Comprehensive Study Guide for Hardware, Software, and Computer Systems Components of a Computer System

Hardware: Categories and Internal Components

• Definition of Hardware: The physical components of a computer system.
• External Hardware (Peripherals):     - Keyboard     - Mouse     - Camera     - Monitor     - Printer     - Plotter
• Internal Hardware Components:     - Motherboard:         - A printed circuit board (PCB) found in all computers.         - Connects the processor and other computer hardware, allowing communication.         - Material: Consists of a sheet of non-conductive material like hard plastic.         - Circuits: Thin layers of copper or aluminum printed onto the sheet to form circuits between components.         - Contains several sockets and slots to connect other components.     - Random-Access Memory (RAM):         - Stores data, files, or parts of the operating system currently in use.         - Internal chip where data is stored temporarily during app execution.         - Functionality: Can be written to and read from.         - Volatility: Referred to as volatile or temporary memory; contents are lost when the computer is turned off.     - Read-Only Memory (ROM):         - Stores information that needs to be permanent (e.g., boot files).         - Functionality: Cannot be altered; can only be read from.         - Non-Volatility: Referred to as non-volatile memory; data is not lost when power is turned off.         - Often contains configuration data for the computer system.     - Central Processing Unit (CPU):         - An electronic circuit board that interprets and executes instructions from hardware and software.         - Formerly composed of discrete components on multiple boards; now a single integrated circuit called a microprocessor.         - Found in PCs and household devices (e.g., car engine management systems).         - Components of a CPU:             - Control Unit: Controls input/output devices; takes, decodes, and executes instructions.             - Arithmetic and Logic Unit (ALU): Carries out calculations and makes logical decisions.             - Registers: Small memory locations for immediate use.     - Graphics Card:         - Allows the computer to send graphical information to a monitor, TV, or projector.         - Connects to the motherboard.         - Components: Processing unit, memory unit (mostly RAM), cooling mechanism (heat sink), and display connections.     - Sound Card:         - Integrated circuit board providing the ability to produce sound via speakers or headphones.         - Enables recording via microphone and manipulation of stored sound files.     - Network Interface Card (NIC):         - Allows devices to connect to a network (wired or wireless).         - Hard-coded with a unique Media Access Control (MAC) address code.     - Internal Storage Devices:         - Hard Disk Drives (HDD): Magnetic nature; primary method for storing system/application software and persistent files.         - Solid-State Drives (SSD): Uses flash technology; faster, lighter, and increasingly replacing HDDs in modern computers/tablets.

Software: Applications and Systems

• Definition of Software: Programs that control the computer system and process data.
• Applications Software:     - Provides services for users to solve specific tasks.     - Word Processing: Manages text documents (essays, reports). Features: formatting, creation, editing, spell checkers, thesaurus, image importing, translation.     - Spreadsheet: Organizes numerical data on a grid of lettered columns and numbered rows. Cells identified by coordinates (e.g., B6). Features: formulas, graphing, modelling (‘what if’ calculations).     - Database Management System (DBMS): Organizes, manipulates, and analyzes data using tables of rows (records) and columns (fields). Features: queries, reporting, data modification.     - Control and Measurement Software:         - Control: Compares recorded values to set values to perform actions (e.g., opening a valve).         - Measurement: Measures physical quantities (e.g., temperature) via sensors and stores data.     - Applets vs. Apps:         - Applets: Small applications for a single task, often embedded in HTML/web browsers.         - Apps: Software for substantial tasks (banking, social media); originally developed for mobile phones.     - Video/Audio Editing: Allows manipulation of digital clips. Features: Transitions, color correction, noise reduction, format conversion.     - Graphics Editing:         - Bitmap: Images made of pixels; allows changing brightness/color.         - Vector: Manipulates lines and curves; no pixels used.     - Computer-Aided Design (CAD): Helps create/modify/analyze designs. Features: 3D rotation, full dimensioning, manufacturing cost estimation, structural problem prediction.
• Systems Software:     - Provides a platform for other software to run.     - Compilers: Translates High-Level Language (HLL like Python, Java, C++) into machine code. The original is source code; the output is object code.     - Linkers (Link Editor): Combines separate object files (modules) into a single program.     - Device Drivers: Enable hardware (printers, mice) to communicate with the Operating System (OS).     - Operating System (OS):         - Runs in the background and manages basic functions.         - Controls I/O operations, user communication, security (passwords), error handling, and program loading.     - Utilities: Software for specific maintenance tasks (Antivirus, Backup, Disk Defragmenter, File Management).

Analogue and Digital Data

• Analogue Data:     - Physical data that changes smoothly between values (infinite values).     - Found in the real world.
• Digital Data:     - Discrete exact values in binary form ($base\,2$ system: $1$ and $0$).     - Computers only understand binary.
• Conversion Devices:     - Analogue-to-Digital Converter (ADC): Used when sensors send data to a computer.     - Digital-to-Analogue Converter (DAC): Used when a computer controls an analogue device (e.g., a motor).

The Startup Process: BIOS and CMOS

• BIOS (Basic Input/Output System):     - Contained in ROM as a "boot file."     - Directs the computer upon startup: performs a hardware check and loads the OS into RAM.
• CMOS (Complementary Metal Oxide Semiconductor):     - A non-volatile, battery-powered chip.     - Stores the system date, time, and system configuration.

User Interfaces: CLI, GUI, and Emerging Types

• Command Line Interface (CLI):     - User types specific instructions from memory.     - Pros: Direct communication; unrestricted by pre-determined options.     - Cons: Slow, requires learning many commands.     - Users: Programmers, analysts, technicians.
• Graphical User Interface (GUI):     - Uses pictures/symbols (icons). Features WIMP (Windows, Icons, Menu, Pointing Device).     - Users: End-users who do not need technical knowledge.     - Post-WIMP: Refers to touch screens using gestures (pinching, rotating).
• Dialogue-Based Interface: Uses human voice (e.g., Siri, Alexa, luxury car navigation).
• Gesture-Based Interface: Relies on body movements (hand, head, foot) via sensors or cameras. Example: Foot sensor to open a car's boot.

Types of Computers and Their Specifications

• Desktop Computers:     - General-purpose; separate components (monitor, mouse, etc.).     - Advantages: Standardized spare parts, easier to upgrade, better specs for cost, stable wired internet.     - Disadvantages: Not portable, wire clutter.
• Laptops:     - Single unit; portable.     - Features: Low power consumption, low heat output, lightweight.
• Smartphones:     - Pocket-sized OS (iOS, Android). Features: cameras, sensors (accelerometers, proximity sensors), Bluetooth, Wi-Fi/5G connectivity.     - Emerging tech: OLED (Organic Light Emitting Diode) screens; LI-FI (using light for faster communication).
• Tablets:     - Touchscreen technology; no physical keyboard (virtual keyboard/stylus used).     - Phablet: A hybrid between a smartphone and a tablet.

Emerging Technologies: AI and Extended Reality

• Artificial Intelligence (AI):     - Machines performing tasks requiring human intelligence (facial recognition, language use, autonomous driving).     - Positive Impacts: Improved safety (driverless cars), robots for dangerous tasks (bomb disposal, nuclear disaster zones).     - Negative Impacts: Job losses in manufacturing/transport, loss of human skills.
• Extended Reality (XR):     - Augmented Reality (AR): Digital details overlaid on the physical world (Pokémon GO, Apple Vision Pro). Used in healthcare (surgery planning) and retail (virtual makeup).     - Virtual Reality (VR): Fully immersed in a simulated world via a 360-degree headset. Used in military training, education, and sports (golf swing improvement).

Input Devices: Detailed Mechanism and Use

• Keyboards: Membrane or circuit board base identifies key presses via a CPU index file. High risk of Repetitive Strain Injury (RSI).
• Pointing Devices:     - Optical Mouse: Detects movement using reflected light; no moving parts to clog.     - Trackpad: Tactile sensor on laptops.     - Trackerball: Ball on top; easier for those with limited wrist movement.
• Direct Data Entry / Automatic Data Collection:     - Magnetic Stripe Readers: Read account details on plastic cards; robust but affected by magnetic fields.     - Contactless Card Readers: Uses radio waves for transactions ($10\,seconds$ vs $30\,seconds$ for magnetic).     - Chip and PIN: Inserted into reader; requires PIN for higher security.     - RFID (Radio Frequency Identification):         - Components: Microchip + Antenna.         - Types: Passive (uses reader's energy) and Battery-powered.         - Uses: Livestock tracking, retail bulk detection (<100\,ms response).     - OMR (Optical Mark Recognition): Reads pencil marks on forms (exams, ballots). Fast but requires precise form design.     - OCR (Optical Character Recognition): Converts hard copies/number plates into electronic text.     - Barcode Readers: Scan dark and light lines. Used for stock control.     - QR Codes: Matrix of squares; holds up to $4296\,characters$ (vs $30$ for barcodes).
• Sensors: Measure physical quantities ($pH$, pressure, humidity). Always require an ADC to interface with computers.
• Specialized Input:     - Microphones: Sound vibrates a diaphragm $\rightarrow$ moves a coil $\rightarrow$ generates current $\rightarrow$ sound card converts to digital.     - Light Pens: Detect light changes on CRT monitors; used in CAD.

Output Devices: Display and Printing

• Monitors:     - CRT (Cathode Ray Tube): Heavy, high power consumption, heat hazard; used in CAD with light pens.     - LCD/LED: Thin Film Technology (TFT). LED backlighting provides immediate brightness and energy efficiency.     - OLED: Thinner screens that generate their own light without backlighting.
• Printers:     - Laser: High-speed, high-volume; uses charged drums and toner.     - Inkjet: Sprays ink droplets (thermal bubble or piezoelectric); high quality for single photos.     - Dot Matrix: Pins strike an inked ribbon. Used for carbon copies (multi-part stationery) in dirty environments.     - Graph Plotters: Use pens to draw continuous vector lines on large sheets (architectural diagrams).
• 3D Printers: Additive manufacturing. Creates objects layer-by-layer (<0.1\,mm thick). Applications: Prosthetics, aerospace parts, custom medical organs.
• Audio Output: DAC converts digital to current $\rightarrow$ Amplifier $\rightarrow$ Electromagnet moves a cone to produce sound waves.
• Actuators: Electromechanical devices (e.g., Solenoids) that translate digital signals into physical movement (valves, motors).

Storage Media and Backup

• Magnetic Storage:     - Magnetic Tape: Serial access; very slow access time but fast transfer rate. Used for long-term archiving.     - HDD: Rotating platters with read/write heads. Suffer from latency (rotation time).
• Optical Storage: Uses laser light to read pits and lands on polycarbonate disks.     - CD (Red laser: $780\,nm$).     - DVD (Red laser: $650\,nm$); allows dual-layering.     - Blu-ray (Blue laser: $405\,nm$); can store $5\times$ more data than DVD ($25\,GB$ to $50\,GB$).
• Solid-State Media: No moving parts; uses NAND flash memory. Floating gate and control gate transistors create bit values.     - SSD: Access time of $0.1\,ms$ (vs $10\,ms$ for HDD). SSD endurance is a limitation (finite write cycles).     - Memory Cards: SD, xD, CFast used in portable devices.

Networking and Communication

• Network Hardware:     - Hub: Sends data packets to all devices; low security, wastes bandwidth.     - Switch: "Intelligent hub" using MAC addresses and look-up tables to send data only to the recipient.     - Bridge: Connects two LANs using the same protocol.     - Router: Connects LANs to the internet using IP addresses; uses routing tables.
• Wireless Technologies:     - Bluetooth: Spread-spectrum frequency hopping (switching between $79$ channels in $2.4\,GHz$ band) for secure short-range connection (personal area networks).     - Wi-Fi: Full-scale network access ($2.4\,GHz$, $5\,GHz$, or $6\,GHz$); range up to $100\,m$.
• Cloud Storage:     - Public: (Google Drive, Dropbox).     - Private: (Dedicated bank servers behind firewalls).     - Hybrid: Mix of both for sensitive/non-sensitive data.
• Data Packets: Consist of a Header (sender/receiver IP, sequence number, packet size) and a Trailer (error-checking, end indicators).
• IP Addresses:     - IPv4: $32\,bits$ (e.g., $254.25.28.77$).     - IPv6: $128\,bits$ (e.g., $A8FB:7A88:FFF0:0FFF:3D21:2085:66FB:F0FA$).

Security and Data Protection

• Authentication Methods:     - Biometrics: Fingerprints, facial recognition, iris scans.     - Passwords: Strong passwords require capital letters, numbers, and symbols (e.g., Sy12@#TT90kj=0).     - Tokens: Physical devices that generate a One-Time Password (OTP) valid for <1\,minute.
• Threats:     - Hacking: Unauthorized access to a computer system.     - Phishing: Fake emails to get personal data.     - Pharming: Malicious code redirecting users to fake websites.     - Smishing/Vishing: Phishing via SMS or Voicemail.     - Malware:         - Viruses: Replicate and corrupt files; require a host program.         - Worms: Stand-alone; self-replicate across networks without user action.         - Trojan Horse: Disguised as legitimate software.         - Spyware/Keyloggers: Record keystrokes to steal passwords.         - Ransomware: Encrypts data and demands payment for the key.
• Software Protection:     - Anti-Virus: Uses Heuristic checking (analyzing behavior for new viruses) and quarantine databases.     - Firewalls: Sits between computer and network; filters traffic based on user criteria.
• Legal Standards:     - Data Protection Act (DPA): Principles include fair processing, accuracy, security, and not keeping data longer than necessary.

Systems Life Cycle

• Stage 1: Analysis: Methods include observation, interviews, questionnaires, and document examination. Analyst produces a Data Flow Diagram (DFD).
• Stage 2: Design: Planning file structures, input/output formats, and validation routines (Range, Type, Length, Format, Presence, Check Digit).
• Stage 3: Development and Testing:     - Normal Data: Acceptable values.     - Extreme Data: Values at the boundaries of acceptability.     - Abnormal Data: Invalid values that should be rejected.
• Stage 4: Implementation:     - Direct Changeover: Stop old, start new immediately.     - Parallel Running: Both systems run side-by-side.     - Pilot Running: New system used in one branch first.     - Phased Implementation: Parts of the system introduced one at a time.
• Stage 5: Documentation: Technical (for programmers) and User (for the public).
• Stage 6: Evaluation: Comparing the solution to original requirements.

ICT Applications in Society

• Medicine:     - 3D Bio-printing: Using bio-inks for artificial cells/tissues.     - Printlets: 3D printed tablets for optimized medicine release.     - CAD/CAM: 3D models of organs for pre-surgical planning.
• Banking:     - EFT (Electronic Funds Transfer): Moving money without physical cash.     - ATM Processing: OCR reads deposited cheques; account updated after $24\u201348\,hours$.
• Manufacturing: Robotics for paint spraying and welding. Programmed via humans wearing sensors on their arms to record position and rotation.
• Transport:     - Autonomous Vehicles: Rely on LiDaR (Light Detection and Ranging) for 3D mapping.     - ANPR: Uses OCR to read number plates for car park barriers or average speed monitoring.
• Education:     - Computer-Aided Learning (CAL): Multimedia and micro-learning modules.     - Biometric Attendance: Higher security than magnetic cards.
• Modelling: Using mathematical representations to predict behavior (Personal finance, Weather forecasting, Bridge design).