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C++ Comments Tutorial | Single-Line and Multi-Line Comments

Learn how to use comments in C++ with examples. Understand single-line and multi-line comments, why comments are important, and how they improve readability in C++ programs.

1. What are Comments?

Comments are notes written inside a program to explain the code.

Comments are ignored by the compiler, so they do not affect the execution of the program.

Why do we use comments?

Comments help us to:

Explain the purpose of code
Make programs easier to understand
Remember what a section of code does
Make code easier to maintain

2. Types of Comments in C++

There are two common types of comments:

Single-line comments
Multi-line comments

3. Single-Line Comments

A single-line comment is used to write a comment on one line.

It starts with:

//

Everything after // on that line is treated as a comment.

Example 1

#include <iostream>
using namespace std;

int main() {
    // This is a single-line comment

    cout << "Hello World";

    return 0;
}

Output

Hello World

The compiler ignores:

// This is a single-line comment

Example 2: Comment After Code

int age = 20;  // Store student's age

Here:

int age = 20; → actual code
// Store student's age → comment

4. Multi-Line Comments

A multi-line comment is used when the comment covers more than one line.

It starts with:

/*

and ends with:

*/

Example

#include <iostream>
using namespace std;

int main() {

    /*
       This program displays
       a simple message
       on the screen.
    */

    cout << "Hello World";

    return 0;
}

Output

Hello World

Everything between:

/*

and:

*/

is ignored by the compiler.

5. Difference Between Single-Line and Multi-Line Comments

Single-Line Comment	Multi-Line Comment
Used for one line	Used for multiple lines
Starts with `//`	Starts with `/*`
Ends at the end of the line	Ends with `*/`
Example: `// My comment`	Example: `/* My comment */`

6. Complete Example

#include <iostream>
using namespace std;

int main() {

    // Declare two numbers
    int a = 10;
    int b = 20;

    /*
       Add the two numbers
       and display the result.
    */
    int sum = a + b;

    cout << sum;

    return 0;
}

Output

⭐ Quick Revision

Single-Line Comment

// This is a comment

Multi-Line Comment

/*
   This is a
   multi-line comment
*/

Remember

Comments are written for programmers, not for the compiler.

They help make C++ programs clear, readable, and easy to understand.