IGCSE ICT: Computer Systems — Revision Notes

Condensed for the final weeks. For the full explanation, use the Computer Systems study guide.

Hardware and software

Hardware is physical; software is the programs.

• System software — operating system, utilities, device drivers, compilers. Runs the computer.
• Application software — word processors, spreadsheets, browsers, databases. Does the user’s work.

A device driver is system software, even though it relates to one device. That classification is examined regularly.

Input devices — justify the choice

Questions almost always ask which device for this situation and why. The answer always has two parts: name the device, then give the reason it suits that context.

Device	Context and reason
Barcode reader	Supermarket checkout — fast and avoids typing errors
Touchscreen	Public kiosk — intuitive, no training, no loose parts to damage or steal
OMR	Multiple-choice marking — reads pencil marks at high speed
OCR	Converting printed documents into editable text
MICR	Bank cheques — hard to forge and readable even when the cheque is dirty
Sensors	Monitoring and control — continuous automatic readings, no human error
Chip and PIN reader	Payment — secure, encrypted

Output devices

Monitor (soft copy), laser printer (high volume, fast, low cost per page), inkjet (cheap to buy, good photo quality, expensive per page), plotter (large accurate line drawings for CAD and maps), 3D printer (prototypes), speakers, and actuators in control systems.

Storage

	RAM	ROM
Volatility	Volatile — lost when power is off	Non-volatile
Contents	Programs and data in current use	Boot instructions
Writable	Yes	Read-only

Backing storage:

• Magnetic (hard disk) — very large capacity, low cost per GB, but moving parts and vulnerable to shock.
• Optical (CD/DVD/Blu-ray) — cheap and portable, but slower and smaller.
• Solid state (SSD, flash) — fast, silent, robust, low power; higher cost per GB.

Why an SSD suits a laptop: no moving parts so it survives being carried and knocked, lower power consumption so battery life improves, faster and silent. The trade-off is price per gigabyte.

Networks

• LAN — one site. WAN — geographically spread, often using third-party lines.
• Hardware: NIC, switch, router, cables or wireless access point, and a modem for internet access.

Wired versus wireless: wired is faster, more reliable and more secure; wireless is convenient, cheaper to install and allows mobility, but is slower, more prone to interference and easier to intercept.

Network security: firewalls, encryption, strong passwords, user access levels, and anti-malware.

Encryption does not stop data being intercepted — it makes intercepted data unreadable without the key. Saying it prevents interception is the standard error.

Health, safety and security

Health risks (long-term physical effects) and safety risks (immediate danger) are different categories, and questions ask for the hazard and its prevention together:

Health risk	Prevention
RSI	Wrist rest, correct posture, regular breaks
Eye strain	Anti-glare screen, breaks, suitable lighting
Back problems	Adjustable chair, screen at eye level

Safety risk	Prevention
Electrocution	Do not overload sockets; keep drinks away; check cables
Fire	Do not overload sockets; ventilate equipment; CO₂ extinguisher
Trailing cables	Cable ducts and tidy layout
Heavy equipment falling	Strong desks, secure placement

Data threats: viruses, hacking, phishing, pharming, smishing, spyware. Prevention: anti-virus software, firewalls, awareness training, checking URLs, and never following links in unsolicited messages.

Effects of ICT

On employment: jobs lost in repetitive manual and clerical roles; jobs created in IT support, network management and software development. The net effect is a change in the type of work rather than a simple loss, and retraining is the connecting issue.

Working patterns: teleworking, flexible hours, job sharing, compressed hours. Benefits include no commute, flexibility and lower office costs; drawbacks include isolation, distraction at home, and the difficulty of separating work from home life.

Microprocessor-controlled devices free time and allow remote operation, but can encourage a sedentary lifestyle and leave people dependent on technology.

Exam traps

• Classifying a device driver as application software.
• Naming a device without justifying it for the scenario given.
• Saying RAM stores data permanently.
• Confusing OMR with OCR.
• Saying encryption prevents interception.
• Giving a risk without its prevention.
• Saying ICT simply destroys jobs, with no mention of the jobs created.

Self-test

1. Distinguish system from application software, with two examples of each.
2. Give three differences between RAM and ROM.
3. Which input device suits a bank processing cheques, and why?
4. What does encryption actually achieve?
5. Give two health risks and two safety risks, each with a prevention.

Answers: 1. System software runs the computer — operating systems and device drivers; application software performs user tasks — word processors and browsers. 2. RAM is volatile, ROM is not; RAM holds data in current use, ROM holds boot instructions; RAM is writable, ROM is read-only. 3. MICR — the magnetic ink characters are difficult to forge and can be read reliably even if the cheque is dirty or creased. 4. It scrambles data so that anyone intercepting it cannot read it without the key; it does not prevent interception itself. 5. Health: RSI, prevented by wrist rests and breaks; eye strain, prevented by anti-glare screens and breaks. Safety: electrocution, prevented by not overloading sockets; trailing cables, prevented by cable ducts.