[W/K] :: virtual machine

  virtual machine
       
          1. An abstract machine for which an interpreter exists.
          Virtual machines are often used in the implementation of
          portable executors for high-level languages.  The HLL is
          compiled into code for the virtual machine (an intermediate
          language) which is then executed by an interpreter written
          in assembly language or some other portable language like
          C.
       
          Examples are Core War, Java Virtual Machine, OCODE,
          OS/2, POPLOG, Portable Scheme Interpreter, Portable
          Standard Lisp, Parallel Virtual Machine, Sequential Parlog
          Machine, SNOBOL Implementation Language, SODA,
          Smalltalk.
       
          2. A software emulation of a physical computing environment.
       
          The term gave rise to the name of IBM's VM operating
          system whose task is to provide one or more simultaneous
          execution environments in which operating systems or other
          programs may execute as though they were running "on the bare
          iron", that is, without an eveloping Control Program.  A major
          use of VM is the running of both outdated and current versions
          of the same operating system on a single CPU complex for the
          purpose of system migration, thereby obviating the need for a
          second processor.
       
          (2002-04-15)
       
       

  Virtual Machine
       
           (VM) An IBM pseudo-{operating system
          hypervisor running on IBM 370, ESA and IBM 390
          architecture computers.
       
          VM comprises CP ({Control Program) and CMS ({Conversational
          Monitor System) providing Hypervisor and personal computing
          environments respectively.  VM became most used in the early
          1980s as a Hypervisor for multiple DOS/VS and DOS/VSE
          systems and as IBM's internal operating system of choice.  It
          declined rapidly following widespread adoption of the IBM PC
          and hardware partitioning in microcode on IBM mainframes
          after the IBM 3090.
       
          VM has been known as VM/SP (System Product, the successor to
          CP/67), VM/XA, and currently as VM/ESA (Enterprise Systems
          Architecture).  VM/ESA is still in used in 1999, featuring a
          web interface, Java, and DB2.  It is still a major IBM
          operating system.
       
          http://vmdev.gpl.ibm.com/).html">Home (http://vmdev.gpl.ibm.com/).
       
          ["History of VM"(?), Melinda Varian, Princeton University].
       
          (1999-10-31)