X Window System

X Window System
Original author(s)Project Athena
Developer(s)X.Org Foundation
Initial releaseJune 19, 1984 (1984-06-19)
Stable release
X11R7.7  / 6 June 2012
Operating systemUnix, Unix-like, MVS OpenVMS, DOS
PlatformCross-platform
PredecessorW Window System
TypeWindowing system
LicenseMIT License
Websitex.org

The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems.

X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at version 11 (hence "X11") since September 1987. The X.Org Foundation leads the X project, with the current reference implementation, X.Org Server, available as free and open-source software under the MIT License and similar permissive licenses.