C++ Comments: A Guide to Commenting in C++


When it comes to writing clean and readable code, commenting plays a crucial role. Comments in C++ are essential for providing explanations, adding clarity, and making code more maintainable. In this article, we will explore the various aspects of C++ comments, including their types, usage, and best practices. Whether you are a beginner or an experienced developer, understanding how to effectively use comments in C++ is a valuable skill that can enhance your coding experience.

1. What are Comments in C++?

In C++, comments are annotations that are ignored by the compiler. They are used to add explanatory notes and remarks within the source code. Comments provide information about the code’s purpose, logic, and functionality. They are not executed as part of the program and serve only as a reference for developers.

2. Single-Line Comments

Single-line comments are used to write comments on a single line. In C++, a single-line comment starts with two forward slashes (//). Anything written after the // symbol on the same line is considered a comment and is ignored by the compiler.

// This is a single-line comment in C++
int age = 25; // variable to store age

Single-line comments are ideal for adding short explanations or clarifications next to code statements. They are easy to read and understand.

3. Multi-Line Comments

Multi-line comments, also known as block comments, allow you to write comments spanning multiple lines. In C++, multi-line comments start with /* and end with */. Everything between these delimiters is treated as a comment and is not executed.

/* This is a multi-line comment
   It can span across multiple lines
   This is useful for longer explanations or commenting out blocks of code */
int sum = a + b;

Multi-line comments are helpful when you need to provide detailed explanations, document large sections of code, or temporarily disable a block of code.

4. Commenting Out Code

Commenting out code involves temporarily disabling a portion of the code without deleting it. This practice is useful for debugging or experimenting with different code implementations. By commenting out code, you can isolate specific sections and prevent them from being executed.

To comment out a single line, you can use a single-line comment (//).

// int age = 25; // This line is commented out

To comment out multiple lines, you can enclose the code within multi-line comment delimiters (/* */).

/* int a = 10;
   int b = 20;
   int sum = a + b;
   This code is commented out */

Remember to uncomment the code before deploying it to production or sharing it with others.

5. Best Practices for Commenting

To make your comments more effective, follow these best practices:

Be Clear and Concise

Write comments that are easy to understand and convey the intended message concisely. Use simple and straightforward language to ensure clarity.

Comment the Why, Not the How

Focus on explaining the purpose, logic, or reasoning behind the code rather than describing what the code does. The code should be self-explanatory,

making it unnecessary to comment on every line of code. Instead, provide insights into the design choices, algorithms used, or any assumptions made.

Use Descriptive Variable and Function Names

Well-named variables and functions reduce the need for excessive comments. Choose meaningful names that reflect their purpose and functionality, making the code more self-explanatory.

Update Comments with Code Changes

As you modify your code, remember to update the comments accordingly. Outdated or misleading comments can create confusion and make the code harder to maintain.

Avoid Redundant Comments

Avoid restating the obvious in your comments. Focus on adding value and providing information that is not evident from the code itself.

Comment Important or Complex Sections

Pay extra attention to commenting complex or critical sections of code. If you encounter intricate algorithms, non-obvious optimizations, or workaround solutions, explain them clearly to aid future developers who may work on the codebase.

Be Consistent with Formatting

Maintain a consistent style for your comments throughout the codebase. Use the same commenting conventions and formatting to ensure readability and uniformity.


In conclusion, comments are a vital part of writing clean and maintainable code in C++. They help developers understand the code’s purpose, enhance collaboration, and facilitate debugging and maintenance. By following best practices for commenting, you can create code that is easier to comprehend, modify, and share.

Remember to use comments sparingly, focusing on adding value and providing context where necessary. With well-placed comments, you can make your code more accessible and improve its overall quality.

Frequently Asked Questions (FAQs)

Q: How do you comment out multiple lines in C++?

To comment out multiple lines in C++, you can enclose the code within multi-line comment delimiters (/* */). Everything between these delimiters will be treated as a comment and will not be executed.

Q: What is the difference between comment and / / in C++?

The // syntax is used for single-line comments, whereas /* */ delimiters are used for multi-line comments. Single-line comments are limited to a single line, while multi-line comments can span across multiple lines.

Q: What is a variable and comment in C++?

In C++, a variable is a named memory location used to store data. It allows you to manipulate and process values within a program. On the other hand, a comment is an annotation within the code that provides explanations, remarks, or documentation about the code’s purpose, functionality, or design.

Q: What are the two types of comments?

In C++, there are two types of comments:
Single-line comments: These comments start with // and extend until the end of the line.
Multi-line comments: These comments begin with /* and end with */ and can span across multiple lines.

Q: How can I add comments to my C++ code?

To add comments in your C++ code, you can use the // syntax for single-line comments or enclose the comments within /* */ delimiters for multi-line comments. Simply place your comments adjacent to the relevant code to provide explanations or documentation.

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