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This chapter provides a quick overview of the system. It is intended to introduce you to the concepts of the system; these concepts will then be expanded on in the remaining chapters of the manual.
The system's main function is to allow multiple virtual machines to execute concurrently on a single PC style computer (386-based and above). A simple operating system has been designed and implemented to provide the basic support for multiple tasks. On top of this operating system we have implemented a number of software modules, each virtualising a hardware resource (providing a software replica of the device).
Using a standard operating system task (i.e. a thread of control) virtual machines (a `copy' of a real machine, often shortened to just VM) can be created. This virtual machine has a set of virtual devices installed in it before being started. To a program (usually an operating system) running in a virtual machine, there is no difference between executing in a real machine or a virtual machine. The only noticeable difference should be the performance of the program in the virtual machine; since every access to a piece of hardware is somehow emulated a substantial overhead is incurred.
Although the objective of the system is to allow the creation of multiple virtual machines a number of other subsystems had to be created before this could be achieved
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