Yes, but the same thing is basically true of most conventional file systems, e.g. various Unix/Linux file systems (although on most of those, files aren't spread across multiple drives, but there have been file systems that did that). But that description is, in some sense, just what classic virtual memory (paging) does. The crucial difference is in what the _user sees_: in a normal virtual memory system, a process' address space is a simple one-dimensional array of bytes/words. In a single-level-store (sometimes called 'segmentation'), a process' address space is two dimensional: segment along one axis, address within segment along the other: https://en.wikipedia.org/wiki/Single-level_store Of course, one can have segmentation (in the sense of 'what the process sees') _without_ virtual memory (either paging, or swapping entire segments), but most systems that implemented segmentation also did virtual memory too; Multics, and the family of IBM systems of which the AS/400 is a later member, both did. Noel