Solid-state Storage (Flash Memory) — Memory and Storage | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 5% of your exam marks.

stable

Rare

Stable5%

RAM vs ROM and primary vs secondary storage comparisons appear regularly.

Solid-state storage has no moving parts. It stores binary data as electrical charge trapped in tiny transistor cells on a flash-memory chip.

How a solid-state drive (SSD) works

The drive is a chip (or several chips) containing millions of tiny memory cells.
Each cell contains a special transistor with a floating gate: a small conductor sandwiched between insulating layers that can hold an electrical charge. The charge stays in place even after the power is removed, which is what makes flash memory non-volatile.
An erased cell holds no trapped charge on its floating gate, and the cell reads as a 1.
To store a 0, a high voltage pushes electrons through the insulator and traps them on the floating gate; a cell with trapped charge reads as a 0.
To read, the cell is checked for whether the floating gate is charged: no charge gives a 1, trapped charge gives a 0.

Because there are no moving parts, the drive can be small, silent, and resistant to shock. Reading and writing also happens entirely electronically, which is much faster than mechanically moving a head over a spinning disc.

Common solid-state devices:

(solid-state drives) inside laptops and desktops, replacing magnetic HDDs as the primary internal drive
USB flash drives
SD cards in cameras and phones
Internal storage of smartphones and tablets

Advantages and disadvantages

Advantages	Disadvantages
Very fast read/write	Expensive per gigabyte compared to HDDs
No moving parts: durable, shock-resistant, silent	Limited number of write cycles (cells eventually wear out after billions of writes)
Small, light, portable	Smaller maximum capacities than the biggest HDDs
Low power use (good for laptops)

Exam tip

Give features of solid-state storage

What comes up: "Give three features of solid-state storage" or a "which storage type is best for this device?" question asking you to justify solid-state for a smartphone or laptop.

Write (three marks): (1) Solid-state storage has no moving parts, making it durable and shock-resistant. (2) It stores data by controlling the flow of electrons through transistor cells using NAND flash technology. (3) It has fast read/write speeds, so files and applications load quickly.

Watch out: the mark scheme awards a separate mark for "no moving parts" and a further mark for the consequence (durable/robust). When justifying solid-state for a portable device, always pair the feature with its benefit — "no moving parts, so it is durable" scores two marks, but "no moving parts" alone scores only one. Do not describe solid-state as using a laser (that is optical) or a spinning platter (that is magnetic).