Virtual Machine

Virtual Machine
Virtual Machine/ESA
Virtual Machine/System Product
Virtual Machine/XA
VM
VM/ESA
VM/SP
VM/XA

   <operating system> (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/).

   ["History of VM"(?), Melinda Varian, Princeton University].

   (1999-10-31)
    

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   use of VM is the running of both outdated and current versions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)