IGCSE ICT: Storage Devices and Media — Revision Notes

Condensed for the final weeks. For the full explanation, use the Storage Devices and Media study guide.

Device vs media — state it explicitly

Storage device = the hardware that reads/writes data (a disk drive, an SSD unit). Storage media = the physical material data is recorded onto — removable and separate for some technologies (a DVD disc vs its drive), sealed into one unit for others (an SSD). Using the two terms interchangeably is exactly what this topic penalises.

The three technology families

	Devices	Media	Strength	Weakness
Magnetic	Fixed/portable hard drives, tape drives	Magnetic hard disks, magnetic tape	Large capacity, low cost/GB	Slower access; damaged by strong magnetic fields/shock
Optical	CD, DVD, Blu-ray drives	CD, DVD, Blu-ray discs	Cheap, widely compatible	Slower/lower capacity; needs a clean, unscratched surface
Solid-state	SSDs, pen drives, flash drives	Memory cards (SD, xD, CFast)	No moving parts — fast, shock-resistant	Higher cost per GB

Optical discs also differ from each other mainly by capacity: Blu-ray > DVD > CD.

Why the technology choice depends on purpose

Magnetic tape, despite being the oldest listed technology, is still used for large-scale organisational backup because of its very low cost per gigabyte at huge capacities — even though its sequential (not random) access makes retrieving one specific file far slower than a hard disk or SSD. That trade-off is acceptable for long-term archival storage, not day-to-day access. Optical media’s read-only or write-once variants matter where data must not be alterable after writing — a guarantee neither magnetic nor solid-state media gives by default. “Advantages and disadvantages” in this topic usually hinge on purpose (everyday access speed vs long-term low-cost archiving vs portability), not one technology being unconditionally best.

Worked example: a photographer’s workflow

In-camera, during a shoot: solid-state media (SD/CFast memory card) — no moving parts to damage from vibration, compact and removable. Back at a desk: archive to a magnetic hard drive for low cost/GB across a large photo library, or back up to Blu-ray for a cheap, widely compatible offline format. Different technologies co-exist across one workflow’s different stages, rather than one being “best” throughout.

A subtle examinable point

A solid-state storage device (SSD) and solid-state storage media (SD card) use the same underlying technology, but the syllabus still expects you to identify which term a question is actually asking about — device or media — even when the technology behind them is identical.

Capacity, speed and cost together, not separately

A question asking you to “compare” two storage technologies expects more than one criterion named together, because the technologies rarely lead on every measure at once. Solid-state storage leads on speed and shock resistance but trails on cost per gigabyte; magnetic storage leads on cost per gigabyte at large capacities but trails on speed and shock resistance; optical storage leads on cost and universal compatibility but trails on both capacity and speed relative to the other two families. Treat these three criteria – capacity, speed, cost per gigabyte – alongside durability and portability as a fixed checklist to run through for any storage comparison question, rather than reaching for a single, often incomplete, “X is better than Y” answer.

Portability as a separate criterion from capacity

A common error is assuming a higher-capacity option is automatically the right recommendation. A field researcher needing to carry weeks of recorded data between remote sites with no reliable power supply may reasonably prioritise a small, rugged, solid-state portable drive over a higher-capacity magnetic hard drive, precisely because portability and shock resistance outweigh the benefit of extra capacity for that specific scenario – illustrating why “advantages and disadvantages” answers in this topic are scenario-dependent rather than fixed rankings.

Exam traps

• Using “device” and “media” interchangeably, when the question tests the distinction itself.
• Assuming one technology is unconditionally superior, rather than justifying a choice against the scenario’s actual purpose (speed, cost, portability, durability, write-once permanence).
• Giving a single-word justification (“fast”) instead of naming at least two relevant criteria together (e.g. “portable and shock-resistant”).
• Forgetting that optical media’s write-once property is itself sometimes the specific reason it is chosen, not just a limitation.
• Mixing up which optical format holds more: Blu-ray > DVD > CD, not the reverse.

Self-test

1. Distinguish between a storage device and storage medium, with one example of each.
2. Name the three storage technology families examined in this topic.
3. Why does magnetic tape remain in use for large-scale backup despite being slower to access a specific file than a hard disk?
4. State one property of optical media that can make it the deliberate choice over magnetic or solid-state media.
5. Order CD, DVD and Blu-ray by storage capacity, smallest to largest.
6. A photographer needs shock-resistant storage inside a moving camera. Which storage technology is most suitable, and why?

Answers: 1. A storage device is the hardware that reads/writes data (e.g. a DVD drive); storage media is the physical material data is recorded onto (e.g. a DVD disc). 2. Magnetic, optical, solid-state. 3. Its very low cost per gigabyte at very large capacities makes the trade-off of slower, sequential access acceptable for long-term archival storage rather than day-to-day access. 4. Its read-only or write-once variants guarantee data cannot be altered after writing. 5. CD, DVD, Blu-ray. 6. Solid-state (e.g. an SD memory card) — it has no moving parts, giving it resistance to shock and vibration that magnetic or optical technology cannot match.