Xbox
Released in 2001, the Xbox control pad was the first controller made for the original Xbox. The Xbox controller features two analog sticks, a pressure-sensitive directional pad, two analog triggers, a Back button, a Start button, two accessory slots and six 8-bit analog action buttons (A/Green, B/Red, X/Blue, Y/Yellow, and Black and White buttons). The standard Xbox controller (originally nicknamed the "Fatty" and later the "Duke") was originally the controller bundled with Xbox systems for all territories except Japan.
DirectInput
XInput, an API for "next generation" controllers, was introduced in December 2005 alongside the launch of the Xbox 360. This instruction set provided full support for Xbox 360 controllers in Windows XP SP1 and subsequent operating systems, and is described by Microsoft as being easier to program for and requiring less setup than DirectInput. XInput is compatible with DirectX version 9 and later.