The difference between RAM and ROM

1.2.1 Primary Storage (memory)

Primary Storage (memory) — Note 2 of 6

What you need to know

RAM and ROM are both types of primary storage, but they have very different characteristics. Understanding their differences — particularly volatility, read/write capability, and purpose — is essential.

What to know

Key terms

Exam tipCommon mistake

Volatile Memory: Memory that loses its contents when the power is turned off.
RAMRandom Access Memory: Volatile memory that holds data and programs currently in use. Contents are LOST when the power is turned off.
RAM is read AND write — data can be changed. ROM is read-only — data cannot normally be modified.
RAM is volatile (loses data without power). ROM is non-volatile (keeps data without power).
ROMRead-Only Memory: Non-volatile memory that stores firmware essential for booting up. Contents are RETAINED when the power is off.
Common mistake: Saying ROM 'cannot store anything'. It CAN store data — it stores the boot-up instructions (firmware). It just cannot be written to during normal operation.

Exam technique

Tip:A common exam question compares RAM and ROM. Always mention: volatility, read/write capability, and what each stores.
Tip:When asked 'State the difference between RAM and ROM', you MUST give BOTH sides. E.g. 'RAM is volatile, ROM is non-volatile'. Just saying 'RAM is volatile' is not enough on its own.

Example:'Sat Nav: ROM stores the boot-up sequence. RAM stores the currently open maps and routes. RAM contents are lost when turned off.'

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