Outline the reasons why an operating system may need to use virtual memory.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

1. [1] Virtual memory is used when RAM is running low
2. [1] ...such as when a computer is running many processes at once.
3. [1] Virtual memory may be used for efficient use of RAM / the processor
4. [1] ...such as if data / programs are not immediately needed, they can be moved from RAM to virtual memory
5. [1] Disk thrashing is a problem that may occur when frequent transfers between main memory and secondary memory take place // Disk thrashing is a problem that may occur when virtual memory is being used
6. [1] As main memory fills up, more pages need to be swapped in and out of secondary/virtual memory
7. [1] This swapping leads to a very high rate of hard disk head movements
8. [1] Eventually, more time is spent swapping the pages/data than processing the data.