The Direct X software development kit (SDK) consists of runtime libraries in redistributable binary form, along with accompanying documentation and headers for use in coding.
Originally, the runtimes were only installed by games or explicitly by the user.
The API was developed jointly between Microsoft and Nvidia, which developed the custom graphics hardware used by the original Xbox.
The Xbox API was similar to Direct X version 8.1, but is non-updateable like other console technologies.
Eisler wrote about the frenzy to build Direct X 1 through 5 in his blog.
Direct X 2.0 became a component of Windows itself with the releases of Windows 95 OSR2 and Windows NT 4.0 in mid-1996.
Direct3D was intended to be a Microsoft controlled alternative to Open GL, focused initially on game use.
Windows 98 and Windows NT 4.0 both shipped with Direct X, as has every version of Windows released since. While the runtimes are proprietary, closed-source software, source code is provided for most of the SDK samples.If a developer chose to use Open GL 3D graphics API, the other APIs of Direct X are often combined with Open GL in computer games because Open GL does not include all of Direct X's functionality (such as sound or joystick support).In a console-specific version, Direct X was used as a basis for Microsoft's Xbox, Xbox 360 and Xbox One console API.Direct3D is also used by other software applications for visualization and graphics tasks such as CAD/CAM engineering.As Direct3D is the most widely publicized component of Direct X, it is common to see the names "Direct X" and "Direct3D" used interchangeably.The Direct X team faced the challenging task of testing each Direct X release against an array of computer hardware and software.A variety of different graphics cards, audio cards, motherboards, CPUs, input devices, games, and other multimedia applications were tested with each beta and final release.At that point a "battle" began between supporters of the cross-platform Open GL and the Windows-only Direct3D.Incidentally, Open GL was supported at Microsoft by the Direct X team.Starting with the release of Windows 8 Developer Preview, Direct X SDK has been integrated into Windows SDK.In late 1994, Microsoft was ready to release Windows 95, its next operating system.