Introduction to the Unix Cluster. Node: Anatomy

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X's Anatomy

The architecture of the X Window System is based on what's known as the client-server model. X consists of three parts:

  1. X Display Server - a program that keeps track of all input coming from input devices (such as the keyboard and mouse), input from any other clients that are running, and provides display capabilities. As the server receives information from a client, it updates the appropriate window on your screen. The display server keeps track of the hardware, may run on the same computer as a client or on an entirely different machine, and is the only part of X that must be machine-specific.
  2. Clients - application programs that perform specific tasks. These tasks can include keeping track of incoming mail (xbiff), terminal emulation (xterm), and even providing an on-line manual for X (xman). Very importantly, since clients need not be machine-specific (only the server interacts directly with the hardware), they can be ported easily from system to system.
  3. Window Manager - a program that handles negotiations between the different clients as they fight for screen space, colors, and sunlight. The window manager used at PPPL is twm, which is shipped with the standard release of X from MIT. It's the window manager that controls the moving of windows, converting windows to icons and back, and a large variety of other tasks. When you start up X-Windows, a file in your home directory known as `~/.twmrc' (See Customizing.) will be read to set up the look-and-feel of your screen.
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