessing Elements Modifying Arrays Array Methods Recap - Product Array Edit Recap - Reversed Array

14Final Challenges

Number Pattern Pattern Finder Student Grade Calculator

3Variables Part 2

Var Constants Naming Conventions Recap - Initialize Variables Type Casting

6Decision Making

If Statement If - Else Switch Statement Ternary Operator Recap - If Else Nested If - Else

9Loops

For Loop While Loop Do While Loop Break Continue Nested Loop Infinite Loop Recap - Dynamic Input

12String Operations

String Methods Part 1 String Methods Part 2 String Formatting