Single-level store

Single-level storage (SLS) or single-level memory is a computer storage term which has had two meanings. The two meanings are related in that in both, pages of memory may be in primary storage (RAM) or in secondary storage (disk), and that the physical location of a page is unimportant to a process. The term originally referred to what is now usually called virtual memory, which was introduced in 1962 by the Atlas system at the University of Manchester. In modern usage, the term usually refers to the organization of a computing system in which there are no , 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). The persistent object concept was first introduced by Multics in the mid-1960s, in a project shared by MIT, General Electric and Bell Labs. It also was implemented as virtual memory, with the actual physical implementation including a number of levels of storage types. (Multics, for instance, had three levels originally: main memory, a high-speed drum, and disks.) IBM holds patents to single-level storage as implemented in the IBM i operating system on IBM Power Systems and its predecessors as far back as the System/38 that was released in 1978. In early systems, there was a clear distinction between main memory and any secondary storage. In order to process data, programs would use explicit code to read data from secondary storage into main memory, manipulate it in main memory, and then use more code to write it back out to secondary storage again. This distinction remains to this day in most operating systems (OS). In the 1960s, timesharing and multiprogramming were introduced. In these systems, more than one program might be running at the same time, and each desires to have its own memory to work with.

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Concepts associés (3)

Multics

Multics (acronyme de MULTiplexed Information and Computing Service) est le nom d'un système d'exploitation en temps partagé. Ce projet a été lancé en 1964, par Fernando Corbató et Jerry Saltzer. Le projet Multics a marqué la conception des systèmes d'exploitation notamment après la réutilisation et la diffusion dans le système Unix de nombreux éléments qui en faisait un système novateur : système de fichier hiérarchique, temps partagé, multitâche préemptif, multiutilisateur, sécurité.

Single-level store

Système d'exploitation

En informatique, un système d'exploitation (souvent appelé OS — de l'anglais operating system — ou parfois SE — en français) est un ensemble de programmes qui dirige l'utilisation des ressources d'un ordinateur par des logiciels applicatifs. Il reçoit des demandes d'utilisation des ressources de l'ordinateur de la part des logiciels applicatifs. Le système d'exploitation gère les demandes ainsi que les ressources nécessaires évitant les interférences entre les logiciels.