(a) Give two differences between RAM and ROM. [2]
(b) A computer is running several large programs and its RAM is full. Explain how virtual memory allows the computer to keep running. [3]
- (a) Any one difference, comparing both: RAM is volatile / loses contents when power is off, ROM is non-volatile; RAM can be read and written (contents change), ROM is read only (contents fixed); RAM holds programs / data currently in use, ROM holds the boot-up instructions / BIOS; allow RAM usually has a larger capacity than ROM(1)
- (a) A second, different difference from the list above(1)
- (b) Part of secondary storage (e.g. the hard disk) is used as if it were RAM / as virtual memory(1)
- (b) Data / programs not currently being used are moved (swapped) from RAM to virtual memory, freeing space in RAM for the data / programs that are needed(1)
- (b) When the swapped-out data / programs are needed again they are moved back into RAM (and other data is swapped out); allow so more programs can stay open than RAM alone could hold; ignore 'it is slower' (true, but not how it works)(1)
- Answer: (a) RAM volatile / read-write; ROM non-volatile / read-only. (b) Part of secondary storage used as extra RAM; inactive data swapped out and back when needed
- Examiner tip: Each difference must cover both memories, e.g. 'RAM is volatile but ROM is non-volatile' – a fact about RAM alone may not score.