The Windows® 95 Virtual Display Device is composed of two VxD's. The first is VDD.VXD, supplied by Microsoft, and is combined by the Windows 95 Setup program into the file VMM32.VXD. This is referred to as the Main VDD, and it contains all virtual device functionality for standard VGA compatible devices. If your display adapter has hardware-specific needs that the Main VDD does not meet, you must write a virtual display minidriver (mini-VDD) to perform additional virtualization. The Main VDD and your mini-VDD are the two VxDs that make up the Virtual Display Device.
This chapter provides an overview of the Virtual Display subsystem and describes the Ring 3 function calls that a display driver can make into the Main VDD. For information about implementing a mini-VDD, see About Virtual Display Minidrivers. For information about VDD services available to mini-VDDs see About Virtual Display Device Services.