Comments in C++ are non-executable notes written for developers. The compiler ignores them, but they improve readability and document intent.

What Are Comments in C++?

Comments are used to explain code, document algorithms, and leave notes for future maintainers without affecting program execution.

Why Comments Are Important

• Explain complex logic
• Improve readability
• Document function behavior
• Help team collaboration and maintenance

Types of Comments in C++

• Single-line comments
• Multi-line comments

Single-Line Comments

Single-line comments start with // and continue to the end of the line. Use them for short explanations and inline notes.

// This is a single-line comment
int sum = a + b; // add two numbers

When to Use Single-Line Comments

• Clarify a single statement or variable
• Add quick TODOs or reminders
• Explain the purpose of the next line of code

Multi-Line Comments

Multi-line comments start with /* and end with */. They are useful for longer explanations or temporarily disabling blocks of code.

/*
  This is a multi-line comment.
  Use it to explain a function or algorithm.
*/
int factorial(int n) {
  // Base case: factorial of 0 is 1
  if (n == 0) return 1;
  // Recursive case: n * factorial(n-1)
  return n * factorial(n - 1);
}

When to Use Multi-Line Comments

• Document a function or algorithm in detail
• Provide module-level documentation
• Temporarily disable a block of code during debugging

Best Practices for Writing Comments

• Write clear and concise comments
• Explain why, not what — avoid stating the obvious
• Keep comments up to date when code changes
• Use comments to explain intent and design decisions

Common Mistakes to Avoid

• Writing unnecessary comments that clutter code
• Leaving outdated comments that mislead readers
• Explaining obvious code instead of intent
• Writing unclear or vague comments

Benefits of Properly Commented Code

• Improved collaboration
• Easier maintenance
• Faster onboarding for new developers
• Reduced debugging time

Frequently Asked Questions

What are comments in C++?

Comments are non-executable notes that explain and document code for developers.

Do comments affect program execution?

No. The compiler ignores comments, so they do not change program behavior.