Introduction to C Programming

1. What is a Program?

Computers cannot normally perform a task simply by understanding human language. We write instructions using a programming language, such as C, C++, Java or Python.

Simple Example

Suppose we want a computer to add two numbers. We can give it instructions such as:

1. Store the first number.
2. Store the second number.
3. Add the two numbers.
4. Display the result.

2. What is Software?

A software application may contain many programs, files, libraries, menus and other components working together.

Program vs Software

3. People Involved in Software

4. History of C Language

5. Features of C Language

6. Hardware Platform and Software Platform

Hardware Platform

A hardware platform refers to the physical computer system on which software runs.

Important hardware components include:

• Processor (CPU)
• RAM
• Motherboard
• Storage devices
• Other hardware components

Software Platform

A software platform commonly includes the operating system and related system software that provides an environment for programs to run.

Examples of operating systems include:

• Windows
• Linux
• macOS

7. Minimum C Program

A C program normally contains a main() function. Program execution begins from the main() function.

Modern Standard Form

#include <stdio.h>

int main(void)
{
    /* Program statements go here */

    return 0;
}

Understanding the Program

8. Example – A Simple C Program

#include <stdio.h>

int main(void)
{
    printf("Welcome to C Programming");

    return 0;
}

Output

9. Common Parts of a C Program

A C program can contain several important elements. Three commonly encountered elements are:

1. Statements
2. Comments
3. Functions

10. Statements

Examples

int x;
x = 10;
printf("%d", x);

Types of Program Statements

11. Preprocessor Directives

Examples include #include and #define.

Example 1 – #include

#include <stdio.h>

This tells the preprocessor to include the declarations provided by the standard input/output header.

Example 2 – #define

#define MAX 100

This defines the symbolic constant MAX as 100 for preprocessing purposes.

12. Compound Statement / Block

Example

{
    int x;
    x = 10;
    printf("%d", x);
}

Blocks are commonly used as the bodies of functions, loops, conditional statements and other control structures.

13. Functions

Functions help divide a large program into smaller, manageable parts.

Example

#include <stdio.h>

void welcome(void)
{
    printf("Welcome!");
}

int main(void)
{
    welcome();

    return 0;
}

In this example, welcome() is a user-defined function. The main() function calls it using:

14. Comments in C

Comments are useful for programmers because they make source code easier to understand, maintain and modify.

Two Styles of Comments

14.1 Single-Line Comment

// This program displays a welcome message

#include <stdio.h>

int main(void)
{
    printf("Welcome to C Programming");

    return 0;
}

14.2 Multi-Line Comment

/*
    This program demonstrates
    the use of comments
    in a C program.
*/

#include <stdio.h>

int main(void)
{
    printf("Hello");

    return 0;
}

Why Use Comments?

• Explain what a section of code does.
• Make programs easier to read.
• Help programmers maintain code.
• Document important logic or assumptions.
• Temporarily disable a section of code during debugging.

15. Comment Shortcuts in Code::Blocks

16. Anatomy of a Simple C Program

// Program to display a message

#include <stdio.h>

int main(void)
{
    printf("Hello, C Programming!");

    return 0;
}

17. From Programmer to End-User

18. Practice Questions

A. Multiple Choice Questions

B. Short Answer Questions

C. Programming Practice

D. Identify the Parts

// Addition of two numbers

#include <stdio.h>

int main(void)
{
    int a, b;

    a = 10;
    b = 20;

    printf("%d", a + b);

    return 0;
}

19. Debugging Practice

Find and correct the errors in the following program.

#include <stdio.h>

int main(void)
{
    int x

    x = 10

    printf("%d", x);

    return 0;
}

20. Quick Revision