X Window System
The X Window System is a free, open-source windowing system for bitmap displays. It is basically a server for executing graphical commands; this allows the display hardware to be physically separated from the computation hardware. It is possible, for example, to connect to a remote system and run GUI programs on that system while displaying them locally.
- X Selections, Cut Buffers, and Kill Rings by Jamie Zawinski
- GNU Software (Free Software Foundation)