IGCSE · Practice questions · Magnetic, optical and solid-state storage

Magnets, lasers, gates.

Six original Cambridge-style questions on secondary storage, with mark-scheme style solutions.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

How, then examples.

Magnetic: platters, tracks and sectors, electromagnet on a read/write head. HDD.
Optical: laser creates and reads pits and lands. CD, DVD, Blu-ray.
Solid-state: NAND/NOR flash, control and floating gates, no moving parts. SSD, SD card, USB drive.
Choosing: link a feature (robust, capacity, cost, speed, portable) to the scenario.

Explain

[2 marks]

Explain why a computer needs secondary storage.

RAM is volatile, so data and programs would be lost when the power is turned off. ✓
Secondary storage is non-volatile, so it stores data and programs more permanently. ✓

Explain

[4 marks]

Describe how data is stored on a magnetic hard disk drive.

The disk has platters coated in magnetic material that spin. ✓
Each platter is divided into tracks and sectors. ✓
A read/write head moves across the platter to the correct track. ✓
An electromagnet magnetises areas in one of two directions to represent 1s and 0s (and reads them by detecting the direction). ✓

Explain

[3 marks]

Describe how data is read from a DVD.

The disc spins and a laser is shone onto its surface (along the spiral track). ✓
Pits and lands reflect the light differently (lands reflect, pits scatter). ✓
A sensor detects the reflected light and the changes are converted into binary. ✓

Explain

[3 marks]

Describe how solid-state (flash) memory stores data.

It uses NAND or NOR technology made of transistors. ✓
Each transistor has a control gate and a floating gate. ✓
Electrons are trapped in (or removed from) the floating gate to represent 1 or 0, and stay there without power. ✓

Apply

[3 marks]

A film company wants to send a copy of a new film to 5000 cinemas cheaply. Identify a suitable type of storage, give an example, and justify your choice.

Optical storage. ✓
For example Blu-ray disc. ✓
Discs are cheap to produce in large numbers and portable/light to post (and Blu-ray has enough capacity for a high-definition film). ✓

Analysis

[2 marks]

Give two reasons why an SSD is used instead of an HDD in a smartphone.

No moving parts, so it is more robust if the phone is dropped. ✓
It is smaller/lighter, uses less power and has faster access (any second reason). ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.