Hi,
Virtual Memory is a concept in which user of a system feels 
to have a large physical memory(Main) that actually does 
not available.
for example U feel unlimited memory(Main) thougn u have 
only in MB's.

If OS did not have this concept then user has to manage the 
memory and in deed can run only a few program at a time.
It means here comes a limit on the efficiency of the system.

byeeeeeeeeeeeeeeeeee.