Wave Systems Corp. (fka WAVXQ)

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In computing, a hypervisor (also: virtual machine monitor) is a virtualization platform that allows multiple operating systems to run on a host computer at the same time. The term usually refers to an implementation using full virtualization. Hypervisors are currently classified in two types.

* Type 1 hypervisor (or Type 1 virtual machine monitor) is software that runs directly on a given hardware platform (as an operating system control program). A "guest" operating system thus runs at the second level above the hardware. The classic type 1 hypervisor was CP/CMS, developed at IBM in the 1960s, ancestor of IBM's current z/VM. More recent examples are Xen, VMware's ESX Server, and Sun's Hypervisor (released in 2005).

* Type 2 hypervisor (or Type 2 virtual machine monitor) is software that runs within an operating system environment. A "guest" operating system thus runs at the third level above the hardware. Examples include VMware server and Microsoft Virtual Server.

The term hypervisor apparently originated in IBM's CP-370 reimplementation of CP-67 for the System/370, released in 1972 as VM/370. The term hypervisor call referred to the paravirtualization interface, by which a "guest" operating system could access services directly from the (higher-level) control program – analogous to making a "supervisor call" to the (same level) operating system. (The term 'supervisor' refers to the operating system kernel, which on IBM mainframes runs in supervisor state.)

http://en.wikipedia.org/wiki/Hypervisor