C Programming Language Tutorial - GeeksforGeeks

Last Updated : 06 Jan, 2025

C is a general-purpose, procedural, and middle-level programming language used for developing computer software, system programming, applications, games, and more. Known for its simplicity and efficiency, C is an excellent choice for beginners as it provides a strong foundation in programming concepts. C was developed by Dennis M. Ritchie at Bell Laboratories in 1972. Initially, it was created for programming the UNIX operating system.

• Bridges the gap between low-level programming (closer to hardware and machine code) and high-level programming (closer to human-readable code).
• Referred as the "mother of all programming languages" because it influenced many modern programming languages like C++, Java, Python and Go.
• C programs are platform-independent i.e. code can be compiled and run on different systems with minimal modifications.
• Does not require heavy runtime environments or libraries, making it ideal for low-resource systems.

Hello World Program

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

In this C tutorial, we’ll cover everything from basic syntax, data types, and control structures to advanced topics like pointers, memory management, and file handling. By the end, you’ll gain hands-on experience and a solid understanding of C, which is essential for mastering other programming languages like C++ and Java. Let’s dive into the world of C programming and build a strong coding foundation!

C Overview

• What is C Language?
• C Features
• C Standards
• Setting Up C Development Environment
• Hello World Program
• Compiling a C Program: Behind the Scenes

C Basics

• Tokens
• Identifiers
• Keywords
• Comments
• Variables
• Constants
• Data Types
• Data Type Modifiers
• Type Conversion
• Operators

C Input/Output

• Basic Input and Output
• printf
• scanf
• Format Specifiers
• Escape Sequence

C Operators

• Arithmetic Operators
• Unary Operators
• Assignment Operators
• Logical Operators
• Bitwise Operator
• Signed Number Representation
• Operator Precedence and Associativity

C Flow Control

• if Statement
• if…else Statement
• if-else-if Ladder
• Switch Statement
• Using Range in Switch Case
• for Loop
• while looping
• do…while Loop
• continue Statement
• break Statement
• goto Statement

C Functions

• Introduction to Functions
• User-Defined Function
• Parameter Passing Techniques
• Main Function
• Inline Function
• Nested Functions

C Arrays

• Introduction to Arrays
• Length of Array
• Multidimensional Arrays
• Pass Array to Functions
• Pass a 2D Array as a Parameter

C Strings

• Introduction to Strings
• Length of String
• String Comparison
• String Copy
• String Concatenation
• Array of Strings
• String Functions

C Pointers

• Introduction to Pointers
• Pointer Arithmetics
• Pointer to Pointer (Double Pointer)
• Function Pointer
• Declare Function Pointer
• Pointer to an Array
• Constant Pointer
• Pointer vs Array
• Dangling, Void, Null and Wild Pointers
• Near, Far and Huge Pointers
• restrict Keyword

C Dynamic Memory Allocation

• Memory Structure of a Program
• Dynamic Memory Allocation (malloc(), calloc(), and free())
• Memory Leak

C Structures and Union

• Introduction to Structures
• Array of Structures
• Structure Pointer
• Structure Member Alignment
• Introduction to Unions
• Bit Fields
• Structure vs Union
• Anonymous Union and Structure
• Enumeration (or enum)
• dot (.) Operator
• typedef

C Storage Classes

• Introduction to Storage Classes
• extern Keyword
• Static Variables
• Initialization of Static Variables
• Static Functions
• Understanding “volatile” Qualifier
• Understanding the “register” Keyword

C Preprocessor

• Introduction to Preprocessors
• Preprocessor Directives
• How a Preprocessor Works?
• Header Files
• Header Files “stdio.h” vs “stdlib.h”
• Write Your Own Header File
• Macros and its Types
• Interesting Facts About Macros and Preprocessors
• # and ## Operators
• Print a Variable Name
• Multiline Macros
• Variable Length Arguments for Macros
• Branch Prediction Macros in GCC
• typedef versus #define
• Difference Between #define and const

C File Handling

• Basics of File Handling
• fopen() Function
• EOF, getc() and feof()
• fgets() and gets()
• fseek() vs rewind()
• Return Type of getchar(), fgetc() and getc()
• Read/Write Structure From/to a File
• Print Contents of File
• Delete a File
• Merge Contents of Two Files into a Third File
• printf vs sprintf vs fprintf
• getc() vs getchar() vs getch() vs getche()

C Error Handling

• Error Handling
• Using goto for Exception Handling
• Error Handling During File Operations
• Handle Divide By Zero and Multiple Exceptions

C Programs

• Basic C Programs
• Control Flow Programs
• Pattern Printing Programs
• Functions Programs
• Arrays Programs
• Strings Programs
• Conversions Programs
• Pointers Programs
• Structures and Unions Programs
• File I/O Programs
• Date and Time Programs
• More C Programs

Miscellaneous

• Date and Time
• Input-Output System Calls
• Signals
• Program Error Signals
• Socket Programming
• _Generics Keyword
• Multithreading

C Interview Questions

• Top 50 C Programming Interview Questions and Answers
• Commonly Asked C Programming Interview Questions | Set 1
• Commonly Asked C Programming Interview Questions | Set 2
• Commonly Asked C Programming Interview Questions | Set 3

C Compiler

C compiler is a software that translates human-readable C language code into machine code or an intermediate code that can be executed by a computer’s central processing unit (CPU).

There are many C compilers available in the market, such as GNU Compiler Collection (GCC), Microsoft Visual C++ Compiler, Clang, Intel C++ Compiler, and TinyCC (TCC).

For this tutorial, we will be using the GNU-based online C compiler provided by GeeksforGeeks which is developed for beginners and is very easy to use compared to other compiler/IDE’s available on the web.

Features of C Language

There are some key features of C language that show the ability and power of C language:

• Simplicity and Efficiency: The simple syntax and structured approach make the C language easy to learn.
• Fast Speed: C is one of the fastest programming language because C is a static programming language, which is faster than dynamic languages like Javascript and Python. C is also a compiler-based which is the reason for faster code compilation and execution.
• Portable: C provides the feature that you write code once and run it anywhere on any computer. It shows the machine-independent nature of the C language.
• Memory Management: C provides lower level memory management using pointers and functions like realloc(), free(), etc.
• Pointers: C comes with pointers. Through pointers, we can directly access or interact with the memory. We can initialize a pointer as an array, variables, etc.
• Structured Language: C provides the features of structural programming that allows you to code into different parts using functions which can be stored as libraries for reusability.

Applications of C Language

C was used in programs that were used in making operating systems. C was known as a system development language because the code written in C runs as fast as the code written in assembly language.

The use of C is given below:

• Operating Systems
• Language Compilers
• Assemblers
• Text Editors
• Print Spoolers
• Network Drivers
• Modern Programs
• Databases
• Language Interpreters
• Utilities

FAQs

1. How to learn C easily?

The first steps towards learning C or any language are to write a hello world program. It gives the understanding of how to write and execute a code. After this, learn the following:

• Variables
• Operators
• Conditionals
• Loops and Errors
• Arrays and Strings 
• Pointers and Memory
• Functions
• Structures
• Recursions 

2. Difference between C and C++?

 3. Is C easy to learn for beginners?

While C is one of the easy languages, it is still a good first language choice to start with because almost all programming languages are implemented in it. It means that once you learn C language, it’ll be easy to learn more languages like C++, Java, and C#.

4. Why should we learn C first rather than C++?

C is a ‘mother of all languages.’ It provides a solid understanding of fundamental programming concepts and is considered easier to grasp. C offers versatile applications, from software development to game programming, making it an excellent choice for building a strong programming foundation.