Published Aug 26, 2021Updated Mar 27, 2023
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A comment is a piece of text within a program that is not executed. It can be used to provide additional information to aid in understanding the code.

Single-line Comments

Single-line comments are created using two consecutive forward slashes. The compiler ignores any text after // on the same line.

// This line will denote a comment in C

Multi-line Comments

Multi-line comments are created using /* to begin the comment, and */ to end the comment. The compiler ignores any text in between.

This is all commented out.
None of it is going to run!

Header Comment

Multi-line comments can be used to create a header comment at the top of the file. File header comments are used to identify the author of the code, the date the code was written, a description of the program, etc. This is a common convention in the C language.

* FILENAME: hello.c
* DESCRIPTION: This program prints a message to the screen.
* AUTHOR: Gilfoyle
* DATE: 04/20/2023


Here’s a program with a multi-line comment and three single-line comments:

/* Tip Calculator
Written by Sonny */
#include <stdio.h>
int main() {
// Calculate the tip
double total = 18.75;
double tip = total * 0.2;
// Display the tip
printf("The tip is $%.2f\n", tip); // Show two decimal places
return 0;

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