CAIE IGCSE ICT (0417) Exhaustive Theory Study Notes
Types and Components of Computer Systems
Hardware: The electronic, physical components that make up a typical computer system, including input and output devices. * Internal Hardware Devices: * Central Processing Unit (CPU) / Processor * Motherboard * Internal memory: RAM and ROM * Graphics and Sound Cards * Internal Storage: Hard Disk Drives (HDD) and Solid-State Drives (SSD) * Network Interface Card (NIC) * External Hardware Devices: * Monitor * Keyboard * Mouse * Printer * External Storage Devices
Software: The techniques, methods, commands, and instructions that tell the device what to do and how to do it. These are programs that control the system and process data. * Application Software: Provides services for specific tasks. Can be general-purpose or custom-made (specialist software). * Examples: Spreadsheets, databases, and word processors. * System Software: Designed to provide a platform for other applications to run. * Compilers: Translates High-level language into Machine code (Language Processor). * Linkers: Creates links between language processors into workable solutions (Data definition language). * Device Drivers: Enables a device to work with an externally connected device. * Utilities: Provides necessary facilities such as Antivirus, Scan Disk, and Disk Defragmentation. * Operating Systems (OS): Developed to enable systems to function and allow user communication.
Analogue and Digital Data: * Computers understand binary digits ( and ), known as digital data. * Real-world data is analogue and not limited to specific values. * Analogue data forms smooth curves; digital data changes in discrete steps. * Conversion Hardware: * ADC (Analogue to Digital Converter): Converts received real-world data into digital form for processing. * DAC (Digital to Analogue Converter): Converts digital output back into analogue form.
The Main Components of Computer Systems
Central Processing Unit (CPU): * Also known as a microprocessor; a single integrated circuit core for PCs and control/monitoring in gadgets. * Components: * Control Unit (CU): Manages input and output devices. * Arithmetic and Logic Unit (ALU): Performs computations and logical judgments. * Registers: Tiny memory regions for processing.
Internal Memory: * Random Access Memory (RAM): * Temporary/volatile memory lost when power is shut down. * Performs read and write functions. * Stores data currently in use. * Can be increased to improve operational speed. * Read-Only Memory (ROM): * Permanent/non-volatile memory that can only be read from. * Stores configuration data like the BIOS. * BIOS (Basic Input/Output System): Stores date, time, and system configuration on a CMOS (Complementary Metal Oxide Semiconductor) chip, usually battery powered.
Differences Between Internal Memory and Backing Storage: * RAM is volatile; ROM is permanent; Backing storage is permanent without power. * RAM/ROM are much smaller than backing storage. * RAM/ROM are significantly faster in accessing data than backing storage. * Backing storage is much cheaper than internal memory. * Internal memories are fixed; backing storage can be fixed or portable. * CPU reads internal memory directly; backing storage must be moved to RAM first.
Operating Systems and Interface Types
Functions of an Operating System: * Controls operations of input, output, and backing storage. * Supervises loading, running, and storage of application programs. * Deals with application errors and maintains security. * Maintains a computer log.
User Interface Types: * Command Line Interface (CLI): * User types commands; used mainly by programmers for direct communication. * High flexibility for configuration but requires learning many commands. * Time-consuming and error-prone due to fixed formats/spellings. * Graphical User Interface (GUI): * Uses WIMP (Windows, Icons, Menus, Pointing device). * User-friendly for end-users without deep technical knowledge. * Uses more memory than CLI and restricts users to provided icons. * Dialogue-Based Interface: * Uses human voice for commands; useful for drivers and people with disabilities. * Can be used as a security feature via voice recognition. * Often unreliable due to background noise or complex setup. * Gesture-Based Interface: * Relies on moving hands, head, or feet; no physical contact required. * Natural interface with no training needed. * Risks picking up unintentional movements; limited range (maximum of ).
Types of Computers
Desktop Computers: * General-purpose unit with separate monitor, keyboard, mouse, and processor. * Advantages: Easier/cheaper to upgrade, stable internet via wired connections, no power consumption limits. * Disadvantages: Not portable, clutters desk space with wiring, requires copying files to move work.
Laptop Computers (Notebooks): * Monitor, keyboard, pointing device, and processor are combined in one portable unit. * Characteristics: Lightweight, low power consumption, low heat output. * Advantages: Portability, no trailing wires, takes up less space. * Disadvantages: Easier to steal, limited battery life, keyboards/trackpads can be awkward to use.
Smartphones: * Use OS (iOS, Android, Windows) to run apps/applets. * Communicate via Wi-Fi hotspots or , , and networks. * Advantages: Very small and lightweight, instant location tracking via apps, reasonable battery life. * Disadvantages: Small screens/keyboards make reading difficult, battery drains quickly with web use, less memory than laptops.
Tablets: * Similar to smartphones but larger. * Advantages over laptops: Very fast startup, touch screen technology, longer battery life. * Disadvantages over laptops: Expensive, limited storage, typing on glass is prone to errors.
Phablets: * Hybrid between a tablet and smartphone; screens are larger than smartphones but smaller than tablets.
Emerging Technologies
Artificial Intelligence (AI): * Machines carrying out tasks requiring intelligence, such as language recognition and data prediction (weather forecasting). * Isaac Asimov's Three Laws of Robotics: 1. Robots may not injure a human through action or inaction. 2. Robots must obey human orders unless conflicting with the first law. 3. Robots must protect themselves unless conflicting with the first two laws. * Everyday Uses: Autonomous (driverless) vehicles, robotic prosthetics for amputees, bomb disposal. * Negative Impacts: Unemployment, technological dependency, and de-skilling of human talent.
Extended Reality (XR): * Augmented Reality (AR): Merger where virtual objects are laid onto real-world objects (e.g., Pokémon GO!). * Virtual Reality (VR): Creates an entirely new world requiring hardware like headsets, joysticks, and headphones.
Input Devices and Their Uses
Keyboards: Used for typing text and commands. Faster for text entry but can cause RSI and take up desk space.
Numeric Keypads: Used in ATMs, mobile phones, POS terminals, and Chip and PIN devices. Faster for numeric data than standard keyboards.
Mouse: Used for navigating GUIs and image editing. Quicker than keyboards for selection but requires a flat surface.
Touchpad: Integrated into laptops to aid portability. No separate surface needed, though drag-and-drop can be complex.
Tracker Ball: Robust alternative to a mouse; used in industrial control rooms or for people with RSI. Needs less space.
Remote Control: Operates devices from a distance (TVs, industrial hazardous environments). Signal can be blocked by obstacles.
Joysticks: Used for video games and simulators to mimic controls; pointer control on-screen is more difficult.
Driving Wheel: Realistic vehicle experience for racing games and simulators; steering can be over-sensitive.
Touch Screen (Input): Used in ATMs, restaurants (POS), and interactive whiteboards. Fast entry but screens get dirty and frequent use strains muscles.
Scanners: Converts documents/photos into digital formats. Used with OCR for fast text entry. Resolution limits quality.
Digital Cameras: Better quality than many mobile devices; used in dentistry and VR tours. Saves money on film.
Microphones: Used for speech input, voice recognition authentication, and VoIP. Sound files consume large memory.
Sensors: Capture physical data for computers (analogue signals requiring ADC). * Temperature: Washing machines, glasshouses. * Pressure: Intruder alarms. * Light: Street lighting, automatic doors. * Sound/Acoustic: Monitoring powder flow in pipes, alarms. * Humidity/Moisture: Environmental monitoring, factories. * pH: Chemical processes, environmental monitoring.
Light Pens: Used for selecting objects or drawing on CRT screens; higher accuracy than touch screens but outdated.
Direct Data Entry Devices
Magnetic Stripe Readers: Reads cards at ATMs or security entries. Fast and robust, but data is lost if the card is damaged.
Chip and PIN Reader: More secure than contactless as it requires a PIN; robust system.
Contactless Card Reader: Faster transactions and encryption to prevent sniffing, but has transfer limits and potential for thieves to monitor signals with suitable readers.
RFID Readers: Uses radio waves for livestock tracking, retail, and library books. No line-of-sight required and bulk detection possible, but prone to tag collision and hacking/jamming.
Optical Mark Reader (OMR): Checks MCQ papers and voting forms. Fast and accurate without human intervention; requires precise form design.
Optical Character Recognition (OCR): Processes IDs and digitizes historic copies. Much faster than manual typing but struggles with handwriting.
Barcode Readers: Used for stock control. Trusted technology but barcodes can be swapped or damaged.
Quick Response (QR) Code Scanner: Holds more info than barcodes and is easier to read with smartphone cameras. Can be encrypted but can transmit malicious data.
Output Devices and Their Uses
CRT Monitors: Large screens for CAD and light pens. Bulky, run hot, and flickering can cause headaches.
LCD Screens: Modern standard for mobile devices. Highly efficient and sharp but contrast varies by angle; motion blur can occur.
Multimedia Projectors: Used for training/advertising. Allows large crowds to view, but images can be fuzzy and setup is complex.
Laser Printers: High-speed, high-volume, high-quality. Toner lasts long but produces ozone and volatile organic compounds.
Inkjet Printers: Cheaper initial cost, lightweight, and produce no ozone. Slow for large jobs; ink can smudge.
Dot Matrix Printers: Used for carbon copies (till receipts) and continuous printing. Very noisy and poor quality but cheap to maintain.
Plotters: Produces high-quality architectural/engineering drawings on a large physical footprint.
3D Printers: Creation of prosthetic limbs, aerospace parts, and vintage car parts. Risk of counterfeit or dangerous item manufacture.
Speakers: Amplifies sound for crowds or visually impaired people; takes up desk space and can disturb others.
Actuators: Used to turn on motors, buzzers, and switches to control physical devices. Analogue devices requiring DAC.
Storage Devices and Media
Backing Up Data: Copying files to a different medium to safeguard against loss, hackers, or format damage.
Magnetic Storage Media: * Magnetic Tape: Huge capacity for batch processing and long-term archiving. Uses serial access (slow). * Fixed Hard Disk (HDD): Primary storage for OS and files. Fast data transfer but has noisy moving parts prone to damage. * Portable HDD: Fast transfer for backups between computers; easily damaged if dropped.
Optical Media: * CD-R / DVD-R: Write once only; behave like ROM once finalized. * CD-RW / DVD-RW: Recordable and erasable; used in CCTV and television recordings. * CD-ROM () / DVD-ROM (): Read-only memory for software and films. * Blu-Ray: Uses a blue laser ( wavelength) compared to DVD's red laser (). Larger pits allow more data. Transfer rate: (vs DVD's ).
Solid State Storage: * SSD: No moving parts, thinner, cooler, and faster access times ( vs HDD ). Limited endurance (rated at write per day for years). * Flash Memory Cards: SD, XD, and CFast cards used in cameras/phones. Compact but easily lost or stolen.
Networks and Communication
Network Addressing: * IP Address: Unique number on a network. IPv4 is -bit; IPv6 is -bit. * MAC Address: Unique identifier for a NIC. First six hex digits are manufacturer code; second six are serial number.
Hardware Devices: * Routers: Send data between different network types; consult routing tables to route data packets. * HUBS: Connect devices in a LAN; broadcast data to all ports (insecure/excess traffic). * Switches: Intelligent hubs; use a lookup table of MAC addresses to send data only to the relevant device. * Bridges: Connect two LANs using the same protocol; scan MAC addresses.
Wi-Fi vs. Bluetooth: * Bluetooth: Uses ; intended for close-range, low-bandwidth, up to devices. * Wi-Fi: Uses ; higher range, faster transfer, uses WPA/WEP encryption.
Cloud Computing: * Public: Third-party provider. * Private: Owned by the single organization. * Hybrid: Sensitivity-based selection between public and private.
Network Types: * LAN: Single building; uses hubs/switches. * WLAN: Network without physical cables; uses WAPs but signal is affected by walls. * WAN: Connects geographically dispersed LANs using routers and modems; expensive and subject to external provider reliability.
Information Environments: * Internet: Open global network; WWW is a collection of pages on it. * Intranet: Private organizational network behind a firewall. * Extranet: Intranet allowing restricted access to selected external parties (stakeholders/clients).
Network Issues and Authentication
Threats: Hacking (unauthorized access), Phishing (malicious emails), Pharming (code redirecting to fake websites), Viruses (self-replicating code).
Passwords: Should be changed regularly and contain uppercase, lowercase, numbers, and symbols (e.g., 1lov3ICT# vs ).
Other Authentication: * Zero Login: Biometric/seamless access without passwords. * Physical/Electronic Tokens: Objects or apps creating One-Time Passwords (OTP). * Smart Cards: Integrated circuits for banking/secure transactions.
Anti-malware: Detects, prevents, and removes threats. Uses databases and Heuristic Checking (behavioral patterns).
Electronic Conferencing
Video Conferencing: Real-time audio/video using webcams and CODECs (coder-decoder). Reduced travel costs but prone to time lag and expensive setup.
Audio Conferencing: Meetings using telephone networks/internet phones; lacks visual engagement.
Web Conferencing (Webinars): Uses internet for screen sharing and interactive features like polling and Q&A.
Effects of Using IT
Microprocessor-Controlled Devices: Labor-saving (smart fridges, automated alarms). Can lead to lazy lifestyles and cybersecurity breaches.
Social Interactions: VoIP makes staying in touch cheaper, but lack of face-to-face contact causes social isolation and anxiety.
Transport Systems: * Monitoring: ANPR (Number plate recognition) for traffic fines and spotting car thefts. * Autonomous Vehicles: Uses sensors, cameras, and actuators. Safer without human error but high cost and hacking fears. * Autonomous Trains/Planes: Improved punctuality and safety but requires continuous CCTV and software glitch protection.
Health Problems: * RSI: Repetitive wrist movements. Prevention: Ergonomic equipment. * Back/Neck Strain: Poor posture. Prevention: Adjustable chairs. * Eyestrain: Prolonged screen use. Prevention: Anti-glare screens, regular breaks. * Ozone Irritation: From laser printers. Prevention: Ventilation.
ICT Applications in Communication
Newsletters: Targeted deep relationship building; time-consuming.
Posters: Quick visual advertising; limited space.
Websites: Worldwide advertising with hyperlinks and hit counters.
Multimedia Presentations: Mixture of media for audiences; high feature density can distract.
Media Streaming: Real-time transition using buffering to ensure smooth playback without freezing.
ePublications: Digital books/magazines; lack tactile feel and can cause eyestrain.
Modelling and Computer-Controlled Systems
Modelling Applications: Personal finance, bridge design, flood management, traffic management, and weather forecasting. Safer and faster than real-life trials ( monitoring).
Robotics in Manufacturing: Assembly and welding. Pros: Work non-stop in harmful environments. Cons: High setup cost and job loss.
School Management: Attendance via magnetic cards or biometrics. Performance tracking via spreadsheets. * Biometrics vs Cards: Fingerprints prevent attendance forgery but are an invasion of privacy.
Banking Applications: * ATM Sequence: Card insertion -> PIN check -> Account check -> Funds dispense -> Account update. * EFT: Electronic Money transfer between accounts; no cash moved. * Internet Banking: Convenient for bill payments but higher fraud risk.
Expert Systems: Emulates human decision-making via AI. Components: * User Interface: Interaction layer. * Explanation System: Reasoning/Suggested actions. * Inference Engine: Search engine examining knowledge base using rule base. * Knowledge Base: Repository of facts. * Rules Base: Inference rules.
Recognition and Satellite Systems
Retail Technology: * POS Terminals: Checkout counters managing sales/stock. * EFTPOS: Processing secure electronic payments via chip and PIN or NFC (Near Field Communication).
ANPR: Sensors trigger cameras -> Algorithm isolates plate -> Characters segmented and recognized via OCR -> Stored in database.
RFID in Passports: Gate opens automatically if face recognition matches RFID chip image.
Satellite Systems: * GPS (Global Positioning System): Uses at least three satellites with atomic clocks to calculate exact position on Earth. * GIS (Geographic Information Systems): Analyzes geographically referenced data (e.g., nearest petrol station). * Media Communication: Uses satellites for remote reporting; high bandwidth but weather-affected.
The System's Life Cycle
Analysis: Observation (first-hand), Interviews (depth), Questionnaires (quantifiable), Examination of documents.
Design: Field names, data types, validation routines, and input/output formats.
Development and Testing: Identification of errors using Test Plan. * Data Types: Normal (expected), Abnormal (invalid/wrong type), Extreme (limits of acceptability), Live (previously used data).
Implementation: * Direct Changeover: Fast but high risk. * Parallel Running: Comparison possible but resource-intensive. * Pilot Running: Trial in one department/group; low risk. * Phased Implementation: Stages; gradual transition.
Documentation: * Technical: Code, algorithms, hardware requirements for developers. * User: How to install, run, and troubleshoot for end-users.
Evaluation: Assess efficiency (time/money), ease of use (minimal training), and suitability (matching requirements).
Safety and Security
Physical Safety: * Electrocution: Spilling liquids, overloaded sockets. Prevention: Circuit breakers/fuses. * Fire: Overheated equipment. Prevention: Ventilation, fire extinguishers. * Trailing Cables: Trip hazards. Prevention: Cable ties. * Falling Equipment: Unstable surfaces. Prevention: PCs on solid desks away from edges.
eSafety (DPA/GDPR): Personal data must be accurate, secure, processed lawfully, and not kept longer than necessary.
Data Threats & Prevention: * Smishing/Vishing: Phishing via SMS or voice. * Trojan Horse: Disguised as legitimate software. * Worms: Standalone malware spreading through networks. * Shoulder Surfing: Illegally observing screens.
Protection Methods: * Encryption: Scrambling data into unreadable format without a key. * SSL (Secure Socket Layer): Protocol creating secure connection; indicated by HTTPS. * 2FA (Two-Factor Authentication): Combining multiple identification factors.
Copyright: EULA (End-User License Agreement) and DRM (Digital Rights Management) prevent software piracy.
Communication with Other Users
Email etiquette (Netiquette): Be clear, avoid CAPITAL LETTERS (shouting), don't spam, forgive mistakes.
Employer Guidelines: Rules on email duration, viruses, and confidentiality.
Carbon Copies (Cc vs Bcc): Cc for transparency; Bcc for concealing recipient list.
Search Engines: Refining searches using specific terms (+\/-\,"").
Internet Protocols: * HTTP/HTTPS: Communication rules. * FTP (File Transfer Protocol): Specifically for file transfers. * SSL: Secure data reception.
Social/Collaborative Tools: * Blogs: Chronological opinion/insight sharing. * Forums: Peer-to-peer discussion threads; can be moderated. * Wikis: Collaborative knowledge sharing (e.g., Wikipedia). * Social Networking: Profile-based content sharing (Facebook, LinkedIn).