sentences:  It originally meant what is now usually called virtual memory, which was introduced in 1962 by the Atlas system at Manchester.It now usually refers to the organization of a computing system in which there are no files, only persistent objects (sometimes called segments), which are mapped into processes' address spaces (which consist entirely of a collection of mapped objects).The entire storage of the computer is thought of as a single two-dimensional plane of addresses (segment, and address within segment).