Virtual Memory System

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The VMS (Virtual Memory System) operating system (OS) is a multiuser, multiprocessing OS that was designed by Digital (now Compaq) in conjunction with their 32-bit VAX processor for use use in time sharing, batch processing, and transaction processing. VMS also runs on the 64-bit Alpha processor and will be ported to the 64-bit Intel processor.

VMS also supports clustering (called VAXcluster or later VMScluster), where multiple systems share processing, job queues, print queues, and disk storage, either over a special computer interconnect (CI) bus or over Ethernet (called a LAVC, for local area network VMS cluster).

VMS can be divided into three layers

  • the kernel, made up of input/output, memory management, and process/time management subsystems
  • core services, made up of DCL, RMS, DECwindows, and the RTLs
  • utility programs for support, system management, and programming

DCL - Digital Command Language - command line interface
DECwindows - Digital's implementation of the X Window System
RMS - Record Management Services - high-level, language/device-independent IO
RTL - Runtime Libraries - shared routines and functions, callable from any language

VMS was originally developed by (project leader?) Dave Cutler, who had earler developed Digital's RSX-11M operating system. Cutler was hired in 1988 by Microsoft to build the team that developed Windows NT.