Virtual machine

also called system virtual machine. a self-contained operating environment that behaves as if it is a separate computer, with no access to the host operating system:
when an application runs in a virtual machine, there is little chance that it will damage files or applications in the host system.
also called process virtual machine, application virtual machine. a platform-independent execution environment that itself runs as a normal application inside a host operating system and enables a program written for the virtual machine to execute the same way on any platform:
jvm, written in the java programming language, is the most common process virtual machine.
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 part-tioning 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)

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 -ssembly 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, sn-bol 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)