Virtual Memory:-

• It is the separation of user logical memory from physical memory.

• Only part of the program needs to be in memory for execution.

• It allows pages to be swapped in and out.

• Logical address space can therefore be much larger than physical address space.

• It can be implemented by

Demand paging

Demand segmentation



Demand Paging:-

• A page can be fetched into memory at the time of requirement.

Less I/O is needed.

Less memory is needed.

Faster response is needed.

More users are needed.

• Page is needed => reference to it

invalid reference => abort

not-in-memory => bring to memory