Comments in C++

In C++, comments are used to explain code to readers or to add notes to yourself. These comments are ignored by the compiler and do not affect the program’s functionality. C++ supports two types of comments:

  1. Single-line comments start with two forward slashes (//) and can be used to add comments on a single line.
  2. Multi-line comments start with /* and end with */. They can be used to add comments that span multiple lines.

Comments are a crucial part of programming, as they help other developers understand the code you have written. It is best practice to add comments to your code regularly to ensure that the code remains clear and easy to read. Additionally, comments can be used to document functions and classes, as well as provide instructions on how to use them.


// single-line comment

  documentation comment 

// comment including parameters
	add function
	@param x integer value to add
    @param y integer value to add
	@return addition of this two parameters
int add(int x, int y) {
    return x + y;

Code Example

#include <iostream>  // Include the input-output stream library
using namespace std; // Use the standard namespace

	add function
	@param x integer value to add
    @param y integer value to add
	@return addition of these two parameters
int add(int x, int y) {
    return x + y; // Return the sum of x and y

int main() {
    // Variable declaration and initialization
    double x = 2, y = 4; // Declare and initialize x and y as double

    cout << add(x, y); // Output the result of the add function

    // The backslash is a continuation character and will continue the comment to the following line \
    this is a comment too!

    The return value is the exit code of the program, 
    the shell can read and use it. The 0 exit code means 
    that the program executed successfully 
    return 0; // Return 0 to indicate successful execution

Detailed Code Explanation

  1. #include <iostream>
    • This line includes the standard input-output stream library, which is essential for using std::cout and other input-output functionalities.
  2. using namespace std;
    • This directive allows the program to use all the entities in the std namespace without prefixing them with std::.
  3. int add(int x, int y)
    • Function Definition: Defines a function named add that takes two integer parameters, x and y.
    • return x + y;: Returns the sum of the parameters x and y.
  4. int main()
    • The main function is the entry point of the program where execution begins.
  5. double x = 2, y = 4;
    • Variable Declaration and Initialization: Declares two variables, x and y, of type double and initializes them with values 2 and 4, respectively.
  6. cout << add(x, y);
    • Output Statement: Calls the add function with x and y as arguments and outputs the result using cout.
    • Type Promotion: Here, x and y are double, but they are passed to a function that expects int. The values will be implicitly converted to int (2.0 becomes 2, and 4.0 becomes 4).
  7. Comment with Continuation Character \
    • The backslash (\) is used to extend a comment to the next line, making it part of the same comment.
    • this is a comment too!: This is an extension of the previous line’s comment due to the backslash.
  8. Block Comment /* ... */
    • Multi-line Comment: Explains that the return value of the main function is the exit code of the program.
    • 0 Exit Code: Indicates that the program executed successfully.
  9. return 0;
    • Return Statement: Ends the main function and returns 0 to the operating system, signaling successful execution of the program.

This code demonstrates basic concepts of C++ including function definition, type conversion, variable declaration, comments, and output operations. The use of comments, both single-line and multi-line, helps in explaining various parts of the code for better understanding.