A set of multimedia programming interfaces from Microsoft for Windows. Windows developers program to the DirectX APIs, and the manufacturers of sound cards and display adapters write DirectX drivers to be included with their hardware. DirectX provides a high-level interface for accessing low-level functions "directly." It accesses the hardware abstraction layer in Windows (see HAL).
The first DirectX API was introduced in late 1995 to encourage game developers to move their software to Windows. Before DirectX, games for the PC were written in DOS in order to redraw the screen fast enough for realtime animation. To obtain the speed, gaming companies had to write drivers for a variety of display adapters, which was a development headache.
DirectX provides a single interface to write to, and DirectDraw and Direct3D provides calls to access the frame buffer and advanced features of the display adapter, which are not provided in the standard Windows GDI graphics interface. When DirectX was introduced, display adapter vendors were quick to develop DirectX drivers that would expose low-level functions of their hardware to the application. DirectX is also capable of emulating graphics functions in software that are not built into the hardware. This is known as the Hardware Emulation Layer (HEL).
To determine which version of DirectX is installed in your PC, select Run from the Start menu, type in dxdiag and click OK. Look under System Information for the DirectX Version number.