Source : Free On-Line Dictionary of Computing

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        use of VM is the running of both outdated and current versions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.
     
        {Home (http://vmdev.gpl.ibm.com/)}.
     
        ["History of VM"(?), Melinda Varian, Princeton University].
     
        (1999-10-31)