X Windows clients and servers

In X windows clients and servers are used to handle input and display the output on the screen window.

X-Clients

X-client display output on a separate window on the display. An X client is an application program that performs certain tasks, communicating with the X server using the X Protocol. The operations performed within a window can vary greatly, depending on the type of program running. Some windows wait for input from the user and function as terminals, for example, calculators or graphics applications. Other windows simply display information, such as the time of day or the system load.

X-client application windows are displayed on top of the root window. X treats windows as a hierarchy, with the root as the origin or parent, of the application windows displayed on it. Conversely, the application windows are called”children of the root window”. But the hierarchy goes further. Not only is the client window itself a child which itself is a window. the root window, but it also can have children of its own; for example, a drop-down menu, which itself is a window.

A few of the most commonly used clients are described below:

The Xterm Client

The Xterm client is probably the most commonly used X – client. It simply provides a terminal window to the machine on which the Xterm client is running. For example, if the xterm is running on a Sun, a normal unix shell will appear within the Xterm window

The xterm client partially, emulates a VT-100 series termial- the emulation supports most of the VT 102 features apart from double height and double width character. The terminal settings can be altered by pressing the control key and any of the 3 mouse buttons inside the xterm window. The 3 menus which POP up allow you to after many of the properties of the term.

The Xman Client

xman is also a useful client. xman is a graphical interface to the unix manual pages. In it by using the mouse, it is possible to display any of the hundreds of pages of information available. It is very useful in all the x-clients.

The Xbiff Client

xbiff client is use for notify when new mail is arrive. In it, a picture of an american style mailbox is use, and whenever a new mail is arrive, the flag on the side of the box will be raised.

The Xedit Client

xedit is a simple text editor. It does not have the power of editors such as vi or emacs, but in some circumstances, this has a distinct advantage, as it means that there are very few commands to remember. This makes it a very easy editor to use.

The Xclock Client

It display an analogue clock on your screen.

The X-server

The X-server program must be able to handle not only the application’s output but its input as well. The X – server manages the display hardware. The server captures input events from the user via keyboard, mouse, and other input devices and after that passes the information to a client application that has requested it. It also receives requests from the application to perform some graphical action.

For example, if we use our mouse to move a window on the screen, the X-server passes the information to the window manager, which responds by telling the server where to reposition the window and the X-server performs the action. If the client is a calculator, such as xcalc, it might request that digits be displayed into the window as the user clicks on buttons to enter a number.

It is always the server that interacts with the hardware. Thus, only the server software has to be hardware-specific. In fact, only the parts of the server that actually interact with the hardware need to be rewritten for X to be ported to new systems or to be usable with a new terminal or a new type of input device ; for example: as long as the X-clients are written to use the X Protocol, they can run on any system and communicate with the X-server.