LINUX : CHAPTER 6 THE X-WINDOWS SYSTEM

SERVER & CLIENT RELATIONSHIP

While the X-window system was being developed, people were already working with several type of graphical user interface.

If an application had to be developed, it was necessary that we developed different versions of the apk. for different interface available in the market.

The X-window system can be divided into a client & a server.

We know that a client is a program that interact with the user and request services from the server program and that server do not interact with the user.

COMPONENTS OF X-WINDOW SYSTEM

It consists of three main components these are -

1. X - SERVER

It is responsible for handling and controlling the video display & interface through the keyboard and mouse. It accept the request send by the client program.

2. X - CLIENT

This program is the apk. program. X - window system is not limited to anyone client or anyone server, many combinations are possible.

3.  The communication link between X - server & X - Client can be some inter-process communication mechanism.

It client & server are running on different machines. The communication link will be implemented over a network.

X - ORG. SERVER DESIGN

X - ORG. functions in a client server model, an X - server communicates with various program. The server accept request for graphical output & send back user input. The server may function as - 

1. An apk. that display contents of a window of another display system.

2. A system program that controls the video output of a PC.

3. A dedicated piece of hardware.

X - ORG. CLIENT SERVER DEVELOPMENT MODAL

The X - ORG. follows the reverse client server architecture. The users terminal is the server & the apk. are the clients.

The X - Server receives input from the keyboard and mouse and display the result in the screen.

A web- browser & a terminal run on the users work station. The apk. run on a remote client which is control & monitor from the users machine.

The use an X-Client program on a remote machine, the user has to do the following -

1. On the local machine open a terminal window.

2. Use telnet to connect the remote machine.

3. Request local display, input service to the remote machine.

RUN - LEVELS

It refers to a mode of operation in Linux system. It determines the configuration of the machine after boot.

Their are seven run levels no. from zero to six. A run level is executed in an either manner or not sequentially that is either run level two or three or four is executed not two then three then four.

When a computer enters run level zero, and when it enters run level six it removes. The intermediate run level one to five differ in terms of which drives are mounted, and which network services are started.

TYPICAL LINUX RUN LEVELS

In the most Linux distributions, the run levels are defined as following -

LINUX RUN LEVELS

 

ROLE OF WINDOW MANAGER

The look and feel of X programs is determine not by the X-Server but by it a different product called GUI. This GUI is known as the window manager. Window Manager is a client program that has the following role to play -

1. Controlling how different window should appear on the screen.

2. Determining how users can interact through the windows.

3. Determine how windows can be created and destroyed.

4. Determining the mechanism for moving windows around the            screen or changing their appearance.

   

• Rename PNB folder to SBI.
• Copy all files of current A/c to Saving A/c.
• Delete all files of customers details of current A/c
• Show the directories or files of the root folder.
• Copy all the contents of DICS file to DICS 1 file.
• Count the no. of lines in a file in customers details of Saving A/c.

Commands

• $ mv PNB SBI
• $ cp * current A/c Saving A/c
• $ rm customer details current A/c
• $ ls PNB
• $ cat DICS > DICS1
• $ wc -l customer details Saving A/c

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