c programming codetantra 1.1

1.1.1 Introduction to a Computer

Definition

A computer is an electronic device that:

  1. Receives input (data from a keyboard, mouse, file, sensor, etc.)

  2. Processes it (using instructions given by the user/program)

  3. Gives output (in the format you want — screen display, printed paper, saved file, etc.)

Why Computers Are Useful

  • They can do simple and very complex tasks.

  • They can repeat tasks without getting tired.

  • They rarely make mistakes (if the instructions are correct).

Input-Process-Output Model

This is the basic workflow:

Input  --->  Process  --->  Output

Example:

  • Input: You type 2 + 3

  • Process: Computer adds numbers

  • Output: Shows 5 on the screen

Clarifications

  • Computers are electronic devices (not just “electrical” — electronic means they use logic circuits with microchips).

  • Processing is a core function, but without input and output, the computer wouldn’t be useful.

Tip: Whenever you’re thinking about how a program or device works, try to map it to:

  1. What’s the input?

  2. What’s the process?

  3. What’s the output?






SIMPLIFIED NOTES

1.1.1 Introduction to a Computer

  • A computer is an electronic device.

  • It takes input, processes it as per instructions, and gives output.

  • Uses the Input → Process → Output (IPO) Model.

  • Can do both simple and complex tasks repeatedly without errors.

Key Points for Exam

  • Computer = electronic device (not electrical).

  • Main workflow = Input → Process → Output.

  • Processing = most important function.

Correct Statements

  1. Computers can perform easy and complex tasks repeatedly without committing errors. ✔

  2. Computers are electrical devices ❌ (Correct = electronic devices).

  3. Processing is the most important function performed by the computer ✔

1.1.2 Different Components of a Computer System

1. Input Unit

  • Devices used to give data/instructions to the computer.

  • Connects user → computer.

Examples: Keyboard (typing), Mouse (point & click), Scanner (convert images to digital), Joystick (games).

Key Points for Exam:

  • Input unit = link between user and computer.

  • Keyboard = most common input device.

  • Mouse = pointing device.

2. Central Processing Unit (CPU)

  • Known as the brain of the computer.

  • Executes instructions and controls all operations.

  • 3 main parts: Memory Unit, Control Unit, ALU.

a) Memory Unit (Storage Unit)

  • Stores data, instructions, and results.

  • Primary memory (Main memory):

    • RAM – temporary, data lost when power off.

    • ROM – permanent, stores BIOS.

    • Cache – very small, very fast memory near CPU.

  • Secondary memory (External): Hard disk, CD, DVD, USB.

Key Points:

  • RAM = temporary, read/write.

  • ROM = permanent, read-only.

  • Cache = small + fast, near CPU.

  • Secondary = long-term storage.

b) Control Unit (CU)

  • Directs and controls all computer operations.

  • Transfers data among units.

  • Communicates with Input/Output devices.

Key Points:

  • CU = “traffic controller” of computer.

  • Does NOT process data, only controls.

c) Arithmetic Logic Unit (ALU)

  • Performs calculations and logical operations.

  • Arithmetic: +, –, ×, ÷.

  • Logic: comparisons (>, <, =), decisions.

Key Points:

  • ALU = calculator + decision maker.

3. Output Unit

  • Devices that show results to the user.

  • Converts computer’s digital output → human-readable form.

Examples:

  • Monitor (screen display).

  • Printer (hard copy – Dot matrix, Inkjet, Laser).

  • Speaker (sound output).

  • Plotter (large drawings).

Key Points:

  • Output = link between computer and user.

  • Printers = hardcopy devices.

Correct Statement Question

  1. CPU means Central Programming Unit ❌

  2. CPU means Central Processing Unit ✔

  3. Primary memory includes RAM and Cache memory ✔

  4. RAM means Random Available Memory ❌ (Correct = Random Access Memory)

✅ Final Key Exam Points Recap:

  • CPU = brain → Memory, Control Unit, ALU.

  • Input = user → computer, Output = computer → user.

  • RAM = temporary, ROM = permanent, Cache = very fast.

  • CU = controls, ALU = calculates & compares.


1.1.3 Characteristics of a Computer

  1. Speed – Performs operations very fast.

  2. Accuracy – Very accurate, errors usually come from humans (wrong input/instruction).

  3. Reliability – Can repeat the same work without errors.

  4. Versatility – Can do many different tasks (from simple storage → complex calculations).

  5. Storage Capacity – Can store huge amounts of data.

Key Points for Exam

  • Computers = fast + accurate + reliable.

  • Errors mainly come from human input, not from the computer itself.

  • Very versatile, large storage.

Correct Statements

  1. Computers can carry out the same type of work repeatedly without throwing up errors. ✔

  2. There are more chances for errors when a computer performs the same task again for a second time. ❌


1.1.4 Computer Booting

  • Booting = Process of starting a computer.

  • Steps:

    1. Power on → supply electricity.

    2. Load Operating System (OS) into main memory.

    3. Applications ready for use.

  • BIOS (Basic Input Output System):

    • First program that runs when computer starts.

    • Permanently stored in hardware (firmware).

Types of Booting

  1. Cold Booting – Starting the system by switching on power. BIOS is loaded.

  2. Warm Booting – Restarting the system when it is already running. Faster (BIOS not reloaded).

Rebooting = restarting the system.

Correct Statements

  1. When the system is started by switching on the power supply it is called cold booting. ✔

  2. The first program (set of instructions) that runs when the computer is switched on is called BIOS. ✔

  3. When the system is already running and needs to be restarted or rebooted, it is called warm booting. ✔


1.1.5 Evolution of Computers

Computers evolved in 5 generations – each marked by a major technology change.

1. First Generation (1940–1956)

  • Technology: Vacuum tubes.

  • Memory: Magnetic drums.

  • Language: Machine language.

  • Input/Output: Punch cards, paper tape → printouts.

  • Examples: ENIAC, UNIVAC.

2. Second Generation (1956–1963)

  • Technology: Transistors.

  • Smaller, faster, less power than vacuum tubes.

  • Languages: Assembly + early high-level (COBOL, FORTRAN).

  • Memory: Magnetic core.

3. Third Generation (1964–1971)

  • Technology: Integrated Circuits (ICs).

  • Faster, more efficient.

  • Input/Output: Keyboards + monitors.

  • Operating system introduced (multiple applications).

4. Fourth Generation (1972–2010)

  • Technology: Microprocessors (Intel 4004).

  • All CPU parts on a single chip.

  • PCs developed (IBM 1981, Apple Macintosh 1984).

  • Networking → Internet.

5. Fifth Generation (2010 onwards)

  • Technology: Artificial Intelligence, Quantum computing, Nanotech.

  • Goal: Natural language understanding, self-learning, smarter systems.

Correct Statements

  1. First generation computers used vacuum tubes. ✔

  2. Integrated circuits were used in the second generation computers. ❌ (Correct = third generation).

  3. Microprocessors were first introduced in the third generation of computers. ❌ (Correct = fourth generation).

  4. Keyboards and monitors were introduced as input output devices from the second generation computers. ❌ (Correct = third generation).

Evolution of Computers – One Line Tricks

  1. First Generation (Vacuum Tubes)
    Trick: “Vacuum = Very big, very slow, very hot.”
    (Think of vacuum tubes as bulbs → heat + large size).

  2. Second Generation (Transistors)
    Trick: “Tiny Transistors take over Tubes.”
    (Remember: transistors replaced vacuum tubes → smaller, faster).

  3. Third Generation (Integrated Circuits)
    Trick: “IC = Input Comes (Keyboard + Monitor).”
    (ICs also → faster + OS introduced).

  4. Fourth Generation (Microprocessors)
    Trick: “Micro = My PC is born.”
    (Remember: IBM PC, Apple Macintosh → personal computers).

  5. Fifth Generation (AI)
    Trick: “AI = Actually Intelligent.”
    (Remember: AI, Quantum computing, self-learning machines).

Quick Timeline Strategy

  • 1st (1940s) – Bulky vacuum tubes.

  • 2nd (1950s) – Transistors = smaller.

  • 3rd (1960s) – ICs + monitor/keyboard.

  • 4th (1970s–2000s) – Microprocessor → PCs, Internet.

  • 5th (2010+) – AI + Quantum future.

👉 Super-Short Exam Line:
“Very Tiny ICs Made AI.”
(Vacuum → Transistor → IC → Microprocessor → AI).


1.2.1. What is a computer programming language?

  • A language used to give instructions to a computer.

  • Just like English/Spanish is for humans, programming languages are for computers.

  • Example: In C

    #include <stdio.h>
void main() {
    printf("Hello!");
}

  • This code tells the computer to print Hello!

Key Points for Exam:

  • Programming language = way to instruct computer.

  • Source code = sequence of instructions.

  • C is an imperative (procedure-based) and structured language.

1.2.2. A simple program in C

  • A basic C program can display messages.

  • Example:

    #include <stdio.h>
void main() {
    printf("Hello C\n");
}

  • Output: Hello C

Key Points:

  • #include <stdio.h> allows use of printf.

  • main() = entry point of program.

  • \n = new line.

1.2.3. The Genesis of C

  • Created in 1972 by Dennis Ritchie at AT&T Bell Labs.

  • Influenced by B and BCPL languages.

  • Standardized by ANSI in 1983.

  • C = Middle-level language (both high-level and low-level features).

Key Points:

  • Year: 1972

  • Creator: Dennis Ritchie

  • Category: Middle-level

  • Used for: OS, applications, embedded systems

1.2.4. Life Cycle of a C Program

  1. Write code → save as .c file (source code).

  2. Compiler → converts to .obj (object file with machine code).

  3. Linker → combines object files into executable (.exe).

  4. Run executable → get output.

Key Points:

  • Source code: .c

  • Compiler output: .obj

  • Linker output: executable (e.g., .exe)

  • Linking happens after compilation.

1.2.5. Modifying a C Program

  • You can change the text inside printf() to modify program output.

  • Example:

    printf("I love Mangoes\n");

  • \n makes output go to a new line.

Key Points:

  • Change text inside quotes to change output.

  • \n = line break.

1.2.6. Structure of a Simple C Program

Example:

#include <stdio.h>
void main() {
    printf("Hello!");
}

  • #include <stdio.h> = adds standard input/output functions.

  • void main() = main function, returns nothing.

  • printf() = prints text to screen.

  • { } = contain program statements.

Key Points:

  • #include = preprocessor command.

  • main() is starting point.

  • printf("Text") prints text.

1.2.7. Understanding Comments in C

  • Comments = text ignored by compiler.

  • Used for explanations.

  • Types:

    • Single-line: // comment

    • Multi-line:

      /* comment */

Key Points:

  • Comments are non-executable.

  • Cannot nest comments.

  • Useful for explaining code.

1.2.8. Example of Comments

#include <stdio.h>
void main() {
    printf("Orange\n");
    //printf("Mango\n");
    printf("Banana\n");
}

  • Mango is commented out, so not printed.

  • Output:

    Orange
Banana

1.2.9. Escape Sequences in C

  • Special symbols starting with \.

  • Examples:

    • \n → new line

    • \t → tab space

    • \" → double quote

  • Example:

    printf("One\tTwo");
printf("Three\n");

    Output:

    One     Two
Three

Key Points:

  • Escape sequence starts with \.

  • Represent single special characters.

1.2.10. Writing Escape Characters

#include <stdio.h>
void main() {
    printf("Dennis\tRitchie\nBrian\tKernighan\n");
}

Output:

Dennis    Ritchie
Brian     Kernighan

Key Points:

  • \t = tab

  • \n = new line

  • Used to format output neatly.









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