Virtual device driver definition
A virtual device driver is a special type of software device driver designed for Microsoft Windows/386 2.x — the 386 enhanced mode of Windows 3.x and Windows 9x Windows 9x (95, 98, and Me) operating systems (OS). It is often simply called “VxD,” which is short for “virtual xxx driver” (where “xxx” is a stand-in for the particular device).
VxD is only used in legacy systems today. It has been replaced by the Windows Driver Model (WDM) in Windows 2000, NT, and later editions.
See also: device driver, computer system, kernel
Virtual device driver functions
VxDs allow an OS to communicate with and control hardware devices (such as printers, disk drives, and graphics cards). They can manage interrupts, handle hardware events, and provide an interface for higher-level software components.
To perform low-level operations and interact closely with the operating system's core components, VxDs operate in kernel mode — they have direct access to the system's hardware and memory.
Because Windows 9x operating systems were based on a 16-bit architecture, VxDs were written in 16-bit x86 assembly language — this is in contrast to later versions of Windows, which transitioned to a 32-bit and then 64-bit architecture.
