1. Introduction to Programming

A computer is a fast, accurate machine, but it can’t think. It waits for humans to give step-by-step instructions. These instructions are called a program, and the person who writes them is a programmer.

A set of programs that helps a computer work is called software. To write programs, we use special languages called programming languages. Just like humans use Nepali or English to talk, computers use languages like C, Java or Python.

2. Types of Programming Languages

a) Machine Language

The oldest, most basic language.

Written using 0s and 1s.

Fastest for the computer but painfully difficult for humans.

b) Assembly Language

• Uses short words called mnemonics (e.g., MOV, ADD).
• Easier than machine language but still low-level.
• Needs an assembler.

c) High-Level Language

Looks more like English.

Easy to write and understand.

Examples: C, Java, Python.

Needs translation:

Compiler

Interpreter

3. Approaches to Programming

To solve problems using a computer, programmers follow some methods.

i. Unstructured Programming

• Everything is written in one long program.
• Uses many jumps (GOTO statements).
• Hard to understand, maintain or debug.

ii. Structured Programming

This is the hero of the chapter.
It breaks the problem into smaller parts called modules.

Features

• Top-down approach
• Uses three main structures:
• Sequence (step-by-step)
• Selection (if-else)
• Loop (repeat until condition is met)
• Makes programs easy to read, test and update.

Advantages

• Less errors
• Easier to understand
• Easier to reuse parts
• Good for team programming

4. Levels of Programming Languages

Programming languages are divided into levels:

a) Lower-Level Languages

Machine and Assembly language

Fast but hard for humans

b) Middle-Level Languages

Provide some low-level control but easier than assembly

Example: C language

c) High-Level Languages

Easy to read and write

Example: Python, Java, C++

5. Introduction to C Language

C is a high-level programming language created by Dennis Ritchie at Bell Laboratories in 1972.

Why is C so popular?

• Fast and powerful
• Can access memory and hardware
• Used to build operating systems
• Portable (runs on many computers)
• Structured (supports modular programming)

Where is C used today?

• Operating systems (like UNIX parts)
• Compilers
• Device drivers
• Embedded systems
• Scientific and engineering applications

6. Features of C Language

• Simple
• Fast execution
• Portable (runs on many computers)
• Structured language
• Middle-level language
• Rich set of operators
• Extensible (allows user-defined functions)
• Efficient memory management

7. Structure of a C Program

A C program always follows a specific pattern.

Parts of a C Program

1. Header files

Tell the compiler what libraries you want to use.

#include

2. main() function

Where the program starts running.

3. Variables

Containers to store data.

4. Statements

Commands that the computer executes.

5. Braces { }

Define the beginning and end of blocks.

8. Data Types in C

To store different kinds of data, C uses data types.

Data TypeSizeExampleint2 or 4 bytes4, 100, -5float4 bytes2.5, 9.81double8 bytes3.1415926char1 byte'A', 'b'

9. Variables and Constants

Variables

Names used to store values that can change.

Example:
int age = 18;

Rules for naming variables

Start with letter or underscore

No spaces

No special symbols

Case-sensitive

Constants

Values that do not change.

Example:
const float PI = 3.14;

10. Operators in C

Operators perform calculations.

a) Arithmetic

+, -, *, /, %

b) Relational

==, !=, >, <, >=, <=

c) Logical

&&, ||, !

d) Assignment

=, +=, -=, *=

11. Input and Output in C

Output: printf()

Used to display data.

Example:
printf("Hello World");

Input: scanf()

Used to get user input.

Example:
scanf("%d", &age);

Format Specifiers

TypeSpecifierint%dfloat%fdouble%lfchar%c

12. Compilation Process in C

Steps from writing to running:

Editing
– Write the program

Compiling
– Convert C code into machine code

Linking
– Link library files

Execution
– Run the final output program

13. Basic Example Program

14. Applications of C Language

C is used in:

1. Operating system development
2. Database systems
3. Network drivers
4. Embedded microcontroller programs
5. Compilers and interpreters
6. Robotics
7. Game engines

15. Limitations of C Language

1. Even superheroes have weaknesses.
2. No built-in graphics support
3. No object-oriented features
4. No automatic garbage collection
5. Harder for beginners to master pointers

16. Why Students Should Learn C

1. Builds strong foundation
2. Helps understand how computers work internally
3. Useful for advanced languages like C++, Java, Python
4. Almost every engineering and CS course starts with C