Hypervisor

A hypervisor is the software layer that creates and manages virtual machines, allocating a physical computer's processor, memory and other hardware among several separate guest operating systems running on it at once. The concept and the earliest working hypervisors emerged alongside virtual machine technology itself at IBM's Cambridge Scientific Center in the late 1960s, in the CP-40 and CP-67 systems' control program, which later computer scientists came to call a hypervisor to distinguish it from the ordinary operating-system supervisor it sat beneath. Hypervisors are commonly divided into type 1, which runs directly on the host's hardware, and type 2, which runs as a program atop a conventional operating system, a distinction that became commercially significant once products such as the open-source Xen project, released in 2003, and VMware's ESX server brought hypervisor-based virtualization to mainstream server computing.