Comments in C++ are annotations in the code that are ignored by the compiler. They are used to improve the readability of the code by providing explanations, clarifications, or notes for anyone reading the code, including the original author. Comments are crucial for documentation, making it easier to understand the logic and functionality of the code later on.

Types of Comments

C++ supports two types of comments:

1. Single-line Comments

   • These comments begin with // and continue until the end of the line.
   • They are useful for short notes or explanations.

   Example:

   int x = 10; // This is a single-line comment
   

2. Multi-line Comments

   • These comments begin with /* and end with */.
   • They can span multiple lines and are useful for longer explanations or when commenting out blocks of code.

   Example:

   /* This is a multi-line comment
      that spans multiple lines. */
   int y = 20;
   

Guidelines for Using Comments

1. Be Clear and Concise: Comments should be straightforward and to the point. Avoid unnecessary jargon or overly complex language.

2. Explain Why, Not What: It's often more helpful to explain why something is done rather than what is being done, especially if the code is not self-explanatory.

3. Update Comments: Always update comments when you change the associated code. Outdated comments can be more confusing than no comments at all.

4. Use Comments Judiciously: Avoid over-commenting, which can clutter the code. Strive for self-documenting code where possible, meaning that the code itself is clear enough to explain its purpose without needing extensive comments.

5. Comment Out Code Temporarily: Use comments to disable portions of code temporarily during testing or debugging.

Examples

Single-line Comments:

#include <iostream>

int main() {
    // Initialize a variable
    int age = 25; // Age of the user
    std::cout << "Hello, World!" << std::endl; // Print greeting
    return 0; // End of program
}

Multi-line Comments:

#include <iostream>

/* This program demonstrates the use of comments in C++.
   It prints a greeting message to the console. */
int main() {
    std::cout << "Hello, World!" << std::endl;
    return 0;
}