AdminXP.com: DirectX

DirectX

DirectX is an advanced suite of multimedia APIs (application programming interfaces) developed by Microsoft and built into Windows as the interface between HW and SW. The basic goal of DirectX is to enable sotware developers to write programs and drivers for HW without having to know computer configuration and hardware-specific code. Direct X simplifies creating of multimedia applications and increases their performance (the components access the HW directly and the capabilities of HW can be highly utilize).
The DirectX full-object interface is based on the COM architecture. The developers can access the DirectX components from C, C++, Visual Basic, but there also exist components for Delphi.
Now (8/2003) the 9.0b version is available that is not compatible with older systems as Windows 95, Windows NT 4.0 and lower.
MSDN - at the Microsoft´s MSDN sites you will find detailed information about DirectX. If you are a developer, it is recommended that you download the SDK kit (Software Development Kit) with code examples, documentation and other SW. Its disadvantage is its size of about 200MB.

Components:

DirectPlay - support of network communication via modem, Internet or local network for applications communicating among each other. DirectPlay is most often used for playing multiplayer games.
DirectInput - support of input devices, e. g. keyboard, mouse or classical game devices or force feedback devices.
DirectShow - support of digital media, HW acceleration of digital video decoding (DVD). Support of Microsoft TV Technologies. Support of multimedia streams. Support of ASF, MPEG, AVI, MP3.
DirectSound a DirectMusic - support for music and sound.
Direct3D - Interface for fast 3D graphics processing. Support of latest HW features of graphic cards and processors, providing more faithful and faster display on supported computers. It provides support for HW graphics acceleration (vertex shaders, stencil buffer)
DirectDraw - support for 2D graphics and animations. Many of its features are used either directly or indirectly by the Direct3D component of DirectX.

Notes to the Installation

Always use the latest version and you will get better graphic and audio features and higher performance. New versions usually bring improved drivers for input devices and support of multiplayer games. To fully utilize the newest versions of DirectX you need new drivers for the graphic and the sound cards that are able to use the new functions of DirectX.
Plus - there exist many reasons why to install DirectX: Some applications, games and drivers need it necessarily. Compatible HW and drivers used with the latest version of DirectX usually bring higher performance and more possibilities - better sound and new effects from the sound card and new display options from the graphic card.
Minus - there also exist reasons why not to install DirectX. DirectX used with older HW and drivers can endanger the functionality, the stability and the performance of the computer. For example, if you use the Directx9.0 with an older SiS VGA card, you will then have to install new drivers because the Internet Explorer when attempting to open it displays: "IEXPLORE caused an invalid page fault in module DDRAW.DLL". It similar to any other SW where a new version can eliminate some older errors of previous versions, but can also bring some new errors.

The Directx can be updated in several ways: 1. Use the Windows Update and download particular files from the Internet. 2. Use the installation pack (End-User Runtime) that runs the installation from the Internet. Similar to Windows Update. 3. Download the DirectX redistributable installation pack for developers and common users. After downloading you do not need to be connected to the Internet. You can also find it on some CDs with games or applications.
The installation packs can differ according to: 1. the type of operating system (Windows 9x/ME or Windows 2000/XP), 2. OS language version.
The information about installation is saved to the directx.log file in the %SYSTEMROOT% directory. This file contains detailed description of installed files and eventual discrepancies. This can be useful in case there are older files being installed - if there exist newer versions, these files will not be installed.

Uninstallation

DirectX cannot be unistalled. It is recommended that you create a "System Restore point" before installing DirectX, and if problems appear you can use the System restore tool to restore the operating system you had before the software was installed.
There also exist unofficial tools for unistalling DirectX. You can use them, but it is disputable and dangerous. These tools differ according to the operating system, the Directx version and used program.
After you have tried all possible ways, try to remove and reinstall the older version, edit registers and delete the old files. But this way is very dangerous because the problems can be even worse.
Some information about installed files and changes made you can find in the installation pack called "DirectX Redistributable for Software Developers" (you have to unpack the *.cab files).
In Windows XP the files are saved to: %SYSTEMROOT%\System32\DirectX, %SYSTEMROOT%\SYSTEM32\DirectX (*.dll libraries), %SYSTEMROOT%\System32\drivers (*.sys files), %SYSTEMROOT%\System32\DLLCache, %SYSTEMROOT%\INF, %SYSTEMROOT%\Driver Cache\i386, %SYSTEMROOT%\RegisteredPackages\
Registers: HKLM\Software\Microsoft\DirectX

Dxdiag.exe - DirectX Diagnostic Tool

You can run this tool by opening the Start menu - Run - enter dxdiag and confirm.
This is a very important tool for diagnosting the DirectX interface with all its components and drivers. Dxdiag gives you a lot of information, e. g. which version you are using and information about files and drivers - this helps you to find and solve problems. This program is able to test driver compatibility, display a lot of information, test the functionality of particular components. It also enables to activate/deactivate particular components or to set them up.