4.1. What is the X Window System?   

The X Window System permits a user sitting at one machine to run programs on a remote machine but still interact with the program locally. X is in effect one way for different systems to interface with each other. It will let a program run on one computer and yet display its output on another computer, even when the other computer is of a different species. The program will display its output on the local machine, accept keyboard and mouse input from the local machine, but will execute on the CPU of the remote machine.

The local machine will typically be a workstation, Macintosh, PC or a dedicated X terminal. The remote machine may be a workstation, a minicomputer (eg VAX) , a mainframe or even a super computer (eg Cray). It is also possible (and highly likely) that the local machine and the remote machine are in fact the same machine. With the X Window System you have the flexibility to make this choice, without having to change the program!

In summary, X is a distributed, intelligent, device independent, operating

system independent, windowing system.