X Window System

In computing, the X Window System (commonly X11 or X) is a networking and display protocol which provides windowing on bitmap displays. It provides the standard toolkit and protocol to build graphical user interfaces (GUIs) on Unix-like operating systems and OpenVMS, and is supported by almost all other modern operating systems.

X provides the basic framework, or primitives, for building GUI environments: drawing and moving windows on the screen and interacting with a mouse and/or keyboard. X does not mandate the user interface — individual client programs handle this. As such, the visual styling of X-based environments varies greatly; different programs may present radically different interfaces.

X features network transparency: the machine where application programs (the client applications) run can differ from the user's local machine (the display server).

X originated at MIT in 1984. The current protocol version, X11, appeared in September 1987. The X.Org Foundation leads the X project, with the current reference implementation, version 11 release 7.2, available as free software under the MIT License and similar permissive licenses . Release 7.2 was originally planned to be released on November 24, 2006, later pushed back until December 11 2006, and not actually released until February 15 2007.