Comments in C/C++

Difficulty Level : Basic
Last Updated : 13 Nov, 2019

A well-documented program is a good practice as a programmer. It makes a program more readable and error finding become easier. One important part of good documentation is Comments.

In computer programming, a comment is a programmer-readable explanation or annotation in the source code of a computer program
Comments are statements that are not executed by the compiler and interpreter.

In C/C++ there are two types of comments :

Single line comment
Multi-line comment

Single line Comment

Represented as // double forward slash

It is used to denote a single line comment. It applies comment to a single line only. It is referred to as C++-style comments as it is originally part of C++ programming.
for example:

// single line comment

Example: This example goes same for C and C++ as the style of commenting remains same for both the language.

// C program to illustrate 
// use of multi-line comment 
#include <stdio.h> 
int main(void) 
{ 
  
    // Single line Welcome user comment 
    printf("Welcome to GeeksforGeeks"); 
    return 0; 
} 

Output:

Welcome to GeeksforGeeks

Multi-line comment

Represented as /* any_text */ start with forward slash and asterisk (/*) and end with asterisk and forward slash (*/).
It is used to denote multi-line comment. It can apply comment to more than a single line. It is referred to as C-Style comment as it was introduced in C programming.

/*Comment starts
continues
continues
.
.
.
Comment ends*/

Example: This example goes same for C and C++ as the style of commenting remains same for both the language.

/* C program to illustrate  
use of  
multi-line comment */
#include <stdio.h> 
int main(void) 
{ 
  
    /* Multi-line Welcome user comment  
    written to demonstrate comments 
    in C/C++ */
    printf("Welcome to GeeksforGeeks"); 
    return 0; 
} 

Output:

Welcome to GeeksforGeeks

Comment at End of Code Line

You can also create a comment that displays at the end of a line of code. But generally its a better practice to put code before the line of code.
Example: This example goes same for C and C++ as the style of commenting remains same for both the language.

 int age; // age of the person

When and Why to use Comments in programming?

A person reading a large code will be bemused if comments are not provided about details of the program.
Comments are a way to make a code more readable by providing more description.
Comments can include a description of an algorithm to make code understandable.
Comments can be helpful for one’s own self too if code is to be reused after a long gap.

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