Friday, January 14, 2011

What is X Windows

X Windows was developed at Massachusetts Institute of Technology in 1984. The researcher at Massachusetts was attempting to devise a number of different graphical work stations, which were to be used by a large number of very different computers and operating systems. The X windows were designed in such a manner so that the communication between the displays and the computer would depend on the simple transmission of character based messages and not on any complex enclosed protocol.

Hence, X Windows could work on any network that was capable of carrying out simple character stream communication. There is large variety of X-based GUI systems, which are very much different from each-other. This is because X Windows do not follow any particular style or format. They only provide a means of producing GUI Systems.

The X system is based on a client server model. The application programs from the client, which require graphical display and input facilities. These facilities are provided by the servers.
The communication between client and server happens through messages, which are carried out in a standard protocol. The client and the server my exist as separate processes on one system or they may exist on separate computers and then linked over a network. X system is entirely machine-independent. The client application is not concerned with the internals of the ‘target’ display terminal it is using. The application concerns itself with a logical or virtual terminal. The X system must match with the requests made by the user on to time.
In GUI systems, a window manager takes care of the size, location, movement, etc. of windows. In X Windows, a windows manager functions as an ordinary client application program.
The facilities provide by X windows library are at a low level. Therefore, a considerable amount of coding is required to produce useful applications. The applications that are coded at this level do not always provide uniformity in the user interface.

Windows System based on PC’s
These days, there are two patterns of interface that are available in the market. One is the windows 3.1 version and the other is he Windows 95/ NT version. The w\two vary from each-other in quite a big way. The Windows 3.1 contains program manager and other program group facilities which are absent in Windows 95. The programs group allows the user to gather different programs together and organize them into logical sets. The same set-up is provided by the Start button in the case on Windows 95. On clicking at Start Button a pop-up containing may options shoots up on the screen.

� � o t x@ � pan style='font-size:7.5pt;font-family:"Verdana","sans-serif";mso-fareast-font-family: Verdana;mso-bidi-font-family:Verdana;color:black'>4.     The Kernel permits different processes to make use of the peripheral devices such as terminals, tape drives, disk drives and network devices as and when requested.
The services provided by the Kernel are absolutely transparent to the user. For instance, he Kernel formats the data present in a file for internal storage. 

However, it hides the internal format from user processes. Similarly, it makes a distinction between the regular file or a device but hides the distinction from user processes. Finally, the Kernel provided he services so that the user level processes can support the services they must provide. For instance, the Kernel provides the services that the shell requires to act as a command interpreter. Therefore, the Kernel allows the shell o read terminal input, to create pipes and redirect I/O. The computer users can also create private versions of the shell so that they can create an environment according to their own requirement without disturbing the other users.

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