Editing VxD (section)

== History ==
Prior to the advent of Windows, [[DOS]] applications would either communicate directly with the various pieces of hardware (responding to [[interrupt]]s, reading and writing [[device memory]] etc.) or go through a DOS [[device driver]]. As DOS was not multitasking, each application would have exclusive and complete control over the hardware while running. Though [[Microsoft Windows|Windows]] applications don't often communicate directly with hardware, it was the only way for Windows drivers; and still is in the [[real mode|real]] and standard modes of Windows 3.x.

[[Windows/386]] and onward allowed multiple DOS applications to execute concurrently by executing each within its own [[virtual DOS machine|virtual machine]]. To share physical resources among these virtual machines, Microsoft introduced virtual device drivers. These drivers solved issues relating to conflicting usage of physical resources by intercepting calls to the hardware. Instead of a [[Input/output#Port-mapped I/O|machine port]] representing an actual device, it would represent a "virtual" device, which could be managed by the operating system.