2.6 Virtual Memory

Virtual memory is not only physically existing memory. It is created by operating system in the partition of hard disk. When operating system is installed for first time, the system automatically allocate some space in partition which is used as virtual memory. 

Virtual memory is used to ease program loading in RAM by creating more space in RAM and moving back unnecessary programs to virtual memory. When more program is to be executed than the allocated free space in RAM, in such case virtual memory is used to move unnecessary or unused program for RAM. This created space in RAM to load new programs.