C++ Comments

Comments are added in C++ program for documentation purpose. Comments are explanatory statements that we can in our code to make it easy to understand for anyone reading this source code. We can add comments anywhere and any number of times in our programs. Adding comments in your code is highly recommended and is considered as a good programming practice. Comment are ignored by C++ compilers.

They are meant for human readers, including yourself, your collaborators, or anyone who might work on your code in the future. Comments provide additional information about the code, explaining its purpose, logic, or any other relevant details.

C++ programming language supports two types of comments
  • Single line comments.
  • Multi line comments(inherited from C).

Single Line Comments in C++

  • Single line comment starts with “//” symbol and till end of the line.
  • Everything on the line after // is ignored by compiler.
For Example:
// My first C++ Program
cout << "Hello_World";
cout << "Hello_World"; // My first C++ Program
#include <iostream>

int main() {
    // This is a single-line comment
    std::cout << "Hello, C++!\n"; // This comment is at the end of a line
    return 0;

Multiple Line Comments in C++

  • Multi line comments in C++ start with /* and end with */. Everything between /* and */ is ignored by compiler.
  • Nesting of multi-line comments is not allowed.
  • Inside multi line comment // characters have no special meaning.
For Example:
/* This is my first C++ program
to print Hello World string on screen 
cout << "Hello World";
cout << "Hello World"; /* My first C++ Program */
#include <iostream>

int main() {
    This is a multi-line comment.
    It can span multiple lines.
    std::cout << "C++ Comments Tutorial\n";
    return 0;
Choosing between single-line and multi-line comments often depends on the context and personal preference. Single-line comments are convenient for brief explanations, while multi-line comments are suitable for more extensive commentary.

Why Use Comments?

Comments serve various purposes, contributing significantly to the readability and maintainability of your code. Let's delve into the key reasons why you should use comments in your C++ programs:
  • Code Explanation : Comments provide a platform to explain the logic behind your code. This is crucial for complex algorithms or any non-trivial piece of code. It helps others (and your future self) understand the thought process behind your implementation.
    // Calculate the sum of two numbers
    int sum(int a, int b) {
        return a + b;

  • Documentation : Comments serve as a form of documentation. They describe the purpose of functions, classes, and variables. This becomes invaluable when working on large projects or collaborating with a team.
       Class representing a student.
       Includes details like name, age, and grade.
    class Student {
       // class implementation

  • TODOs and Future Work : Use comments to mark areas where further work is needed or to leave reminders for yourself and others. This is helpful when you identify improvements or optimizations to be made in the future.
    // TODO: Implement error handling
    void processData() {
       // code implementation

  • Debugging Information : Comments can be used to annotate your code with information that aids in debugging. This might include explanations of certain conditions, expected outputs, or anything relevant to the debugging process.
    // Check if the array is sorted
    bool isSorted(int arr[], int size) {
       // debugging note: print array for inspection
       printArray(arr, size);
       // sorting logic

  • License and Copyright Information : Include comments at the beginning of your source files to specify licensing information, copyrights, or any other legal details related to your code. This is particularly important for open-source projects.
       Copyright (c) [Year] [Your Name]
       License: [Type of License]

Best Practices for Writing Comments

While comments are incredibly beneficial, it's equally important to follow best practices to ensure they enhance, rather than hinder, the readability of your code.
  • Be Clear and Concise : Keep your comments clear and to the point. Avoid unnecessary details or verbosity. A concise comment that conveys the essential information is more likely to be read and understood.
    // Increment the counter

  • Update Comments Alongside Code Changes : Whenever you make changes to your code, ensure that you update the corresponding comments. Outdated comments can be misleading and counterproductive.
    // Calculate the square of a number
    int square(int x) {
       // Updated to reflect correct logic
       return x * x; 

  • Avoid Redundant Comments : Don't state the obvious in your comments. If the code is self-explanatory, adding comments like "increment counter" for counter++ is unnecessary.
    // Redundant comment: increment counter

  • Use Proper Grammar and Spelling : Treat your comments with the same care you give to your code. Use proper grammar and spelling to maintain a professional and polished appearance.
    // Misspelled: Caluclate the sum of two numbers
    int calculateSum(int a, int b) {
       return a + b;

  • Be Mindful of Commented-Out Code : While it's common to comment out code for testing or debugging purposes, avoid leaving commented-out code in the final version. It can clutter your codebase and lead to confusion.
    // Commented-out code for testing purposes
    // int result = add(3, 4);


Congratulations! You've now grasped the importance of comments in C++ and how they contribute to writing clean, readable, and maintainable code. As you continue your coding journey, remember that effective commenting is a skill that develops with practice. Embrace the habit of adding meaningful comments to your code, and you'll find yourself not only understanding your code better but also aiding others in navigating your projects.

Comments are your companions in the world of programming—they provide context, explain intentions, and bridge the gap between your code and the minds of those who read it. Happy coding, and may your comments always be clear, concise, and incredibly helpful!