Comments In C - Types, Important Rules, Uses & Examples Explained (2025)

The very first thing a programming instructor would tell one when learning programming is: write clean code that others can understand. This is where comments in C come into the picture. Comments are straightforward textual notes you may add in your program but are ignored by the compiler during execution. They are not instructions for the machine, only for humans reading your code later.

Think about comments in C like sticky notes in your code. They do not affect the actual logic but help developers, students, and even your future self understand why a certain line exists. Programs look like endless puzzles without comments. They are step-by-step instructions that are easy to follow when they have them.

We will cover all aspects of comments in C programming in this guide, learn what are comments in C programming, study the different types of comments in C with examples, learn about the purpose of comments in C programs, and teach about the difference between single-line and multi-line comments in C. By the end of this session, you will not only know how to write comments in C language, but also understand the importance of using comments in C programming for real world projects.

Table of Contents

What are Comments in C Programming?

In any case, comments in C are part of the source code that are made invisible to the compiler. Within comments, you can place normal English sentences, notes or even logical explanations. The whole point behind it is to make the code human-friendly.

For instance:

#include <stdio.h>

int main() {

// This is a single-line comment

printf(“Hello World“); // Printing message

return 0;

}

As it is, the compiler executes only the printf and return. Therefore, the lines beginning with // are comments. They are for humans only.

The easiest answer to what comments in C programming are is: they are meant for readability, not execution.

Purpose of comments in C programs

Every programmer has faced this: you revisit code you wrote months ago, and suddenly it feels alien. Such is the purpose of commenting in C programs.

Explain logic: Other than confusing code, comments will guide you through its easier understanding.

Document assumptions: There are reasons as to why you do what you do.

Debugging help: Lines are temporarily blocked by adding comments.

Collaboration: Comments would be like notes in between developers in a team project.

Ultimately, the goal of comments in C programs is to convert the coding process into human-to-human communication.

Categories of Comments in C with Examples

There are only two categories of comments in C with examples that every programmer must master:

C single-line comments

Single-line comments must begin with //. Everything that follows those slashes in that line is ignored.

Example:

#include <stdio.h>

int main() {

// Initialize variable

int num = 5;

printf(“%d”, num); // Displaying the number

return 0;

}

Multi-Line Comments in C

Multi-line comments start with /* and end with */. They are best used when you want to provide a long explanation that would take up several lines.

Example:

#include <stdio.h>

int main() {

/* This is a multi-line comment

This will say the code in detail

The compiler will skip these lines*/

printf(“Learning comments in C”);

return 0;

}

These two types of comments C with examples take great care of almost all situations when you need documentation inside your code.

Difference Between Single Line Comments and Multi-Line Comments in C

A difference between single-lines and multi-lines comments in C would guide your choice.

Single-line comments: Shorter, faster notes, usually for just one line of code.

Multi-line comments: Longer descriptions, usually kept in top of a block of code.

Flexibility: Multi-lines can be used to comment out sections of code temporarily.

Clarity: Inline single declares are better. Multi-line comments provide a deeper explanation of logic.

Example of disabling code:

/* printf(“This code is skipped”);

printf(“Compiler ignores it”); */

This is how the difference between single-line and multi-line comments in C gives developers flexibility based on context.

How to Write Comments in C Language

Learning how to write comments in C language is as simple as remembering two symbols: // and /*…*/. But writing useful comments is an art.

Hints:

Start off with a short description of the function or logic.
Avoid stating the obvious, such as // increment by 1 next to i++.
Place above complex code blocks, not after every line.
Update when code changes.

So, the answer to how to write comments is – use properly, keep it relevant, and write for humans, not machines.

Benefits of comments in C programming

But why? The benefits of comments in C programming are numerous:

Readability: Makes beginner reader friendly.

Maintainability: Future edits become easier.

Team collaboration: Understanding one logic from different people.

Debugging aid: Code can be toggled quickly by commenting/uncommenting.

In short, benefits from comments come beyond exams or assignments;

it shapes a professional coder from the habits it builds.

Best Practices for Writing Comments in C

Most importantly, follow these golden rules to reap the maximum benefits from comments programming:

Clear, not verbose: Notes should be sharp, not essays.

Keep it up to date: Old comments are worse than none.

Explain intent, not syntax: Don’t comment on every loop with reasons.

Use consistent style: Stick to your pattern single line or multi-line.

Master these best practices to ensure that your comments count and not create clutter.

The Real-World Uses of Comments Programs

Educational projects: Teachers pass assignments by clarity, and comments help score well.

Open-source projects: Without comment, open-source code is unreadable to contributors.

Professional codebases: Companies demand well-commented code for the sake of maintainability.

So, the biggest answer to the question of what comments do in C programs is the world of professional people.

Code Examples with Comments

Example 1: Basic Calculator Program

#include <stdio.h>

int main() {

int a = 10, b = 5;

// Addition

printf(“Sum: %d\n”, a + b);

– Subtraction

printf(“Difference: %d\n”, a – b);

/* Multiplication

Demonstrating multi-line comment */

printf(“Product: %d\n”, a * b);

return 0;

}

Example 2: Loop with Comments

#include <stdio.h>

int main() {

// Print numbers from 1 to 5

for(int i=1; i<=5; i++)

{

printf(“%d “, i); // Inline comment

}

return 0;

}

These kinds of comments with examples are used in day-to-day normal programs.

Also Read:

Develop Your Skills to Code with PW Skills DSA C++ Course

If you want to move beyond just writing comments, and learn how problem solving is done, try the PW Skills DSA C++ Course. With hands-on coding exercises, expert mentors, and real-world examples, you will build the foundation every top programmer needs. Be it students or working professionals, this course is going to sharpen your logic, speed, and confidence in coding. Enroll today and start your way towards programming the smart way!

Why Understanding Comments in C is Important?

The comments may seem small, but they are actually very powerful programming tools. Comments assist in explaining, documenting, debugging, and communicating through a written code. Whether you are a novice writing a first program or a professional managing large complex projects, using various types of comments with examples how to comment program texts will transform you into a thoughtful programmer.

Using comments programming is worth saving all years in time, effort, and the work itself. Next time you code and source this little nugget, remember: your program is for the human that will read it, not just for the compiler.