ICT Grade 8 Notes

Types of Digital Devices

  • Mainframe Computers
    • Large, powerful multi-user machines.
    • Execute complex tasks (e.g.
      statistical analysis) at high speed.
    • Simultaneous access for many users.
  • Microprocessors
    • Single integrated circuits that control a device’s logic.
    • Workflow: input ➜ processing ➜ output.
    • Embedded in everyday appliances (washing machines, TVs, etc.).
  • Single-Board Computers (SBCs)
    • Full computer on one small PCB.
    • Low-cost; popular in education, embedded systems & physical computing.
  • Embedded Computing
    • Fixed-function hardware & software sealed into a product.
    • Performs a dedicated task (e.g. engine control unit, smart thermostat).
  • Physical Computing
    • Interactive systems that sense & respond to the surrounding environment (motion, light, temperature, etc.).
Other Category Devices & Purposes
  • Mobile phone (requires a SIM = “Subscriber Identity Module”).
  • Digital camera — still photos; uses light sensors, lens quality & image processor define output quality.
  • Camcorder — video capture.
  • Game console — TV-based gaming; motion sensors, wireless/VR controllers; low-end handhelds use flash storage → lower game quality.
  • Home-entertainment systems
    • TVs (HD/UHD), sound bars, Blu-ray/DVD players.
    • PVR (Personal Video Recorder) records broadcast for later viewing; set-top boxes decode broadcasts.
  • Media player (streaming/locally stored content) — can be standalone or portable (flash memory).
  • Navigation aids — GPS + GIS for best route, traffic and ETA.
    • GPS\text{GPS}: satellite trilateration; no internet needed.
    • GIS\text{GIS}: renders maps, roads → requires data connection.

Resolution & Image Quality

  • Definition: number of pixels used to display an image.
  • Camera megapixel → max display size before pixelation:
    • 1−3  MP⇒1280×9601{-}3\;\text{MP}\Rightarrow1280\times960
    • 2  MP⇒1600×12002\;\text{MP}\Rightarrow1600\times1200
    • 3  MP⇒2048×15363\;\text{MP}\Rightarrow2048\times1536
    • 4  MP⇒2272×17044\;\text{MP}\Rightarrow2272\times1704
    • 5  +  MP⇒2560×19205\;+\;\text{MP}\Rightarrow2560\times1920
  • Pixelation = visible blocky pixels ⇒ unclear image.
  • TV resolution is stated horizontal×vertical\text{horizontal}\times\text{vertical} (e.g. 1280×9601280\times960).
  • Common display tiers
    • 8K UHD=7680×43208\text{K UHD}=7680\times4320
    • 4K DCI=4096×21604\text{K DCI}=4096\times2160
    • 2K DCI=2048×10802\text{K DCI}=2048\times1080
    • 1080p=1920×10801080p=1920\times1080

Device Design Trends & Features

  • Convergence
    • Devices evolve toward similar multi-function forms (phone = camera + console + messenger; laptops fold into tablets).
  • Key Features
    1. Portability — ease of transport.
    2. Performance — high clock speed & large RAM → fast processing.
    3. Virtual Memory — secondary storage used when RAM full; slows execution.
    4. Storage Capacity — more files/programs; affects VM performance.
    5. User Interfaces
    • CLI, menu-driven, GUI, voice, gesture.
    1. Connectivity — wired/wireless data sharing.
    2. Media Support — built-in readers vs external.
    3. Energy Consumption — low draw = longer battery, lower cost, social responsibility.
    4. Expansion Capability — internal slots for extra components.
    5. Security — software (PIN, password, biometrics) & physical (locks, Kensington slots).

Storage Technologies

Terminology
  • Storage medium: the physical object holding data (e.g.
    DVD disc).
  • Storage device: hardware that reads/writes the medium (e.g.
    DVD drive).
  • Secondary storage: non-volatile; retains data without power.
Hard Disk Drive (HDD)
  • Concentric magnetic platters spun by motor.
  • Speed factors
    1. RPM (revolutions per minute).
    2. Actuator seek time (head movement latency).
  • Read = magnetic ➜ electrical; Write = electrical ➜ magnetic.
  • Seek time = time to locate required track/sector.
Optical Media
MediumCapacityLaser Wavelength
CD700 MB700\,\text{MB}Red 780 nm
DVD (single)4.7 GB4.7\,\text{GB}Shorter red 650 nm
DVD (dual-side)≈18 GB\approx18\,\text{GB}
Blu-ray (single)25 GB25\,\text{GB}Violet 405 nm
Blu-ray (dual)50 GB50\,\text{GB}
  • Variants: R (recordable once) & RE/RW (rewritable).
Flash Media
  • Solid-state; no moving parts → portable, low-power.
  • Stores data as differing charge levels in cells (EEPROM technology).
Magnetic Tape
  • Sequential access; high capacity, low cost (modern backup archives).
Data Representation & Units
  • All media store binary 0/10/1.
  • HDD: polarity change.
  • Optical: pits & lands reflect laser.
  • Flash: cell charge level.
  • Conversions
    • 8  bits=1  byte8\;\text{bits}=1\;\text{byte}
    • 4  bits=1  nibble4\;\text{bits}=1\;\text{nibble}

Peripheral Devices

Input
  • Keyboard; pointing (mouse, trackball, track-pad, joystick, graphics tablet).
  • Scanner technologies