AQA · GCSE · Computer Science
Course version: 8525 · Version from Sept 2020
Systems architecture: Understand why secondary storage is required.
Secondary storage is needed because main memory (RAM) is volatile and limited.
Checked against the AQA 8525 specification (opens in a new tab) on .
- Point 25 of 30
Study notes
From the checked teaching notes for this specification point.
The idea
Secondary storage is needed because main memory (RAM) is volatile and limited. RAM holds the programs and data currently in use, but its contents are lost when power is removed, and it cannot hold everything a computer might need. Secondary storage provides non-volatile, long-term storage so files, programs and the operating system persist between sessions. It also offers far greater capacity than RAM at lower cost per byte, so large collections of documents, images, video and installed software can be kept. When a program runs, it is copied from secondary storage into RAM; when work is saved, it is written back to secondary storage.
For example: A laptop keeps its operating system and user files on a solid-state drive and loads them into RAM only when needed.
What earns the marks
- RAM is volatile, so its contents are lost when power is switched off; secondary storage is non-volatile and retains data.
- Secondary storage provides long-term storage of files, programs and the operating system between sessions.
- Secondary storage has much greater capacity than main memory and is cheaper per unit of storage.
- Programs and data are copied from secondary storage into RAM to run, and saved back to secondary storage.
- Secondary storage allows a computer to hold far more data than could fit in RAM at any one time.
Common mistakes and how to put them right
Saying secondary storage is faster than RAM.
Put it right: RAM is faster; secondary storage is slower but non-volatile and larger.
Claiming secondary storage is needed to make the computer run faster.
Put it right: It is needed for permanent, large-capacity storage, not for speed.
Confusing secondary storage with RAM as both being volatile.
Put it right: Only RAM is volatile; secondary storage keeps data without power.
Exam tips
- Link the answer explicitly to volatility: state that RAM loses data without power and secondary storage does not.
- Mention both capacity and cost per byte when explaining why secondary storage is used for large amounts of data.
- Describe the flow of a program: stored in secondary storage, copied to RAM to run, saved back to secondary storage.
Try the lesson
The start of the Systems architecture: Understand why secondary storage is required. lesson, made from checked teaching notes for this specification point.
Have a go first
A laptop is switched off and later switched back on. Why does the laptop need secondary storage such as a hard disk or SSD?
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