The X Window System ( X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting with a mouse and keyboard. X does not mandate the user interface – this is handled by individual programs.

In computing, the X Window System (commonly: X11, or X) is a network-transparent windowing system for bitmap displays. This article details the protocols and technical structure of X11. In this example, the X server takes input from a keyboard and mouse and displays to a screen.

The X Window System, called X for short, is a network-based graphics window system that was developed at MIT in 1984. Several versions of X have been developed, the most recent of which is X Version 11 (X11), first released in 1987. X11 has been adopted as an industry-standard windowing system.