Direct Draw

DirectDraw is the component of the Microsoft DirectXlibrary family of multi-media APIs. It is basically a game programming API.

It provides an abstraction of video surface(s) that should permit high-performance access and update of video displays that is portable across operating systems and environments (Microsoft operating systems and environments that is).

What it really was, is a way for Microsoft to finally drop DiskOperatingSystem from the game development picture.

I would say that goal was reached several years ago, though not really by DirectDraw. The major nail in the coffin came when IdSoftware started using OpenGl for its games, and then Direct3D really slammed it shut. Modern graphics cards support OpenGl and Direct3D acceleration natively.

BUT! how does it work??

http://msdn.microsoft.com has all the documentation you might want.