DirectX is a set of APIs designed to solve problems related to programming on Microsoft Windows. It is most widely used in writing computer games. The DirectX development kit for Microsoft Windows is available for free on the Microsoft site. Updated versions of DirectX are often bundled with game applications.
Almost all parts of the DirectX API are sets of COM-compatible objects.
DirectX is subdivided into:
DirectX Graphics, a set of interfaces previously (before version 8.0) divided into:
DirectDraw: a bitmap graphics output interface (its development has long since been discontinued);
Direct3D (D3D): an interface for outputting three-dimensional primitives.
DirectInput: an interface used to process data coming from the keyboard, mouse, joystick, and other game controllers.
DirectPlay: an interface for network game communication.
DirectSound: an interface for low-level sound (Wave format).
DirectMusic: An interface for playing music in Microsoft formats.
DirectShow: an interface used for audio and/or video input/output.
DirectX Instruments: a technology which allows to create and use software synthesizers based on the DirectX multimedia API. Unlike DX plug-ins, such programs can be fully controlled by MIDI and serve mainly for sound synthesis, not for processing. DXi technology was popular in 2001-2004, especially in Cakewalk software, but eventually lost the "format war" to Steinberg's VST technology.
DirectSetup: The part responsible for installing DirectX.
DirectX Media Objects: implements functional support for streaming objects (e.g., encoders/decoders).
Direct2D: an interface for rendering 2D graphics.