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

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   use of VM is the running of both outdated and current versions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