Memory management is the most important parts of the operating system.early days of computing, there has been a need for more memory than exists physically in a system.Virtual memory makes the system appear to have more memory than it actually has by sharing it between competing processes as they need it.
The operating system makes the system appear as if it has a larger amount of memory than it actually has. The virtual memory can be many times larger than the physical memory in the system.
Each process in the system has its own virtual address space. These virtual address spaces are completely separate from each other and so a process running one application cannot affect another. Also, the hardware virtual memory mechanisms allow areas of memory to be protected against writing. This protects code and data from being overwritten by rogue applications.
