Edexcel IGCSE ICT Revision Notes: Digital Devices, Peripherals, and Storage

Digital Device Classifications and Types

  • Mainframe Computer: This is a large and powerful computer designed to execute complex tasks, such as high-level statistical analysis, at high speeds. A defining feature of mainframes is that they can be used by many people simultaneously.

  • Microprocessor: This component controls computer operations. Its workflow consists of three stages: taking data as input, processing that data, and producing an output. They are found in various household appliances including:

    • Washing machines.

    • Televisions.

  • Personal Computers (PCs): This category includes laptops and desktops. Laptops are versatile and can serve as desktop replacements.

  • Single Board Computers: These are affordable computing systems used primarily in three specialized areas:

    • 1) Education: Used for learning and teaching ICT principles.

    • 2) Embedded Computing: Hardware that is fixed in a specific position to carry out a specialist task. A common example is a calculator.

    • 3) Physical Computing: Interactive systems that detect and respond to their surrounding environment. A common example is robotics.

    • Distinction: Embedded computing and Physical computing are described as "total opposites."

  • Mobile Connectivity and SIM Cards: Mobile phones require a SIM card to connect to a network.

    • SIM: Stands for Subscriber Identity Number. Its purpose is to identify the specific device on the mobile phone network.

  • Specialist Phones: These are devices designed with specific features to meet user needs, such as an "accessibility need" or an "Emergency feature."

  • Smartphones: These devices offer standard mobile phone features plus Wi-Fi connectivity and internet access.

    • They integrate features typically found in other devices, such as cameras and handheld game consoles.

    • They utilize complex operating systems that consume high amounts of energy, requiring more frequent charging compared to other mobile phones.

  • Tablets: These are slightly larger than smartphones but generally perform the same functions.

  • Navigation Aids: Devices that calculate optimal routes based on the shortest distance, least traffic, and shortest travel duration. They rely on two distinct systems:

    • GPS (Global Positioning System): Utilizes multiple satellites crossing radio signals to pinpoint location. It does not require an internet connection.

    • GIS (Geographical Information System): Used to render the visual elements of maps, such as roads and houses. This system requires an internet connection.

  • Wi-Fi: A method of connecting machines or computers to a network or the internet using radio signals.

Peripheral Devices: Input

  • Definition: A peripheral device is any device connected to a computer to provide input, output, or storage capabilities.

  • Keyboards: Standard input devices for text.

  • Pointer Devices: Includes the Mouse, Tracker ball, Track Pad, Joystick, and Graphics tablet.

  • Scanners:

    • OCR (Optical Character Recognition): Used to scan text and numbers.

    • OMR (Optical Mark Recognition): Used to scan marks, typically on multiple-choice (MCQ) exam papers.

  • Barcode Scanners:

    • Linear: Found on food products and standard retail items.

    • Matrix (QR): These hold more information than linear barcodes and can be scanned from any angle.

  • Webcams: Used for video input.

  • Microphones:

    • Mechanism: Air hits a diaphragm, causing it to move.

    • Signal Path: This movement produces an analogue electrical signal, which is then converted into a digital signal using the computer's sound card.

  • Touch Screens:

    • Resistive: Functions when physical force is applied by fingers.

    • Capacitive: Functions via the transfer of electrical signals from fingers to the screen.

  • Biometric Scanners: Used for security and identification. Types include Iris, Fingerprint, Face, and Voice.

    • Fingerprints: Classified into types including Arches, Loops, and Whorls.

    • Iris: Noted as the most secure biometric method.

    • Advantages: Easier to use, harder to trick, enables faster transactions, and has no language barriers.

    • Disadvantages: Must store personal information, expensive to implement, and may make some users feel uncomfortable.

  • Card Readers:

    • Magnetic Strip: The least secure type because no PIN is required for the transaction.

    • Programmable Chip: The most secure type because data is only readable once the correct PIN is entered.

    • RFID and NFC (Radio Frequency Identification and Near Field Communication): Used for contactless payments like Apple Pay. When scanned, an ID is linked to database records through wireless communication.

  • Sensors: Devices that input data from the physical environment.

    • Benefits: Can be placed in dangerous locations, provide continual monitoring, remove human error, and produce data that is easily analyzed.

Peripheral Devices: Output and Control

  • Monitors: Quality is determined by screen size, resolution, and energy efficiency.

  • Printers:

    • Dot Matrix: Operates by punching holes through paper. It is very loud and very slow, but offers the cheapest cost per copy and can perform carbon printing.

    • Inkjet: Uses a motor to move a printer head across the page, spraying ink through nozzles from cartridges. It is quick and high-quality but expensive per copy.

    • Laser: Utilizes a drum to emit an electrical charge (functioning similarly to a physics photocopier). It is the fastest and has the highest initial cost, with a medium cost per copy and the highest output quality.

    • 3D Printers: Create physical, real-life versions of digital models.

  • Plotters: Specialized output devices used by cartographers for map drawing.

  • Data Projectors: Quality is dependent on zoom functionality, lens quality, light bulbs, and resolution.

  • Speakers:

    • Mono sound: Produced from one side/source.

    • Stereo sound: Produced from two different sides.

    • Surround sound: Produced from all different sides.

  • Control Devices: These are system components that initiate real-life actions or movements.

Home Entertainment and Multi-functional Systems

  • Game Consoles: Enable video game play on television screens. Features include motion sensors, wireless controllers, and virtual reality (VR) controllers.

    • Handheld Consoles: Typically have less storage, resulting in lower quality games compared to home systems.

  • Home Entertainment Systems: Comprehensive setups including Televisions, Sound Systems, PVRs, and Blu-Ray/DVD players.

    • Televisions: Quality depends on resolution (HD/UHD). Notably, manufacturers only present the count of vertical pixels. Smart TVs include apps and internet connectivity.

    • PVR (Personal Video Recorder): A device that records broadcasted content for later viewing.

    • Set-top box: A device that receives audio and video from a broadcaster and sends it to the television.

    • Compatibility: A DVD player cannot play Blu-Ray discs, but a Blu-Ray player can play DVDs.

  • Media Players: Devices like Apple TV or Google Chromecast that connect to a TV. Content can originate from the internet or a locally stored network. Portable versions are compact and utilize flash memory.

  • Multifunctional Devices: Devices capable of performing various functions (e.g., a phone that takes photos, sends messages, and acts as a console).

    • Convergence: The process where device designs change so they become similar to one another. An example is a laptop that flips to form a tablet.

Device Features and Performance

  • Portability: The ease with which a device can be carried and moved.

  • Performance: Defined by processing speed. High speed requires a good processor and a large RAM.

    • Virtual Memory: Storage used by the processor as a temporary measure once RAM space has run out. This results in significantly slower task execution.

  • Storage: Higher storage allows for more files and programs. It also affects performance via its role in virtual memory.

  • User Interface (UI): Methods for user-system interaction:

    • Command Line: Typing commands (complex and inefficient).

    • Menu-Driven: Choosing from a list (e.g., ATMs); might not offer the exact desired option.

    • Graphical User Interface (GUI): Uses windows, icons, and menus; very effective but requires high storage.

    • Voice Driven: e.g., Siri.

    • Gesture Interface: Using swipes and finger movements.

  • Connectivity: Ability to share data wirelessly or via cables.

  • Media Support: Capability to read/write items like memory cards; some devices require external readers.

  • Energy Consumption: Low consumption leads to longer battery life, saving money and presenting social responsibility.

  • Expansion Capability: Some PCs allow installation of additional components through dedicated expansion slots.

  • Security Features:

    • Software Security: Includes PINs, Passwords, Swipes, Patterns, and Biometrics. Complexity and randomness improve security.

    • Physical Security: Specialized slots and physical locks.

Storage Media and Data Representation

  • Medium vs. Device: The "Medium" (e.g., a DVD disk) is what holds the data. The "Device" (e.g., a DVD drive) is what reads the data.

  • Secondary Storage: Non-volatile storage (data is not lost during power loss). Uses include storing documents/files, storing applications for loading into RAM, and Virtual Memory.

  • Hard Disk Drives (HDD): Contains concentric platters and a spindle with a read/write head.

    • Speed factors: Revolutions Per Minute (RPM) of platters and the speed of the read/write head movement.

    • Mechanism: Reading transforms a magnetic field into electric current; Writing transforms electric current into a magnetic field.

    • Seek Time: The time taken by the Read/Write head to locate the specific area on the platter.

  • Optical Media:

    • CDs: 700 MB700\,\text{MB}; Laser writes on plastic beneath aluminum and acrylic layers.

    • DVDs: 4.5 GB4.5\,\text{GB} (One Sided) to 18 GB18\,\text{GB} (Two Sided). Uses a shorter wavelength red laser to store more data.

    • Blu-Ray: 25 GB25\,\text{GB} (One Sided) to 50 GB50\,\text{GB} (Two Sided). Uses an even shorter wavelength violet laser and includes scratch protection.

    • Notation: R = Recordable; W = Writable; RE = Writable, erasable, and re-writable.

  • Flash Media: No moving parts, energy-efficient, and portable.

  • Magnetic Tape: Historically for music, now used for both music and data.

  • Binary Storage Methods: All storage utilizes bits (00 or 11).

    • Hard Disk: Localized positive/negative charges on the platter.

    • Optical: Tiny bumps on the surface. Laser light reflects (11) or scatters (00).

    • Flash: Different levels of charge within individual tiny cells.

    • Magnetic Tape: Positive/negative charges on the tape surface.

Calculations and Accessibility

  • Data Measurements:

    • 8 bits=1 byte8\,\text{bits} = 1\,\text{byte}

    • 1 KiB=1024 bytes1\,\text{KiB} = 1024\,\text{bytes}

  • Storage Calculation Example: To construct an expression for the number of bits in 128 GiB128\,\text{GiB}, given that 1 KiB=10241\,\text{KiB} = 1024 and 1 GiB=102431\,\text{GiB} = 1024^3:

    • Total Bits=128×8×10243\text{Total Bits} = 128 \times 8 \times 1024^3

  • Accessibility Devices:

    • Braille Keyboards: Designed for users with visual impairments.

    • Gesture Interface: Designed for users with low mobility issues.