Edexcel IGCSE ICT - Digital Devices: Quick Review

1.1 Types of Digital Devices

Mainframe computer: Large, powerful, supports many users and complex tasks.
Microprocessor: Core control unit; input -> processing -> output.
Personal computers: Laptops and desktops; laptops as desktop replacements.
Single Board Computers: Affordable, used in Education, Embedded Computing, Physical Computing.
Embedded computing: Fixed in position; specialized task.
Physical computing: Interactive systems that respond to the environment.
SIM card: Subscriber Identity Module; identifies the device on the mobile network.
Specialist phones: Phones with features for accessibility or emergency needs.
Smartphones: Have Wi‑Fi and internet access; include features from other devices (camera, handheld games); more complex OS and higher energy use.
Tablets: Similar to smartphones but larger; usually similar function set.
Wi‑Fi: Wireless network connection method.
Navigation aids: GPS requires no internet; GIS requires internet to render maps and data.
Convergence (multifunction devices): Designs converge so one device performs multiple functions (e.g., phones with cameras, messaging, gaming).
Examples of convergence: Laptops that convert to tablets; multifunction devices.

Portability: Easy to carry.
Performance: High speed via good processors and RAM; virtual memory may be used if RAM is full.
Storage: More storage enables more data; storage can affect performance.
User interface types:
- Command Line
- Menu-Driven
- Graphical User Interface (GUI)
- Voice-Driven
- Gesture Interface
Connectivity: Data sharing via wireless or wired connections.
Media Support: Read/write from memory cards and similar media.
Energy Consumption: Lower energy = longer battery life, cost savings, and reduced environmental impact.
Expansion Capability: Some PCs allow adding components via expansion slots.
Security Features:
- Software security: PIN/password, swipe/patterns, biometrics.
- Physical security: Specialist slots/locks.

Multifunctional devices: One device performing multiple tasks (e.g., phone that takes photos, messages, calls, and games).
Convergence: Design trend where devices become similar to others in function.

Storage concepts:
- Storage medium vs storage device
- Secondary storage is non-volatile (data not lost when power is off)
- Virtual memory: memory space used by the processor when RAM is full
Storage devices list:
- Hard Disk Drive (HDD)
- Solid State Drive (SSD)
- Optical Disk Drives (CD/DVD/Blu‑ray)
- Flash Media
- Magnetic Tape
Hard Disk details:
- Structure: spindle, concentric platters, read/write head
- Performance factors: RPM (spindle speed), seek time (head movement to location)
- Read/write process: Reading changes magnetic field to electric current; writing changes current to magnetic field
Optical media details:
- CD: 700 MB
- DVD: ~4.5 GB (single) / 18 GB (dual-layer)
- Blu‑ray: 25 GB (single) / 50 GB (dual-layer)
- All common formats can be recordable (R); DVD/RW equivalents exist
Media types:
- Flash media: No moving parts; energy efficient and portable
- Magnetic tape: Used for backup/storage in some contexts
Data storage basics:
- All storage uses binary (bits: 0 or 1)
- HDD: read/write by changing magnetic states
- Optical: data as pits/pokes read by laser reflection
- Flash: data as charge levels in cells
- Magnetic tape: magnetic charge states on tape

Accessibility examples for devices:
- Braille keyboards
- Gesture interfaces for low mobility
Data size basics (LaTeX-ready):
8 ext{ bits} = 1 ext{ byte}
1\,\text{KiB} = 1024\,\text{bytes}
1\,\text{GiB} = 1024^3\,\text{bytes}
128\,\text{GiB} = 128 \times 1024^3\,\text{bytes}
{\text{bits}} = 128 \times 1024^3 \times 8 = 2^{40} \text{ bits} \approx 1.0995 \times 10^{12} \text{ bits}