DirectX is a set of multimedia Application Programming Interfaces (API's) written by Microsoft. It is a collection of Dynamic Link Libraries (DLLs) that contain functions useful to a wide range of multimedia programmers, but are all almost entirely platform independent. This allows programmers access to fast graphics, sound, and input functions while not needing their apps to test for the capabilities of the computer on which their program is running. DirectX will evaluate these capabilities and if they are not present, DirectX may attempt (in many cases) to emulate the functions in software instead of hardware.

Windows NT shipped with DirectX 2.0. Upgrading to Windows NT 4.0 service pack 3.0 will install DirectX 3.0 will be installed.
However there are no higher versions of DirectX available for Windows NT. Installing Service Pack 4 or higher will install later versions of DirectPlay however.
Windows 98 shipped with DirectX 5.0.
Windows ME and Windows 2000 have DirectX version 7.0.
Windows XP has DirectX 8.0.
But anyway, If you are not sure if DirectX is installed on your computer, or do not know what version is installed, use the following instructions.
1. Click the Start button.
2. Choose Run.
3. In the Find dialog box, type dxdiag.exe
4. You can find DirectX version at the bottom of the "system Information" region.
5. Close the window.

Visit Microsoft's DirectX page at: http://www.microsoft.com/directx and download and double-click to run the install. Running this file will setup and install DirectX on your computer.

OpenGL is a programming interface mainly for 3D applications. It renders 3D objects to the screen, providing the same set of instructions on different computers and graphics adapters. Blenders whole interface and 3D output in the real-time and interactive 3D graphic is done by OpenGL.

Shareware gives you a great opportunity: try a game before you buy it. This means that you can evaluate the game for a period, or in a limited version, and if it convinces you enough to try it, you can buy the full (also called registered version).

The demo usually has some minor or major (that varies from game to game) differences from the full or registered version. For example, a puzzle game may let you play only the first five level in the demo, allowing you to play all of them in the full version. Usually the author explain clearly the limitation of the game in the game documentation.

Use the following links:
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