Editing Device driver (section)

==Virtual device drivers==
Virtual device drivers represent a particular variant of device drivers. They are used to emulate a hardware device, particularly in [[virtual machine|virtualization]] environments, for example when a [[DOS]] program is run on a [[Microsoft Windows]] computer or when a guest [[operating system]] is run on, for example, a [[Xen]] host. Instead of enabling the guest operating system to dialog with hardware, virtual device drivers take the opposite role and emulates a piece of hardware, so that the guest operating system and its drivers running inside a [[virtual machine]] can have the illusion of accessing real hardware. Attempts by the guest operating system to access the hardware are routed to the virtual device driver in the host operating system as e.g.,&nbsp;[[function call]]s. The virtual device driver can also send simulated processor-level events like [[interrupt]]s into the virtual machine.

Virtual devices may also operate in a non-virtualized environment. For example, a virtual [[network adapter]] is used with a [[virtual private network]], while a virtual [[Hard disk drive|disk]] device is used with [[iSCSI]]. A good example for virtual device drivers can be [[Daemon Tools]].

There are several variants of virtual device drivers, such as [[VxD]]s, [[VLM (NetWare)|VLM]]s, and VDDs.