X Window System

What Does X Window System Mean?

The X Window System (X11) is an open source, cross platform, client-server computer software system that provides a GUI in a distributed network environment.


Used primarily on Unix variants, X versions are also available for other operating systems. Features of the X window system include network transparency, the ability to link to different networks, and customizable graphical capabilities. The X window system was first developed in 1984, as part of project Athena, a collaboration between Stanford University and MIT. X.Org Foundation, an open group, manages the development and standardization of the X window system.

The X Window System is also known simply as X, X11 or X Windows.

Techopedia Explains X Window System

The client/server model in X system works in reverse to typical client/server model, where the client runs on the local machine and asks for services from the server. In X system, the server runs on the local machine and provides its display and services to the client programs. The client programs may be local or remotely exist over different networks, but appear transparently.

X is used in networks of interconnected mainframes, minicomputers, workstations, and X Terminals. X window system consists of a number of interacting components, including:

  • X server: Manages the display and input hardware. It captures command-based and graphics-based inputs from input hardware and passes it to the client application that requested it. It also receives inputs from the client applications and displays the output under guidance from windows manager. The only component that interacts with hardware is X server. This makes it easier to recode it as per the requirements of different hardware architectures.
  • Windows manager: Is the client application that manages client windows. It controls the general operations of the window system like geometry, appearance, coordinates, and graphical properties of X display. Window manager can change the size and position of windows on the display and reshuffle windows in a window stack.
  • X client: Is an application program that communicates with X server using X protocol. Xterm, Xclock, and Xcalc are examples of X clients. X manages its windows in a hierarchal structure. The shaded area that fills the entire screen is the root window. X client application windows are displayed on top of the root window and are often called the children of the root.

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Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…