X Window System is a network protocol and software system that displays on most Unix-like operating systems and OpenVMS. X Window System has been implemented on all major operating systems.
X Window System provides a standard kit and protocol to build a graphical user interface. These include moving windows on the screen as well as how to handle user input with the mouse and keyboard. X Window System does not write any special user interface, but leaves that to its client programs. Therefore, X-based environments vary in appearance too much. Using Desktop environment the end users faces a modern Unix desktop where the core programs of the X Window System barely comes in contact.
As an extension to X Window System, specifically a client-server system has been designed, which in additional to a transparent local network in use. X Window System is free software under the MIT license.
Technology of X Window System
The X server controls the input and output devices, such as pointing devices (eg mouse ), keyboard, monitor and graphics card. For this purpose it communicates with the operating system’s kernel, but in practice the kernel is bypassed.
The underlying concept of X Window System is an extension of the terminal concept of graphical user interfaces. The representation of X is a raster graphics based window manager, which provides various functions. This includes drawing and moving the window, the event-oriented handling of a pointing device such as a mouse, the inter-process communication and to some extent the administrative functions for print as well. So X Window System is a minimal system in which only primitives are provided.
The actual look and feel of the X Window System is therefore not determined by X, but by the X Window System manager that runs as a normal application simply as a client of the X server.
Other points on X Window System
Increased uniformity has also been pursued by several projects for X Window System. Approaches were for the creation of a desktop interface with a unified interface libraries for X Window System.