A. Virtual Memory makes up for the lack of RAM in
computers by using space on the hard disk as memory, Virtual Memory. When
the actual RAM fills up (actually its before the RAM fills) then virtual
memory is created on the hard disk. When physical memory runs out, the
Virtual Memory Manager chooses sections of memory that have not been
recently used and are of low priority and writes them to the swap file.
This process is hidden from applications, and applications views both
virtual and actual memory as the same.
Each application that runs under Windows NT is given its own virtual
address space of 4GB (2GB for the application, 2GB for the operating
system).
The problem with Virtual Memory is that as it writes and reads to the
hard disk, this is much slower than actual RAM. This is
why if an NT system does not have enough memory it will run very slowly.