RAM and ROM

1.1.3 Input, output and storage

Input, output and storage — Note 3 of 4

Candidates need to understand the purpose of ROM and RAM within a computer system, their characteristics, and the role they play in the running of a range of different computers e.g. mobile devices, embedded systems etc

What you need to know

RAM and ROM are both types of primary memory directly accessible by the processor. RAM is volatile working memory for programs and data in use; ROM is non-volatile memory holding instructions that must not be lost when the power is off.

What to know

RAM is larger than ROM and its contents change constantly as programs are loaded and closed.
In embedded systems (e.g. a washing machine) the whole control program is often stored in ROM, with a small amount of RAM for data during operation.

Key terms

Exam tipCommon mistake

RAMRandom Access Memory: Volatile memory that holds the operating system, programs and data currently in use. It can be read from and written to.
Mobile devices use RAM for running apps and flash memory to store the OS and apps permanently.
ROMRead Only Memory: Non-volatile memory whose contents are kept without power. It holds firmware such as the start-up (boot) instructions and cannot normally be changed.
ROM in a PC holds the BIOS/UEFI and the bootstrap loader. Modern 'ROM' is often flash memory so it can be updated.
Common mistake: Saying ROM stores the operating system on a PC. The OS is stored on secondary storage; ROM stores the instructions to START loading it.

Exam technique

Tip:When comparing RAM and ROM give both sides of each point: 'RAM is volatile whereas ROM is non-volatile'.

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Practise 1.1.3 questions

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