Unit 1: Computer Systems Class 9 Computer Science - Federal Board | FBISE

Unit 1: Introduction to Computer Systems
Early Computing Devices
Generations of Computers
What is a System?
Natural Systems
Artificial Systems
Core Components of a Computer System
Von Neumann Architecture
Computer Memory Study Guide
Software and Hardware Engineering
Programming Languages
Data Communication and Networking

Unit 1: Introduction to Computer Systems

Definition: A computer is a programmable electronic device that automatically performs arithmetic and logical operations based on user instructions.
System Composition: It is a sophisticated combination of hardware and software components working together to process information and solve problems.
Impact: Computer systems have revolutionized how humans work, communicate, learn, and entertain themselves.

Early Computing Devices

Before modern computers, humans used tools like sticks, stones, and bones for counting. Key historical developments include:

Abacus: An ancient tool using beads on rods for arithmetic.
Napier's Bones: Invented by John Napier; used numbered strips for multiplication, division, and introduced the decimal system.
Pascaline (1642): A mechanical calculator by Blaise Pascal using gears and wheels.
Stepped Reckoner (1673): Invented by Wilhelm Leibniz for advanced calculations.
Difference Engine (1820s): A steam-powered machine by Charles Babbage for numerical problems.
Analytical Engine (1830s): Babbage's improved design for general-purpose computation, storage, and punch card input.
Tabulating Machine (1890): Invented by Herman Hollerith; used punch cards to compute statistics (foundation for IBM).
Mark I (1944): An electromechanical computer by Howard Aiken capable of adding three 8-digit numbers per second.

Generations of Computers

1. First Generation (1940–1956)

Core Technology: Vacuum tubes.
Characteristics: Large, expensive, slow, unreliable, and prone to overheating.
Programming: Limited to machine language.
Input/Output: Punched cards and printouts.
Examples: ENIAC, UNIVAC I, IBM 604.

2. Second Generation (1956–1963)

Core Technology: Transistors (replaced vacuum tubes).
Characteristics: Smaller, faster, more reliable, and cost-effective.
Programming: Advanced to assembly and high-level languages (FORTRAN, COBOL).
Input/Output: Magnetic tapes, disks, and punched cards.
Examples: UNIVAC II, IBM 7030, CDC 1604.

3. Third Generation (1963–1971)

Core Technology: Integrated Circuits (ICs).
Characteristics: Significant increase in speed and efficiency; introduced keyboards and monitors.
Capabilities: Able to run multiple applications simultaneously.
Examples: IBM System/360, CDC 6600.

4. Fourth Generation (1971–Present)

Core Technology: Microprocessors (LSI and VLSI technologies).
Characteristics: Exceptional speed, compact size, and large storage capacities.
Features: Standardized Graphical User Interfaces (GUIs) and multimedia.
Programming: Supports modern languages like C++, Java, and Python.
Portable Devices: Led to the rise of laptops and smartphones.
Examples: Intel Pentium series, Apple MacBook Pro, Dell Inspiron.

5. Fifth Generation (Present and Beyond)

Focus: Artificial Intelligence (AI) and Natural Language Processing (NLP).
Characteristics: Capable of learning, reasoning, and autonomous problem-solving.
Advanced Features: Parallel processing, voice recognition, and gesture control.
Applications: Expert systems and ROBOTS used in medicine and engineering.

What is a System?

A system is a collection of interconnected components working together to achieve specific goals.

Inputs: The system receives materials or data.
Processes: The system acts on the inputs.
Outputs: The system produces desired results.

Natural Systems

These systems occur organically in nature and function without human intervention.

Core Characteristics: They are self-regulating, stable, and highly adaptable.
Interconnectivity: Elements work harmoniously and are often highly intricate.
Sustainability: Usually long-lasting and vital to life and ecology.
Evolution: They change through natural selection over time and are governed by natural laws (e.g., physics and biology).
Examples: Forests, rivers, weather patterns, the solar system, and the human body.

Artificial Systems

These are human-designed and built to solve specific problems or fulfill needs.

Intentional Design: Created by humans and often simpler than natural systems.
Maintenance: Dependent on human intervention and resource availability to remain functional.
Rules: Operate under predefined, human-set rules rather than autonomous natural laws.
Modification: Can be modified or innovated rapidly by humans but require manual updates to adapt.
Examples: Computers, vehicles, power grids, communication networks, and medical devices.

Key Differences at a Glance

Feature	Natural Systems	Artificial Systems
Energy Source	Natural (sunlight, water flow)	Artificial (electricity, fuel)
Complexity	Highly intricate	Relatively simpler
Adaptation	Autonomous evolution	Requires human redesign
Purpose	Life and ecological roles	Specific human purposes

Core Components of a Computer System

A computer system consists of several essential components working together to perform tasks:

Input devices: For entering data and instructions.
System unit: Houses the motherboard, CPU, memory, and power supply.
Storage devices: For long-term or temporary data retention.
Output devices: For providing processed data in various formats.

Input Devices

These allow users to provide data and instructions, facilitating human-computer interaction.

Keyboard: Primary device for entering text, numbers, and symbols.
Mouse: Hand-held device used to control the screen pointer and navigate files.
Microphone: Converts sound into digital signals for voice commands or recording.
Scanner: Converts physical documents or images into digital format.
Barcode Reader: Scans product codes to extract data like price and inventory details.
Digital Camera: Captures photographs and videos for digital use.
Touch Screen: Dual-purpose device allowing direct interaction through gestures.

System Unit

The central hub that houses internal components and connects all input/output devices.

The Motherboard

The main circuit board and backbone of the computer.
Contains the microprocessor, memory slots, and expansion slots to ensure communication between parts.

The Microprocessor (CPU)

Known as the "brain" of the computer, it executes instructions via three main components:

Arithmetic Logic Unit (ALU): Performs mathematical operations and logical comparisons.
Control Unit (CU): Manages system activities and directs the execution of instructions.
Registers: Small, temporary storage spaces used during processing.

Storage Devices

Used to hold data and programs ranging from internal drives to portable media.

Hard Disk: Magnetic storage for primary data and operating systems (GB to TB range).
SSD (Solid State Drive): Modern, faster, and more durable storage using integrated circuits.
Optical Media: Includes CDs (700 MB) and DVDs (up to 16 GB).
Memory Card: Small, portable storage used in mobile phones and cameras.
USB Flash Drive: Compact, portable device connected via USB ports.

Output Devices

Devices that display or provide the results of processed data.

Monitor: Displays visual information; modern versions use LCD/LED technology.
Printer: Creates "hard copies" of documents.
- Impact Printers: Use mechanical action (e.g., dot matrix).
- Non-Impact Printers: Faster, higher-quality (e.g., inkjet and laser).
Plotter: Used for large-scale graphics like engineering designs and maps.
Speakers: Convert digital signals into audio for music, gaming, and video.

Ports, Expansion Slots, and Cards

These components allow for the connection and enhancement of computer capabilities.

Ports: Interfaces for connecting peripherals (e.g., USB, HDMI, VGA, LAN, and Audio jacks).
Expansion Slots: Sockets on the motherboard where additional hardware can be installed.
Expansion Cards: Circuit boards inserted into slots to add functionality, such as sound, graphics, or network cards.

Von Neumann Architecture

Definition: A fundamental computer science concept (1945) explaining how hardware and software work together.
Stored-Program Concept: A design where program instructions and data are stored in the same memory.
Main Components: CPU, Memory Unit (RAM), Busses, I/O Controllers, and Secondary Storage.

The Central Processing Unit (CPU)

The CPU is the electronic circuit responsible for executing instructions. It contains:

Control Unit (CU): Manages the ALU, memory, and I/O. It decodes instructions and provides timing signals.
Arithmetic and Logic Unit (ALU): Performs calculations (add, subtract) and logical operations (AND, OR, NOT).
Registers: Small, high-speed storage areas within the CPU.

Key CPU Registers

Register	Name	Function
MAR	Memory Address Register	Holds the memory location of data to be accessed.
MDR	Memory Data Register	Holds data being transferred to or from memory.
AC	Accumulator	Stores intermediate arithmetic and logic results.
PC	Program Counter	Contains the address of the next instruction to be executed.
CIR	Current Instruction Register	Contains the instruction currently being processed.

Memory and Storage

Memory Unit: Consists of RAM and Cache. It is fast and directly accessible by the CPU.
Memory Hierarchy (Fastest to Slowest):
1. Cache
2. RAM
3. Storage Devices (SSD, HDD)

Bus System

Buses are pathways for transmitting data between components.

Address Bus: Carries memory addresses (where the data is) between processor and memory.
Data Bus: Carries the actual data/instructions between the processor, memory, and I/O.
Control Bus: Carries commands and signals from the CPU to coordinate activities.

Data Transmission & Processing

1. The Instruction Cycle

Fetch: Get the instruction from memory.
Decode: Interpret the instruction via the CU.
Execute: Carry out the operation.

2. Efficiency Concepts

Pipelining: Processing multiple instructions simultaneously by breaking them into stages.
Interrupts: Signals from devices (like keyboards) that pause the CPU to handle important events.
Data Paths: Internal pathways connecting CPU components like the ALU and CU.

Computer Memory Study Guide

            Core Definition
            Computer Memory refers to the physical devices used to store programs (sequences of instructions) and data.
It can store information on a temporary or permanent basis.
It holds the main part of the operating system and all active application programs.

        

1. Memory Terminology

Bit: The smallest unit of memory, representing a binary digit (0 or 1).
Byte: A group of 8 bits. It is the smallest unit a computer can process and typically stores one character.
Memory Word: The smallest unit of data a computer can process in a single operation.
Word Size: The number of bits a CPU can handle in one instruction (e.g., 32-bit or 64-bit). A larger word size improves speed and memory capacity.

Memory Units Table

Memory Unit	Equivalent To
1 Kilobyte (KB)	1024 Bytes (2¹⁰ Bytes)
1 Megabyte (MB)	1024 KB (2²⁰ Bytes)
1 Gigabyte (GB)	1024 MB (2³⁰ Bytes)
1 Terabyte (TB)	1024 GB (2⁴⁰ Bytes)
1 Petabyte (PB)	1024 TB (2⁵⁰ Bytes)
1 Exabyte	1024 PB (2⁶⁰ Bytes)

2. Classification of Memory

Types based on Construction (Built-Up)

Chip Memory: Built using semiconductor technology; fast and compact.
- Examples: RAM, ROM, Flash memory.
Magnetic Memory: Stores data on magnetized materials; ideal for large-scale storage.
- Example: Hard Disk Drives (HDDs).
Optical Memory: Uses laser technology to read/write data as tiny pits on discs.
- Examples: CDs, DVDs, Blu-ray Discs.

Types based on Retention Power

Volatile Memory: Requires power to retain data. Information is lost when power is off.
- Examples: RAM, Cache, Registers.
Non-Volatile Memory: Retains data even when power is off.
- Examples: ROM, Flash drives, HDDs.

3. Memory Hierarchy

Memory is organized to balance speed, size, and cost. Faster types (Main Memory) are smaller and closer to the CPU, while slower types (Secondary Memory) are larger and used for storage.

Main Memory (Primary Memory)

RAM (Random Access Memory): High-speed volatile memory installed on the motherboard. It is "Read/Write" memory used for active programs.
ROM (Read Only Memory): Non-volatile IC chip that stores the BIOS (Basic Input/Output System) to control the boot process.
Internal Processor Memory:
- Cache Memory: Small, extremely fast memory near the CPU that stores frequently accessed data.
  - L1: Smallest/fastest, located in the processor core.
  - L2: Larger/slower than L1, located in the CPU or motherboard.
  - L3: Largest/slowest cache, shared among multiple cores.
- Registers: The smallest and fastest units inside the processor, used for immediate data and instructions during computations.

Secondary Memory

Used for long-term storage and remains intact when power is off.

Chip-Based: Semiconductor solutions like SSDs, USB drives, and Memory cards.
Magnetic Storage: Uses magnetized surfaces. It is cost-effective for vast amounts of data but has slower access speeds (e.g., Hard Disks).
Optical Storage: Uses lasers to encode data into tiny "pits" and "lands" on tracks. It offers higher capacity than magnetic storage for things like encyclopedias or software distribution.

Study Guide: Software and Hardware Engineering

1. Software Engineering vs. Hardware Engineering

Software Engineering: A systematic approach to the development, operation, and maintenance of software using engineering principles to ensure quality and reliability.
- Application Software Engineering: Developing apps for specific user needs (e.g., web, mobile, desktop).
- System Software Engineering: Creating platforms for other software to run on (e.g., operating systems, compilers).
- Embedded Software Engineering: Specialized software for hardware devices like automotive systems or home appliances.
- Enterprise Software Engineering: Large-scale solutions to automate business processes and manage data.
- Game Development: Creating video games, including graphics, audio, and gameplay programming.
Hardware Engineering: Designing, developing, and testing physical components like processors, circuit boards, and sensors.
- Digital Hardware Engineering: Designing digital circuits and components like memory units.
- Analog Hardware Engineering: Dealing with analog circuits such as amplifiers.
- Integrated Circuit (IC) Design: Designing and fabricating chips like CPUs and GPUs.
- Computer Architecture: Designing the structure and organization of computer systems.
- Embedded Systems Design: Designing hardware integrated into larger devices, such as microcontrollers.

2. Computer Software

A collection of programs, data, and instructions that tell a computer how to function. It is categorized into two main types:

1.8.1 System Software

Software that manages hardware and provides a platform for applications.

Operating System (OS): Manages hardware resources (CPU, memory, files) and provides a user interface. Examples: Windows, macOS, Linux, Android.
Device Drivers: Facilitate communication between the OS and hardware (e.g., printers, graphics cards).
Utilities: Tools for maintenance tasks like disk cleanup, virus scanning, and data backup.
Compiler and Assembler:
1. High-level Program (e.g., C++, Java) is written.
2. Compiler translates source code into executable programs.
3. Low-level Program (machine code) is produced for the processor.
Linkers and Loaders: Linkers combine object files into one executable; Loaders load them into memory.
Firmware: Software permanently stored on hardware (e.g., BIOS).

1.8.2 Application Software

Programs designed for users to perform specific tasks, often called "apps."

Productivity Software: For document creation and collaboration (e.g., Microsoft Office, Google Workspace).
Business Software: For managing financial transactions or projects (e.g., QuickBooks, Trello).
Entertainment Software: For leisure (e.g., Minecraft, Netflix, Spotify).
Educational Software: Supports learning and skill development (e.g., LMS platforms, Duolingo, Kahoot!).

Programming Languages

Programming languages are tools used to instruct computers to perform specific tasks. They are categorized into two main types: Low-Level and High-Level.

Low-Level Languages

These are machine-oriented languages closely tied to a computer's physical architecture. They are divided into two types:

Machine Language:
- Uses binary code (0s and 1s).
- Directly understood by hardware.
- Highly complex and dependent on specific computer architecture.
Assembly Language:
- Uses symbolic codes (mnemonics) like MOV and ADD.
- Requires an assembler to convert code into machine language.
- Offers faster execution and access to specific hardware features.

Uses of Low-Level Languages

System Development: Creating operating systems and firmware.
Hardware Interaction: Developing device drivers and programming embedded systems (IoT).
Performance-Critical Tasks: Real-time systems (robotics, aerospace), security tools (firewalls), and game engine optimization.

High-Level Languages (HLLs)

These are user-friendly languages that resemble English, making them easier to learn and debug. Programs must be converted into machine language using a compiler or interpreter. HLLs are classified into three categories:

Procedural Languages: Focus on a sequence of instructions or procedures. Programs are broken into modules or functions (e.g., C, Pascal).
Structured Languages: Use logical structures like conditional statements and loops to improve readability (e.g., FORTRAN, ALGOL).
Object-Oriented Languages: Organize code around "objects" representing real-world entities with attributes and behaviors (e.g., Java, C++, Python).

Uses of High-Level Languages

Software Development: Building desktop, mobile, and web applications.
Data & AI: Data analysis, scientific research, and Machine Learning/AI algorithms.
Management & Automation: Database management, business software, and system administration scripting.
Simulation: Scientific and engineering simulations or game logic development.

Data Communication and Networking

1.9 Data Communication

Definition: The process of exchanging data or information between two or more systems via a transmission medium (cables, optical fibers, or wireless).

1.9.1 Network Communication Components

Communication consists of five basic components:

Sender (Transmitter): The device (computer, workstation, phone, camera) that sends the message. It converts electrical signals into a form suitable for transmission.
Message: The actual data or information being transmitted (text, audio, video, etc.).
Medium: The path through which the message travels.
- Wired: Telephone cable, coaxial cable, fiber optics.
- Wireless: Wi-Fi, Bluetooth, microwave, radio waves, satellite.
Receiver: The device that receives the message. It may need to convert the data back into a usable form.
Protocol: A set of rules and agreements that govern data communication between devices.

1.9.2 Modes of Network Communication

Refers to the ways information is transmitted from one place to another:

Simplex Mode: Unidirectional communication (one direction only).
- Example: Information sent to an electronic notice board or from a computer to a printer.
Half-Duplex Mode: Bi-directional, but not at the same time. Only one party can send or receive at a single moment.
- Example: Walkie-talkies.
Full-Duplex Mode: Bi-directional and simultaneous. Both parties can send and receive at the same time.
- Example: Telephone networks.

Transmission Timing

Asynchronous Transmission: Data is sent with variable time intervals. It uses Start bits (to alert the receiver) and Stop bits (to signal the end of a character).
Synchronous Transmission: Data is sent as a continuous bit stream with consistent time intervals. It is faster as it does not require start/stop bits.

1.9.3 Communication Devices

Devices used to transmit data across systems:

Hub: A basic device that broadcasts data to all connected devices in a LAN. It is simple but inefficient.
Switch: A more intelligent device that inspects data packets and sends them only to the correct recipient, reducing traffic.
Router: Links multiple networks (e.g., a LAN to the internet) and determines the best path for data packets.
Gateway: Acts as a "translator" between different types of networks using different protocols (e.g., connecting a PC network to a mainframe).

1.9.4 Network Architecture

The design and structure of a communication system, defining the roles of computers:

Client/Server Network:
- Server: A computer that provides resources (files, software, hardware) to others.
- Client: A computer that requests and uses resources from the server.
- Advantage: Centralized control and enhanced security.
Peer-to-Peer (P2P) Network: Every computer acts as both a client and a server. Typically used for small groups (2–10 computers).

1.9.5 Types of Networks

Local Area Network (LAN): Connects devices within a small area (home, office, building). High speed and reliable.
Metropolitan Area Network (MAN): Spans a city or large campus (5 to 50 km). Used by ISPs and cable TV companies.
Wide Area Network (WAN): Covers large distances, countries, or the globe (e.g., the Internet). Uses public networks, satellites, or leased lines.

1.9.6 Wireless Networks

Uses wireless technologies for flexibility and mobility. Examples include Wi-Fi, Bluetooth, Cellular Networks, and Satellite Networks.

Advantages: Access from any location, easier/cheaper to install than wires, supports work from home.
Disadvantages: Signals can be disrupted, higher risk of data breaches, can be slower in crowded areas.

1.9.7 Network Topologies

The physical or logical layout of a network:

Bus Topology: All devices connect to a single central cable. Simple and cost-effective but fails if the main cable is damaged.
Star Topology: Each device connects to a central hub or switch. Easy to maintain, but if the hub fails, the whole network goes down.
Ring Topology: Devices are connected in a circular fashion. Data travels in one direction. A single break can bring down the network.

1.9.8 Transmission Technologies

Packet Switching: Data is divided into small packets sent independently through different routes and reassembled at the destination (e.g., Email).
Circuit Switching: Establishes a dedicated, continuous communication path for the duration of a session (e.g., traditional phone calls).

1.9.9 & 1.9.10 The OSI Model

A conceptual framework consisting of seven layers to standardize networking:

Application Layer: Provides services to end-users (file transfers, messaging).
Presentation Layer: Translates data formats to ensure compatibility.
Session Layer: Manages and secures communication sessions.
Transport Layer: Ensures reliable data transfer and packet integrity.
Network Layer: Determines the optimal path for transmission (routing).
Data Link Layer: Defines data format into packets and verifies accuracy.
Physical Layer: Deals with physical transmission via hardware (cables, connectors).

1.9.11 Data Communication Protocols

TCP/IP: Used for reliable internet communication.
HTTP: Used for transferring web pages.
FTP: Used for transferring files between computers.
SMTP: Used for sending email messages.

1.9.12 The Internet

A global, decentralized network of interconnected networks using packet-switching and TCP/IP protocols.

Evolution: Started as ARPANET (1960s), followed by TCP/IP (1970s), World Wide Web (1990s), Broadband/Social Media (2000s), IoT (2010s), and AI/5G (2020s).
Working: Data is divided into packets, routed via switches/routers, and translated by the Domain Name System (DNS) from human-readable names to IP addresses.

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