CPP Tutorials

Discovering Comments in C++


In C++, comments play an important role in clarifying and improving the code’s readability. They not only provide explanations about the code but also help in making it easier to understand. Additionally, comments can be used to temporarily disable sections of code during testing or while trying out different alternatives. The primary objective of comments is to offer insights into the purpose and functionality of code lines. Programmers commonly depend on comments to document their programming logic and intentions.

In this article, we will explore the importance of comments, why we need them, and how to use them effectively. So get ready to uncover the secrets of comments and level up your programming skills!

What Exactly Are Comments in C++?

In C++, comments are notes that you add to your code to explain what it’s doing. They don’t affect how the program runs; instead, they help programmers understand the code. Comments are like little reminders or explanations that you write directly in your code.

They are super helpful because they let you explain complex parts of your program in simple words. Comments are ignored by the computer when it’s running the program, so they’re just there to make your code easier for both you and other programmers to read and understand.

How Do We Use Comments in C++?

Using comments in C++ is a simple way to explain your code and make it more understandable. You can add comments by using two forward slashes (//) before the text you want to comment. These comments won’t affect the program’s execution; they’re just there to provide information to programmers who read the code.

You can also create multiline comments by enclosing the text between /* and */. This is useful when you want to comment on a larger section of code or provide more detailed explanations. Remember that comments are essential for others (and even yourself) to comprehend your code in the future, so don’t hesitate to add them whenever necessary!

Comments in C++

Why Comments are used in C++?

Comments in C++ serve various purposes to enhance code quality and understanding. They summarize algorithms, explain variable purposes, and clarify unclear segments. Comments aid in:

  • Easier Debugging: Comments help pinpoint issues by providing context to code sections, making debugging more efficient.
  • Readability: Comments make code readable, offering an overview of its purpose and logic for developers.
  • Skip Execution: Comments can temporarily deactivate code, aiding in testing alternatives or skipping portions.
  • Long-Term Use: After extended periods, comments refresh code memory, enabling quick comprehension during reuse.

Types of Comments in C++

In C++, there are two primary types of comments: single-line comments and multi-line comments.

  1. Single-Line Comments: These comments start with “//” and continue until the end of the line. They are used to explain specific lines of code or provide brief insights.
  2. Multi-Line Comments: These comments are enclosed between “/” and “/”. They can span multiple lines and are useful for explaining larger blocks of code, adding documentation, or temporarily disabling code.

Single-Line Comments

Here’s a C++ code example using single-line comments:

#include <iostream>
using namespace std;

int main() {
    // This is a single-line comment
    cout << "Hello, world!" << endl; // This part will be printed
    // cout << "This won't be printed" << endl;
    return 0;


Hello, world!


  • Text following ‘//‘ in the code is a comment in C++.
  • These comments are not executed as part of the code.
  • They are used to provide explanations or additional information about the code.
  • Comments do not affect the output of the program.

Multi-Line Comments

Here’s a code example of using multi-line comments in C++ with an output:

#include <iostream>
using namespace std;

int main() {
    // This is a single-line comment
    This is a multi-line comment.
    It can span multiple lines.

    cout << "Hello, world!" << endl;

    return 0;


Hello, world!


  • The example includes both single-line and multi-line comments.
  • Single-line comments start with ‘//‘ and only apply to the text following them on the same line.
  • Multi-line comments start with ‘/*‘ and end with ‘*/‘, and can span multiple lines.
  • Comments are used to add explanations or notes to the code.
  • They are not executed as part of the program and are ignored by the compiler.
  • Their main purpose is to improve the readability and understanding of the code for programmers.

Real-life Example of Comments in C++

Imagine you’re working on a team project to create a program that calculates the expenses for a road trip. In your code, you have a section that calculates the total cost of fuel based on the distance traveled and the fuel efficiency of the vehicle. You can use comments to explain how this calculation works, making it easier for your team members (and your future self) to understand the code:

#include <iostream>
using namespace std;

int main() {
    double distance = 500.0;  // distance traveled in miles
    double fuelEfficiency = 25.0;  // miles per gallon

    // Calculate fuel cost
    double fuelCost = (distance / fuelEfficiency) * 3.5;  // Assuming fuel price is $3.50 per gallon

    cout << "Total fuel cost: $" << fuelCost << endl;

    return 0;

In this example, the comments help explain the purpose of each variable and the calculation being performed. This can be incredibly helpful when you or your teammates come back to the code later to understand or modify it.

Problem to Solve

Problem Statement:

You are given a piece of C++ code that calculates the area of a circle. The code is working fine, but it is not well-documented. Your task is to add appropriate comments to the code to make it easier for others to understand.

Here’s the code:

#include <iostream>
#define PI 3.14159
using namespace std;

int main() {
    float radius, area;
    cout << "Enter radius: ";
    cin >> radius;
    area = PI * radius * radius;
    cout << "Area of the circle is: " << area << endl;
    return 0;


  1. Add a multi-line comment at the beginning of the code to describe what the program does.
  2. Use single-line comments to explain the purpose of each line or block of code.
  3. Make sure to explain the use of the #define directive and the PI constant.
  4. Comment on the calculation of the area.
  5. Explain the input and output operations.

Remember, the goal of commenting is to make the code easier to understand for others (and for you when you come back to it later). So, try to make your comments clear and concise.

Pros and Cons of Using Comments

Enhances code readabilityOveruse of comments can make the code cluttered
Provides explanations and contextOutdated or incorrect comments can mislead developers
Facilitates code maintenanceIgnoring code changes may result in misleading comments
Helps in collaboration and understandingExcessive commenting can be time-consuming
Enables easier debugging and troubleshootingComments may become outdated and need to be updated
The Good and the Bad of Using Comments

Key Points to Remember

  • Comments in C++ act as secret messages to yourself and other developers reading your code.
  • They enhance code readability and understanding.
  • Comments can provide explanations and context about the purpose or functionality of code.
  • They help others understand the reasoning behind certain code decisions.
  • Comments are not executed as part of the program and do not affect its functionality.
  • Effective use of comments can make code maintenance and debugging easier.
  • Comments are an important tool for collaboration and documentation in software development.


In summary, comments play a vital role in C++ programming. By mastering the art of using comments effectively, you can enhance the quality of your code. So keep practicing and honing your commenting skills, and before you know it, you’ll become a pro at leveraging the power of comments in your C++ programs!


  • What are the comments in C++?
    Comments in C++ are like secret messages to yourself or to other people who might read your code. They don’t change how the code runs, but they can explain what the code is doing or why it’s doing it.
  • Why do we use comments in C++?
    We use comments in C++ to make our code easier to read and understand. They can help us and others understand why the code was written a certain way.
  • How do we use comments in C++?
    We use comments in C++ by writing // for a single-line comment or /* */ for a multi-line comment, followed by the comment text.
  • Can using comments make code more confusing?
    Yes, if you use too many comments or if your comments are unclear, they can make your code more confusing. It’s important to use comments wisely and to make sure your comments are clear and helpful.
  • What are some examples of using comments in C++?
    Some examples include // This is a single line comment, ` /* This is a multi-line comment */, andint myVar = 5; // This comment explains what this line does. In each of these examples, the comments help us understand what the code is doing.

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