Learn C Programming

C is a powerful general-purpose programming language. It is fast, portable and available in all platforms.

If you are new to programming, C is a good choice to start your programming journey.

This is a comprehensive guide on how to get started in C programming language, why you should learn it and how you can learn it.

TABLE OF CONTENTS

• C Tutorials
• What is C Programming?
• Reasons to Learn C
• Your First C Program
• Recommended Books
• Things to Remember

IN A HURRY? HERE ARE QUICK LINKS TO OUR TUTORIALS AND Examples.

INTRODUCTION

• Keywords & Identifier
• Variables & Constants
• C Data Types
• C Input/Output
• C Operators
• Basic Examples

FLOW CONTROL

• if...else Statement
• C for Loop
• C while Loop
• break and continue
• switch Statement
• Decision Examples

FUNCTIONS

• Functions Introduction
• User-defined Function
• Function Types
• Recursion in C
• Variable Scope
• Function Examples

ARRAYS

• C Arrays Introduction
• Multidimensional Array
• Arrays & Functions
• Strings in C
• String Functions
• Array Examples

C POINTERS

• C Pointers
• Pointers & Arrays
• Pointers & Functions
• Memory Management
• Pointer Examples

STRUCTURE & FILE

• C Structure
• Structure & Pointers
• Structure & Functions
• C Unions
• Structure Examples
• Files Handling

ADDITIONAL RESOURCES

• C Examples
• C Library Function

What is C (Programming Language)? - The Basics

Before getting started with C programming, lets get familiarized with the language first.

C is a general-purpose programming language used for wide range of applications from Operating systems like Windows and iOS to software that is used for creating 3D movies.

C programming is highly efficient. That’s the main reason why it’s very popular despite being more than 40 years old.

Standard C programs are portable. The source code written in one system works in another operating system without any change.

As mentioned, it’s a good language to start learning programming. If you know C programming, you will not just understand how your program works, but will also be able to create a mental picture on how a computer works.

More information on C Language.

History of C programming

Features of C Programming Language

Should you learn C programming?

If only it were possible to answer this question with a simple “yes” or “no”. Unfortunately, it’s not an easy question to answer and varies from person to person.

Personally speaking, I love C programming. It is a good language to start your programming journey if you are a newbie. Even if you are an experienced programmer, I recommend you to learn it at some point; it will certainly help.

What will you gain if you learn C?

If you don’t know C, you don’t know what you are doing as a programmer. Sure, your application works fine and all. But, if you can’t say why while (*s++ = *p++); copies a string, you’re programming on a superstition. ( Joel Spolsky’s words, not mine ).

1. You will understand how a computer works.
   
   If you know C, you will not only know how your program works but, you will be able to create a mental model on how a computer works (including memory management and allocation). You will learn to appreciate the freedom that C provides unlike Python and Java.
   
   Understanding C allows you to write programs that you never thought were possible before (or at the very least, you will have a broader understanding of computer architecture and programming as a whole).
2. C is the lingua franca of programming.
   
   Almost all high-level programming languages like Java, Python, JavaScript etc. can interface with C programming. Also, it’s a good language to express common ideas in programming. Doesn’t matter if the person you are talking with doesn’t know C, you can still convey your idea in a way they can understand.
3. Opportunity to work on open source projects that impact millions of people.
   
   At first, you may overlook the fact that C is an important language. If you need to develop a mobile app, you need Java (for Android), Swift and Objective C (for iOS). And there are dozens of languages like C#, PHP, ASP.net, Ruby, Python for building web application. Then, where is C programming?
   
   Python is used for making wide range for applications. And, C is used for making Python. If you want to contribute to Python, you need to know C programming to work on Python interpreter that impacts millions of Python programmers. This is just one example. A large number of softwares that you use today is powered by C.
   
   Some of the larger open source projects where C programming is used are Linux Kernel, Python Interpreter, SQLite Database.
   
   Another language that’s commonly used for large open source project is C++. If you know C and C++, you can contribute to large open source projects that impacts hundreds of millions of people.
4. You will write better programs.
   
   To be honest, this statement may not be true all the time. However, knowing how computer works and manage memory gives you insight on how to write efficient code in other programming languages.
5. You will find it much easier to learn other programming languages.
   
   A lot of popular programming languages are based on C (and C++, considered superset of C programming with OOP features). If you know C, you will get a head start learning C++.
   
   Languages like C# and Java are related to C and C++. Also, the syntax of JavaScript and PHP is similar to C.
   
   If you know C and C++ programming, you will not have any problem switching to another language.

Reasons not to learn C programming

You can create awesome softwares without knowing C programming at all. Jeff Atwood, one of the creators of Stackoverflow.com, apparently doesn’t know C and Stack Overflow is a really good web application.

If you are busy and don’t want to invest time on something that doesn’t have direct effect on your day-to-day work, C programming is not for you.

Also, if you are a newbie and want to start learning programming with an easier language (C is not the easiest of language to learn), you can start with Python.

Verdict on whether to learn C programming or not

For newbie:

For many, C programming is the best language to start learning programming. However, if you want to start with an easier language which is clean and easier to grasp, go for Python.

For experienced programmers:

It’s not absolutely essential but there are perks of learning C programming.

Don’t leave your current project immediately (I know you won’t) to learn C. You can learn it when you have free time and want to expand your programming skills.

I believe, it’s not necessary to learn C immediately. However, you should learn C eventually.

Compile and run C programming on your OS

There are numerous compilers and text editors you can use to run C programming. These compilers and text editors may differ from system to system.

You will find the easiest way to run C programming on your computer (Windows, Mac OS X or Linux) in this section.

Run C program Online

Run C Programming in Mac OS X

Run C programming on Linux

Run C Programming in Windows (XP, 7, 8 and 10)

To run C Programming in Windows, download a software called Code::Blocks. Then, write C code, save the file with .c extension and execute the code.

To make this procedure even easier, follow this step by step guide.

1. Go to the binary release download page of Code:Blocks official site.
2. Under Windows XP / Vista / 7 / 8.x / 10 section, click the link with mingw-setup (highlighted row) either from Sourceforge.net or FossHub.
   
3. Open the Code::Blocks Setup file and follow the instructions (Next > I agree > Next > Install); you don’t need to change anything. This installs the Code::Blocks with gnu gcc compiler, which is the best compiler to start with for beginners.
4. Now, open Code::Blocks and go to File > New > Empty file (Shortcut: Ctrl + Shift + N)
   
5. Write the C code and save the file with .c extension. To save the file, go to File > Save (Shortcut: Ctrl + S).
   Important: The filename should end with a .c extension, like: hello.c, your-program-name.c
   
6. To run the program, go to Build > Build and Run (Shortcut: F9). This will build the executable file and run it.

If your program doesn’t run and if you see error message "can't find compiler executable in your search path(GNU GCC compiler)", go to Settings > Compiler > Toolchain executables and click Auto-detect. This should solve the issue in most cases.

The fun begins: Your first C program

You will learn to write a “Hello, World!” program in this section.

Why “Hello, World!” program?

“Hello, World!” is a simple program that displays “Hello, World!” on the screen. Since, it’s a very simple program, it is used to illustrate the basic syntax of any programming language.

This program is often used to introduce programming language to a beginner. So, let’s get started.

#include <stdio.h>
int main()
{
    printf("Hello, World!\n");
    return 0;
}

How “Hello, World!” program works?

Include stdio.h header file in your program.

C programming is small and cannot do much by itself. You need to use libraries that are necessary to run the program. The stdio.h is a header file and C compiler knows the location of that file. To use the file, you need to include it in your program using #include preprocessor.

Why do you need stdio.h file in this program?

In this program, we have used printf()function which displays the text inside the quotation mark. Since printf() is defined in stdio.h, you need to include stdio.h.

The main() function

In C programming, the code execution begins from the start of main() function (doesn’t matter if main() isn’t located at the beginning).

The code inside the curly braces { } is the body of main() function. The main() function is mandatory in every C program.

int main() {
}

This program doesn’t do anything but, it’s a valid C program.

The printf() function

The printf() is a library function that sends formatted output to the screen (displays the string inside the quotation mark). Notice the semicolon at the end of the statement.

In our program, it displays Hello, World! on the screen.

Remember, you need to include stdio.h file in your program for this to work.

The return statement

The return statement return 0; inside the main() function ends the program. This statement isn’t mandatory. However, it’s considered good programming practice to use it.

Key notes to take away

• All C program starts from the main() function and it’s mandatory.
• You can use the required header file that’s necessary in the program. For example: To use sqrt() function to calculate square root and pow() function to find power of a number, you need to include math.h header file in your program.
• C is case-sensitive; the use of uppercase letter and lowercase letter have different meanings.
• The C program ends when the program encounters the return statement inside the main()function. However, return statement inside the main function is not mandatory.
• The statement in a C program ends with a semicolon.

Teach Yourself to Code in C

Learn C from Programiz

Programiz offers dozens of tutorials and examples to help you learn C programming from scratch.

The tutorials are designed for beginners who do not have any prior knowledge of C programming (or, any other programming languages). Each tutorial is written in depth with examples and detailed explanation.

Recommended Books in C Programming

If you are serious about learning programming (any programming language including C), you should get yourself a good book. 

Granted, reading a 600 page long programming book takes a lot of time and patience. But, you will get the big picture of programming concepts in the book which you may not find elsewhere.

Here are 3 books we personally recommend.

The C Programming Language (2nd Edition)

This book provides the complete guide to ANSI standard C language.

Most importantly, it’s co-written by Dennis M. Ritchie, creator of C programming language.

Get this book

C Programming: A Modern Approach (2nd Edition)

Personally I believe, this is the best book for beginners.

This book is clear and comprehensive. Also, the Q&A section at the end of each chapter makes this book a must have for beginners. 

Get this book

C Pocket Reference (1st Edition)

Don’t want to search pages and pages to look for a small information? Get this book.

As suggested by the name, it’s a small book for reference.

Get this book

Learn C programming, the right way

Fact: You cannot learn C programming in a day. You might have difficulty grasping the important concepts if you try to learn C programming faster.  

If you just learn the syntax and dive in, your C code may work but you’ll not end up learning C programming the right way.,  

Don’t just look at the example code, run it in your system

Programiz has dozens of examples that will help you understand C programming. However, if you are reading it like a novel without running it in your system, you are doing it wrong.

If you want to learn a new feature of C programming, try to write code related to that feature. If you can’t, copy code from Programiz and run it in your system. Then, try to understand it. Once you understand it, modify the code, make it different and run it again.

Learn to use a Debugging tool

A debugging tool or debugger is a software (that’s already available in IDE) which allows programmers to stop a program at any point and helps to detect and correct errors.

When you have bugs in your program, rather than scratching your head to find the bug, you can use debugger to stop program at any point and find the value of variables to detect the bug. 

Knowing how to use a debugger is an important skill that every programmer should learn. 

Learn the feature the way it is intended 

Imagine a situation: It’s possible to solve a problem with an array. Also, you can solve the same problem with a structure. Technically both are correct, which method will you use?

To answer this question, you should have a good knowledge of when to use an array and when to use a structure.

Suppose, you are switching to C from a different language, let’s say C#. You do not want to write C# style code with C syntax in your C program.

Join C communities

Once you get the hang of writing simple C programs, join online communities and forums. You can help other programmers where you can and ask for help when you are stuck. 

Always follow good programming practice     

Good programming practice are the informal rules which can improve quality and decrease development time of the software.

Some of the programming practices mentioned here are valid in all programming languages whereas some are valid only for C programming. 

Be consistent with the formatting. 

The number of spaces you use in the program doesn’t matter in C. However, that doesn’t mean you should use different number of spaces at different places. Also, use proper indentation so that the code is easier to understand. 

Use one statement per line.

What’s wrong with the following code?

int count; float squareRoot = 10.0; printf(“Square root = %f”, squareRoot);

Actually, the code is perfectly valid. But, wouldn’t this be better:

int count;
float squareRoot = 10.0;
printf(“Square root = %f”, squareRoot);

The goal here is to write code that your fellow programmers can understand.

Naming convention and Consistency!

Give a proper name to variables and functions and be consistent with it. 

int a, b;

Here, a and b are two variables and I have no idea what they do. Instead you can choose name like:

int counter, power; 

Also, follow a convention while naming. For example:

int base_number, powerNumber;

Both conventions: using _ to separate words and using capital letter after first word is popular. However, don’t use both in one program; choose one and be consistent with it.

Start Habit of Using Comments

Comments are part of code that compiler ignores.

You can use comments in your program to explain what you are trying to achieve in your program. This helps your fellow programmer to understand the code.

You can use comments in C programming by using //. For example:

// My first C program

#include <stdio.h>
int main()
{
    printf("Hello, World!\n");   // displays Hello, World! on the screen
    return 0;
}

“Commenting your code is like cleaning your bathroom - you never want to do it, but it really does create a more pleasant experience for you and your guests.”

— Ryan Campbell

We at Programiz think C is a terrific language to learn.

If you are a beginner, it’s a good language to start learning programming. And, if you are a professional programmer with a tight schedule, learn it at your leisure; it will certainly help your brush up on programming basics.