If there were only 4096 words available, any address above 4095 was useless. If, however, we re-map the addresses to start at 4096, instead of at 0, then when an address between 0 and 4095 is called, the words from 4096 to 8191 will be referenced instead. The technique for automatic overlaying is called paging, and the blocks of memory are called pages. The total memory area a machine can refer to is called the virtual address space, while the actual memory available is called the physical address space. A memory map or page table relates virtual to physical address space.
Virtual memory acts just like normal memory as far as the programmer is concerned.
For this reason, it is considered transparent. Implementation of Paging A disk on which to keep the entire store of data is necessary to implement virtual memory. This should be considered the original, while data in main memory can be considered to be copies. These copies, when altered, will need to be written back to the original location at some point. Both virtual address space and physical address space are broken up into equal sized pages.