X11 is perhaps most widely seen now as a graphical system for Linux, but rendering graphical user interfaces is not X Window's primary talent. Where it shines and has some amazing facilities is as a truly network-aware environment for applications.

So, if you are using Linux remotely you don't have to miss out on your X programs.

Server, Client, Window Manager

The main components of X Window are the X Server, the Window Manager and the client programs. If we ignore the networked aspect of X11, then these components run locally. If you only use X11 like this, though, you are missing out, as any X components can run anywhere on the Internet! The client server architecture of X makes this not only possible but quite easy.

It is worth mentioning in passing that the terminology of the client-server part of X11 equation can often seem tricky to grasp. Part of the reason that this terminology may seem odd is that X11 was one of the earliest systems to be implemented as client server. Its old age ( it recently had its fifteenth birthday) means that most of the problems of X have been ironed out. Normally the part of a client-server system nearest to you will be the client. However, in X11 the part that interacts with the user is known as the X Server! The clients can run anywhere and in practice this means that they often are remote, as we will see below. This is the opposite way round to other client server systems, like the WWW, e.g. Web browsers are usually called clients and they are local in relation to you, the user. With WWW systems the server part is remote. Try and bear this in mind when reading about X11; the server is the user interface hardware, but the clients can be distributed.

The Window Manager is a special type of client that controls window placement. Like all clients, though, it can run anyplace. There are many different Window Managers available for X; see elsewhere on Linuxplanet for a run-down of the Pros and Cons of different window managers

Next: Configuring the Server and client »