This is Microsoft’s multimedia plug-in engine for Windows 95, 98, 2000, ME and NT, initially designed for the purpose of eliminating compatibility issues with devices for multimedia [especially video game] developers (in other words, not limiting enhanced multimedia software to the use of only a few ‘specialized’ audio or video hardware devices). Any Windows application supporting DirectX is able to host DirectX plug-ins, audio processing effects that can be used in real time while mixing. Some DirectX host applications also allow DirectX plug-ins to be used as off-line audio edits. DirectX plug-ins for audio work in a similar fashion to VST, MAS, RTAS, etc., though they are not interchangeable with these formats. Furthermore, DirectX plug-ins cannot run on Macs. However, because DirectX is Microsoft’s plug-in architecture, one can be relatively certain that it won’t fade from popularity, and indeed it does have many programmers developing for it.