Introduction

In computing, the X Window System (commonly X11 or X) is a windowing system that implements the X display protocol and provides windowing on bitmap displays. It provides the standard toolkit and protocol with which to build graphical user interfaces (GUIs) on most Unix-like operating systems and OpenVMS, and has been ported to many other contemporary general purpose operating systems.

References

1. http://en.wikipedia.org/wiki/X_Window_System