Comments

Learn to write single-line (//) and multi-line (/* */) comments in C.

Comments

Comments are text that explains the code and is ignored by the compiler. C has two kinds of comments:

Single-line: // this is a comment
Multi-line: /* this is also a comment */

Comments make code readable and convey your intent to other developers. Avoid adding misleading explanations.

What are comments for?

Comments serve three main purposes:

Explanation: describe complex logic to the reader
Documentation: say what functions do and what parameters they take
Disabling: temporarily turn off trial code

A good comment explains why, not what. Avoid restating the obvious; well-named code often speaks for itself.

Exercise Write a program with a comment

Write a C program: #include <stdio.h>, int main(void), and print Hello with printf. Also add at least one single-line comment starting with //.

Show example solution

#include <stdio.h>

// Account
int main(void) {
    printf("Hello");
    return 0;
}

Test yourself

Single-line comment marker

____ this is a comment

Show answer

// this is a comment

Multi-line comment syntax?
- /* Comment */
- # Comment
- 
- // Comment
Show answer

/* Comment */ — /* ... */ is a multi-line comment.
Match comment types

//

Single-line
/* */

Multi-line
#

Not a comment
Explanation

Intent

Next lesson: printf and escapes

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