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Primary Storage: RAM and ROM

FoundationHigherAQA

Revise Primary Storage: RAM and ROM for GCSE Computer Science with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA GCSE Computer Science (8525). RAM is volatile and holds running programs; ROM is non-volatile and holds start-up instructions.

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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA specification. Every worksheet comes with a full mark scheme.

Foundation

WorksheetFoundation · PDFMark SchemeFoundation · PDF

Higher

WorksheetHigher · PDFMark SchemeHigher · PDF

Topic overview

Primary storage is memory directly accessible by the CPU. The two types required are RAM and ROM, and they differ in almost every respect.

RAM is random access memory. It is volatile, losing its contents when power is removed. It holds the programs and data currently in use, and both reading and writing are possible. Its contents change constantly as programs open and close.

ROM is read-only memory. It is non-volatile, retaining its contents without power. It holds the instructions the computer needs to start up, usually the bootstrap program that loads the operating system. It cannot normally be written to, which is why its contents cannot be lost or accidentally altered.

Revision notes

RAM

Volatile: contents are lost when power is removed.

Holds the programs and data currently in use. Can be both read from and written to. Its contents change constantly as programs are opened and closed.

ROM

Non-volatile: contents are retained without power.

Holds the instructions needed to start the computer, usually the bootstrap that loads the operating system. Cannot normally be written to, so its contents cannot be lost or accidentally changed.

Virtual memory

When RAM is full, the operating system moves less-used data to secondary storage.

This area is called virtual memory. It allows more programs to run than RAM alone would allow, but it is much slower, because secondary storage is far slower than RAM.

Key points

  • Primary storage is directly accessible by the CPU.
  • RAM is volatile and loses data without power.
  • RAM holds programs and data currently in use.
  • ROM is non-volatile and retains data.
  • ROM holds the start-up instructions.
  • Virtual memory extends RAM using secondary storage.

Worked examples

Example 1

State two differences between RAM and ROM. [2 marks]

Working

RAM is volatile and loses its contents without power, whereas ROM is non-volatile and retains themgive the first difference
RAM can be written to as well as read, whereas ROM cannot normally be written togive the second difference

Example 2

Explain why ROM is used to hold the start-up instructions. [2 marks]

Working

ROM is non-volatile, so the instructions remain when the computer is switched offstate the property
meaning they are available immediately when the computer is turned back on, before any storage is accessibleexplain the benefit

Example 3

Explain why using virtual memory slows a computer down. [2 marks]

Working

Virtual memory uses secondary storage, which is much slower to access than RAMstate the reason
so moving data between RAM and secondary storage takes noticeable timeexplain the effect

Common mistakes

  • Saying ROM is volatile.

    It is non-volatile — that is why it holds start-up instructions.

  • Saying RAM stores files permanently.

    It is volatile; permanent storage is secondary.

  • Confusing virtual memory with RAM.

    Virtual memory is secondary storage used as extra RAM.

  • Saying virtual memory is faster.

    It is much slower than real RAM.

Exam tips

  • Contrast RAM and ROM on volatility and writability.
  • Explain ROM's role through non-volatility.
  • Link virtual memory slowness to secondary storage speed.
  • Say primary storage is directly CPU-accessible.

Key terms

RAM
Volatile primary storage holding current programs and data.
ROM
Non-volatile primary storage holding start-up instructions.
Volatile
Losing contents when power is removed.
Virtual memory
Secondary storage used as an extension of RAM.

Related topics

Written and reviewed against the current AQA specification. Spotted an error? Let us know.