Comments in C++

Comments in C++ are used to document code and make it more readable. Comments are ignored by the compiler, but they are very important for human readers.

There are two types of comments in C++:

  1. Single-line comments: Single-line comments start with two forward slashes (//) and end at the end of the line.
  2. Multi-line comments: Multi-line comments start with a slash and an asterisk (/*) and end with an asterisk and a slash (*/).

Single-Line Comments

Single-line comments are indicated by double slashes (//). They are used for comments that span a single line.

// This is a single-line comment int age = 30; // Comment can also appear after code

Multi-Line Comments

Multi-line comments are enclosed within /* and */ and can span multiple lines. They are typically used for longer comments or explanations.

/* This is a multi-line comment spanning multiple lines. */ int number = 42;

Comments can be used to:

  1. Explain what the code does.
  2. Document the code's purpose and assumptions.
  3. Identify the author and date of the code.
  4. Disable code that is not currently needed.
// This function calculates the factorial of a number. int factorial(int n) { // Check if the input number is valid. if (n < 0) { // Throw an exception if the input number is invalid. throw std::invalid_argument("n must be a non-negative integer."); } // Initialize the factorial. int factorial = 1; // Calculate the factorial. for (int i = 1; i <= n; i++) { factorial *= i; } // Return the factorial. return factorial; } // This code is disabled because it is not currently needed. /* int main() { // Calculate the factorial of 5. int factorial = factorial(5); // Print the factorial to the console. std::cout << factorial << std::endl; return 0; } */

It is a good practice to comment your code liberally. This will make your code more readable and easier to maintain for yourself and others.


Comments serve the purpose of documenting code, making it more readable, and explaining the logic or purpose of certain code segments. While comments are essential for understanding and maintaining code, they do not affect the program's functionality and are entirely ignored by the C++ compiler during the compilation process.