C++ Comments

In the previous tutorial you learned how to write your first C++ program. Now, let's learn about C++ comments.

Comments are hints that we add to our code, making it easier to read and understand.

Comments are completely ignored by C++ compilers.

For example,

#include <iostream>
using namespace std;

int main() {
    // print Hello World to the screen
    cout << "Hello World";

    return 0;
}

Output

Hello World

Here, // print Hello World to the screen is a comment in C++ programming. The C++ compiler ignores everything after the // symbol.

Note: You can ignore the programming concepts and simply focus on the comments. We will revisit these concepts in later tutorials.

Single Line Comments

In C++, a single line comment starts with // symbol. For example,

// declaring a variable
int a;

// initializing the variable 'a' with the value 2
a = 2;

Here, we have used two single-line comments:

• // declaring a variable
• // initializing the variable 'a' with the value 2

We can also use single line comment like this:

int a;    // declaring a variable

Here, code before // are executed and code after // are ignored by the compiler.

Pro Tip: Remember the shortcut for using comments; it can be really helpful. For most code editors, it's Ctrl + / for Windows and Cmd + / for Mac.

Multi-line comments

In C++, any line between /* and */ is also a comment. For example,

/* declaring a variable
to store salary to employees
*/
int salary = 2000;

This syntax can be used to write both single-line and multi-line comments.

Using Comments for Debugging

Comments can also be used to disable code to prevent it from being executed. For example,

#include <iostream>
using namespace std;
int main() {
   cout << "some code";
   cout << ''error code;
   cout << "some other code";

   return 0;
}

If we get an error while running the program, instead of removing the error-prone code, we can use comments to disable it from being executed; this can be a valuable debugging tool.

#include <iostream>
using namespace std;
int main() {
   cout << "some code";
   // cout << ''error code;
   cout << "some other code";

   return 0;
}

Why use Comments?

We should use comments for the following reasons:

• Comments make our code readable for future reference.
• Comments are used for debugging purposes.
• We can use comments for code collaboration as it helps peer developers to understand our code.

Next, we will learn about C++ variables, constants and literals.