In computing refers to the act of creating a virtual (rather than actual) version of something, including but not limited to a virtual computer hardware platform, operating system (OS), storage device, or computer network resources.
Virtualization began in 1960s main frame computers as a method of logically dividing the system resources provided by mainframe between different applications. Since then, the meaning of the term has broadened.



In July 2006 Microsoft released the Windows version as a free product. In August 2006 Microsoft announced the Macintosh version would not be ported to Intel based Macintosh computers, effectively discontinuing the product as Power PC- based Macintosh computers are no longer manufactured. The newest released, Windows Virtual PC, does not run on versions of Windows earlier than Windows 7, and does not officially support MS-DOS or operating systems earlier than Windows XP professional SP3 as guests. The older version which supports a wider range of hosts and guest operating systems remain available.
Virtual PC virtualizes a standard PC and its associated hardware. Supported Windows operating systems can run inside Virtual PC. Other operating systems such as Linux may run, but are not officially supported, and Microsoft does not provide the necessary “ Virtual Machine Additions” (which includes essential drivers) for Linux. Connectix Virtual PC, Microsoft Virtual PC 2004, Microsoft Virtual PC-2007.
Desktop virtualization is the concept of separating the logical desktop from the physical machine. One form of desktop virtualization virtual desktop infrastructure (VDI) can be thought of as a more advanced form of hardware virtualization. Rather than interacting with a host computer directly via a keyboard, mouse, and monitor, the user interacts with the host computer using another desktop computer or mobile device by means of a network connection, such as a LAN, Wireless LAN, or even the internet. In addition, the host computer in this scenario becomes a server computer capable of hosting multiple virtual machines at the same time for multiple users.
Modern operating systems such as Microsoft Windows and Linux can include limited application virtualization. For example, Windows 7 provides W3indows XP mode that enables older Windows XP application to run unmodified on Windows 7. Full application virtualization requires a virtualization layers. Application virtualization layers replace part of the run time environment normally provided by the operating system. The layer intercepts all disk operations of virtualized applications and transparently redirects them to a virtualized location, often a single file. The application remains unaware that it accesses a virtual resource instead of a physical one. Since the application is now working with one file instead of many files spread throughout the system, it becomes easy to run the application on a different computer and previously incompatible applications can be run side-by-side. Example of this technology for the Windows platform include, AppZero,BoxedApp, Cameyo, Ceedo, AppLidis, Evalaze, InstallFree, 2x Software, Citrix XenApp, Systancia, Novell Zenworks Application Virtualization, Numecent Application Jukebox, Microsoft Application Virtualization, Software Virtualization Solution, Spoon (formerly Xencode), Symantec Workspace Virtualization and Workspace Streaming, VMware ThinApp, P-apps and Oracle Secure Global Desktop.
Hardware-assisted virtualization is a way of improving efficient virtualization. It involves CPUs that provide support for virtualization in hardware, and other hardware components that help improves the performance of a guest environment. Hardware virtualization can be viewed as a part of an overall trend in enterprise IT that includes autonomic computing a scenario in which the IT environment will be able to manage itself based on perceived activity and utility computing, in which computer processing power is seen as a utility that clients can pay for only as needed. The usual goal of virtualization is to centralize administrative tasks while improving scalability and over all hardware-0resource utilization. With virtualization, several operating systems can be run in parallel on a single central processing unit (CPU). This parallelism tends to reduce our head costs and differ from multitasking w/c involves running several programs on the same OS. Using virtualization an enterprise can better manage updates and rapid changes to the operating system and applications without disrupting the user. Ultimately, virtualization dramatically improves efficiency and availability of resources and application in an organization. Instead of relying on the old model of one server, one application “that leads to underutilized resources, virtual resources are dynamically applied to meet business needs without any excess fat “(Consonus Tech).
Hardware virtualization is not the same as hardware emulation. In hardware emulation a piece of hard imitates another, while in hardware virtualization; a hypervisor (a piece of software) imitates a particular piece of computer hardware or the entire computer. Furthermore, a hypervisor is not the same as an emulator, both are computer programs that inflate hardware. But their domain of use in language differs.

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