Virtual memory is a memory management technique used by modern operating systems to create an abstraction of a large and contiguous block of memory, even if the physical memory (RAM) is limited. It allows a computer to compensate for physical memory shortages by temporarily transferring data from random access memory (RAM) to disk storage.

Address Space Abstraction Virtual memory provides each process with its own virtual address space, which can be larger than the actual physical memory. This means that programs can use more memory than is physically available.

Paging The virtual memory system divides memory into chunks called "pages." When a program needs more memory, the system can move pages in and out of physical memory as needed. This process is called paging or swapping.

Page Tables The operating system maintains a page table for each process that maps virtual addresses to physical addresses. When a program accesses a memory location, the address is translated from the virtual address to the physical address using this table.

Demand Paging Not all pages are loaded into physical memory at once. When a program accesses a page that is not currently in physical memory, a page fault occurs. The operating system then loads the required page from disk into RAM and updates the page table.

Memory Overcommitment Virtual memory allows the system to overcommit memory, meaning it can allocate more virtual memory to processes than the physical memory available. This is feasible because not all allocated memory is used at the same time.

Protection and Isolation Each process operates in its own virtual address space, which helps in isolating processes from one another and prevents them from interfering with each other's memory.

Virtual memory enhances system performance and multitasking capabilities, providing the illusion of a larger and more flexible memory space than what is physically present.