What is the difference between RAM and ROM, and what is virtual memory used for?
The purpose and characteristics of RAM and ROM, the difference between volatile and non-volatile memory, and the purpose of virtual memory.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on memory, covering the purpose and characteristics of RAM and ROM, the meaning of volatile and non-volatile, the role of the BIOS in ROM, and how virtual memory uses secondary storage to extend RAM when it is full.
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What this topic is asking
WJEC wants you to know the purpose and characteristics of RAM and ROM, the difference between volatile and non-volatile memory, and what virtual memory is and why it is used. This is part of the Hardware content in Unit 1 of WJEC GCSE Computer Science (3500).
RAM
ROM
Volatile and non-volatile
Virtual memory
Try this
Q1. State whether RAM is volatile or non-volatile and what this means. [2 marks]
- Cue. RAM is volatile, meaning its contents are lost when the power is turned off.
Q2. State one reason why a computer with very little RAM might run slowly. [1 mark]
- Cue. It must rely heavily on slower virtual memory once the RAM is full.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC-style Unit 14 marksDescribe the differences between RAM and ROM, referring to what each stores and whether it is volatile.Show worked answer →
A Unit 1 memory question. RAM (random access memory) is the computer's main working memory: it holds the programs and data currently in use, and the CPU reads from and writes to it (1 mark). RAM is volatile, meaning its contents are lost when the power is turned off (1 mark). ROM (read only memory) stores data that does not change, in particular the startup instructions (the BIOS or boot program) needed to start the computer (1 mark). ROM is non-volatile, so it keeps its contents without power and normally cannot be changed by the user (1 mark). Markers reward working memory versus startup instructions and volatile versus non-volatile. A common error is to swap volatile and non-volatile, or to say ROM stores the user's files.
WJEC-style Unit 13 marksExplain what virtual memory is and why it is used.Show worked answer →
A Unit 1 explain question. Virtual memory is an area of secondary storage (such as the hard drive or SSD) that is used as if it were extra RAM (1 mark). When the RAM becomes full, the operating system moves data that is not currently needed from RAM into virtual memory, freeing up RAM for the active program (1 mark). This lets the computer keep running, or run larger programs, than the physical RAM alone would allow, although it is slower because secondary storage is slower than RAM (1 mark). Markers reward using secondary storage as extra RAM and freeing RAM when full. A common error is to say virtual memory is faster than RAM, when it is actually slower.
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