Question

paging in os

Answer 1

When the real (core) memory of a machine is used up, the OS will try to transfer pages (usually 4096 bytes per page) of memory to a designated space on the hard drive in an attempt to make it seem like there's more memory than there is. When the page of memory is needed, it's brought back into core.

One problem with this is that hard drives are regarded as being about 1000 times slower than memory, so the machine slows down noticeably. Mouse clicks can take a few seconds to register.

If the machine thrashes, mouse clicks can take a minute or two to register. Thrashing is when the machine is doing so much paging that it doesn't do any useful work, it's too busy swapping pages of memory to and from disk.

All this, and with memory being cheap, be generous with the memory when buying a machine and the thing will probably run real good for a surprisingly long time.