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What is X Windows?
X Windows is a "network transparent, platform independent" windowing system. What does that mean? It means basically
that you have a system which allows you to have various programs on your screen, some of which may not actually be
running on your local machine. You can run programs on remote machines and have them show up or display on your local
(or other) screen.
X Windows is one example of a server-client system, with a twist of sorts. In most such systems, the server is
some faraway machine and the client is the machine that accesses the resources on the server. In X, the server is on the
local machine - or "display" to be more exact - and the client can be anywhere, accessing the resources that the server
has to offer. Also, the clients and server tend to be on the same machine, while in some other examples, like NFS, the
server and clients are typically on different machines.
Before X came along every manufacturer had its own proprietary windowing system. For example PC windows, Apple Macintosh windows, Sun Windows and DEC windows.
These were all entirely different.
However, with X the programmer can now write a single application in a single language and run this program on different machines with little or no modifications.
Moreover, we can actually run programs on one machine and have the results displayed on one (or several) different machine's terminal.
The machine can be a similar computer (such as another Dec Workstation) or an entirely different machine altogether.
The possibilities are endless really.
For example in Fig. 1 below we have a ``local client'' and ``display server'' that run programs on a PC, a supercomputer and a large minicomputer all with windows being displayed on the same screen.
Fig. 1 Example of applications running across a network
This is because X is a network-based system. It has been common to have networks of the same computers for some time
(cf. departments network of PC's, MAC's, Sun's and Dec's Workstations).
It is relatively easy to get machines of the same type in this network configuration to talk to each other.
Now with X we can get different machines to talk to each other.
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