Module 1: Introduction to C Programming

Learning Objectives

By the end of this module, you will be able to:

• Understand what programming is.
• Learn the basics of the C programming language.
• Know the history of C.
• Explore the features and applications of C.
• Install the GCC compiler.
• Write and run your first C program.
• Understand how C code is compiled.
• Use comments effectively.
• Build simple beginner projects.

What is Programming?

Programming is the process of writing instructions that tell a computer what to do. These instructions are called programs, and they are written using programming languages.

Think of programming like writing a recipe for a chef. The chef follows each step to prepare a dish. Similarly, a computer follows programming instructions to perform tasks.

Example

Suppose you want a computer to add two numbers.

Algorithm:

1. Read first number.
2. Read second number.
3. Add both numbers.
4. Display the result.

Programming converts this algorithm into code.

Why Learn Programming?

Programming allows you to build:

• Websites
• Mobile Applications
• Desktop Software
• Games
• Operating Systems
• Artificial Intelligence Applications
• Embedded Systems
• Robotics Software

What is C?

C is a general-purpose, procedural programming language developed to create efficient and high-performance software.

It is considered the mother of many modern programming languages because languages such as C++, Java, C#, Objective-C, and many others were influenced by C.

C provides direct access to memory and hardware, making it ideal for system programming.

Why is C Still Popular?

• Very fast execution
• Easy to learn syntax
• Small runtime
• Portable across platforms
• Used in operating systems
• Excellent for learning programming fundamentals

History of C

The C programming language has a rich history.

Timeline

1967

Martin Richards created the BCPL language.

↓

1970

Ken Thompson developed the B language.

↓

1972

Dennis Ritchie developed C at Bell Laboratories.

↓

1978

The famous book The C Programming Language by Brian Kernighan and Dennis Ritchie (often called K&R C) was published.

↓

1989

ANSI standardized C as ANSI C (C89).

↓

Later Standards

• C90
• C99
• C11
• C17
• C23

Today, modern compilers support these standards while remaining compatible with older C code.

Features of C

C has many features that make it one of the most influential programming languages.

1. Simple

C has a small set of keywords and a straightforward syntax.

cCopy
1int age = 20;

2. Fast

Programs written in C execute very quickly because they are compiled directly into machine code.

3. Portable

A C program written on Windows can usually be compiled on Linux or macOS with little or no modification.

4. Structured Programming

Large programs can be divided into smaller functions.

cCopy
1void displayMessage()
2{
3    printf("Welcome!");
4}

5. Rich Library

C provides many standard library functions.

Example:

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1printf();
2scanf();
3strlen();
4sqrt();

6. Efficient Memory Management

Programmers can directly allocate and free memory.

cCopy
1malloc()
2free()

7. Middle-Level Language

C combines the features of both:

• High-level programming
• Low-level programming

This makes it suitable for system software.

8. Extensible

Programmers can create their own functions and libraries.

Applications of C

C is used in many industries.

Operating Systems

Examples:

• Linux
• UNIX
• Windows Kernel (parts)

Embedded Systems

Examples:

• Washing Machines
• Smart TVs
• Routers
• IoT Devices

Database Systems

Examples:

• MySQL
• PostgreSQL (core components)

Compilers

Many compilers are written in C.

Game Engines

Performance-critical game engine components often use C.

Device Drivers

Hardware drivers commonly use C for direct hardware interaction.

Networking Software

Examples:

• Network tools
• Protocol implementations
• Packet analyzers

Scientific Computing

High-performance scientific software often uses C.

Installing GCC Compiler

GCC (GNU Compiler Collection) is one of the most widely used compilers for C.

Windows

Option 1: MinGW-w64

1. Download MinGW-w64.
2. Install the compiler.
3. Add the bin directory to the system PATH.
4. Open Command Prompt.
5. Verify the installation:

bashCopy
1gcc --version

Option 2: MSYS2

Install MSYS2 and use its package manager to install GCC.

Linux (Ubuntu/Debian)

Update package information and install GCC:

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1sudo apt update
2sudo apt install build-essential

Check the version:

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1gcc --version

Fedora

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1sudo dnf install gcc

Arch Linux

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1sudo pacman -S gcc

macOS

Install Apple's Command Line Tools:

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1xcode-select --install

Or install GCC using Homebrew:

bashCopy
1brew install gcc

Writing Your First C Program

Create a file named:

hello.c

Write the following code:

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1#include <stdio.h>
2
3int main()
4{
5    printf("Hello, World!\n");
6    return 0;
7}

Explanation

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1#include <stdio.h>

Includes the Standard Input/Output library, allowing the use of functions like printf().

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1int main()

The main() function is the entry point of every C program.

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1printf("Hello, World!\n");

Prints text to the screen.

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1return 0;

Returns a value to the operating system indicating successful execution.

Compiling and Running the Program

Open a terminal in the folder containing hello.c.

Compile the program:

bashCopy
1gcc hello.c -o hello

Explanation

• gcc → Compiler
• hello.c → Source file
• -o hello → Output executable named hello

Run the executable:

Linux/macOS

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1./hello

Windows

cmdCopy
1hello.exe

Output:

textCopy
1Hello, World!

Compilation Process

When you compile a C program, it goes through several stages.

Source Code (.c)
        │
        ▼
Preprocessor
        │
        ▼
Compiler
        │
        ▼
Assembler
        │
        ▼
Object File (.o/.obj)
        │
        ▼
Linker
        │
        ▼
Executable Program

1. Preprocessor

Processes directives such as:

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1#include
2#define

2. Compiler

Converts C code into assembly language.

3. Assembler

Converts assembly language into machine code (object files).

4. Linker

Combines object files and required libraries into the final executable.

Comments in C

Comments improve readability and explain the purpose of code.

The compiler ignores comments.

Single-Line Comment

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1// This is a single-line comment

Example:

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1// Display welcome message
2printf("Welcome");

Multi-Line Comment

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1/*
2This is a
3multi-line comment.
4*/

Example:

cCopy
1/************************************************
2Program : Calculator
3Author  : John
4Date    : 2026
5************************************************/

Best Practices for Comments

• Explain why code exists, not what every line does.
• Keep comments up to date.
• Avoid unnecessary comments for obvious code.
• Use descriptive block comments for files and complex functions.

Practice Project 1: Hello World

cCopy
1#include <stdio.h>
2
3int main()
4{
5    printf("Welcome to C Programming!\n");
6    return 0;
7}

Practice Project 2: Simple Calculator

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int a, b;
6
7    printf("Enter two numbers: ");
8    scanf("%d %d", &a, &b);
9
10    printf("Addition = %d\n", a + b);
11    printf("Subtraction = %d\n", a - b);
12    printf("Multiplication = %d\n", a * b);
13
14    if (b != 0)
15        printf("Division = %.2f\n", (float)a / b);
16    else
17        printf("Division by zero is not allowed.\n");
18
19    return 0;
20}

Practice Project 3: Student Information

cCopy
1#include <stdio.h>
2
3int main()
4{
5    char name[50];
6    int age;
7    float marks;
8
9    printf("Enter Name: ");
10    scanf("%49s", name);
11
12    printf("Enter Age: ");
13    scanf("%d", &age);
14
15    printf("Enter Marks: ");
16    scanf("%f", &marks);
17
18    printf("\n----- Student Information -----\n");
19    printf("Name  : %s\n", name);
20    printf("Age   : %d\n", age);
21    printf("Marks : %.2f\n", marks);
22
23    return 0;
24}

Module Summary

In this module, you learned:

• What programming is and why it matters.
• What the C programming language is and its historical background.
• Key features that make C powerful and widely used.
• Real-world applications of C in operating systems, embedded systems, databases, and networking.
• How to install the GCC compiler on Windows, Linux, and macOS.
• How to write, compile, and run your first C program.
• The stages of the C compilation process.
• How to use single-line and multi-line comments effectively.
• How to build simple beginner projects such as a Hello World application, a basic calculator, and a student information program.

This foundation prepares you for the next module, where you'll explore variables, data types, input/output, constants, and operators in C.