Entering the Linux graphic environment (1)

This section describes the Linux graphical environment, including the concepts and features of X-Window, KDE, and GNOME. the following uses the red-flag Linux desktop version 4.0 as an example to describe the system configuration and application of the KDE desktop environment. The graphic environment facilitates the use and management of computer systems. Generally, you are familiar with the graphical interface of MSWindows. This section describes the Linux graphical environment, including the concepts and features of X-Window, KDE, and GNOME. the following uses the red-flag Linux desktop version 4.0 as an example to describe the system configuration and application of the KDE desktop environment.

The graphic environment facilitates the use and management of computer systems. Generally, everyone is familiar with the graphical interface of MS Windows. In fact, the Linux graphic system is not inferior. When you get familiar with their usage and features, you will feel comfortable. In Unix operating systems, the X-Window system is the most widely used Window-based user Gui, while the desktop systems commonly used in Linux systems are GNOME and KDE environments.

X-Window system

X-Window is a standard graphic interface for Unix and all Unix-like (including Linux) operating systems, sometimes called Xwindow or X. X-Window was developed in 1984 at the MIT research office for computer science. The X-Window system can be executed on many systems. Because it has nothing to do with the manufacturer, it is portable, the diversity of color processing and the transparency of network operations, making X an industrial standard. The current version of X is X11R6 (version 11th, sixth release ). In Linux, XFree86 is based on X11R6.

The architecture of X-Window consists of the customer/server model and X protocol.

1. X-Window customer/server model

In the X-Window system, X's service programs provide user programs with the ability to display output objects, including graphics and characters. X service programs are located between the customer program and the hardware, thus shielding the characteristics of specific hardware devices. the customer program only needs to send a display request to the service program, and the specific requirements displayed by the Service Program are translated, and pass it to the hardware device. Finally, the service program returns the event result to the user program.



Customer/server model

Shows the logical relationship between the customer program and the service program.

More specifically, the functions of customer programs and service programs are as follows:

(1) X service programs, also known as the display manager, are programs that control the actual display devices and input devices. It responds to client X requests and communicates directly with graphics devices. it is responsible for opening and closing windows and controlling bottom-layer operations such as fonts and colors. Each display device has only one X service program.

(2) X client programs are some applications that use the system window function and cannot directly affect windows or display. they can only request X service programs, and perform specific operations in the specified window through the services provided by the X service program. A typical "request" is usually: "output string 'hello' in the XYZ window", or "draw a straight line from A to B in red in the KDE window ".

You can use X client programs in the following ways: provided by the system (such as the clock program), provided by a third-party vendor, and compiled by yourself.

Typical X customer programs are as follows:

◆ Window manager is a customer process that determines the appearance of a window. It can change the window size or position, scale the window into an icon, and reschedule the position of the window in the stack. Linux supports multiple window managers, such as fvwm and Kdm.

◆ The desktop system is a customer process that controls the appearance of desktop icons and directories, as well as the content of desktop and directory menus, it also controls the effects of pressing and dragging on desktop icons, directories, and menus. The desktop system actually integrates the window manager and a series of tools. Currently, KDE and GNOME are the two main desktop systems in Linux. KDE uses Kdm as the window manager.

In addition, there are other X customer programs, such as xclock (a pointer or digital clock) and xclac (a calculator that can simulate scientific engineering computation.

2. X protocol

X-Window is a distributed application system. To enhance cross-platform portability, X's client/server model is built not on specific software and hardware resources, but on the X protocol. The X protocol is an abstract application service protocol that includes terminal input requests and screen output commands sent to X service programs, excluding access and control to underlying hardware. The X protocol is a way for X service programs to communicate with X client programs. X client sends a request to X service, and X service sends the status and other information through it. What actually controls the terminal is X service programs.

In addition, the X protocol is built on some common transmission protocols, including TCP/IP, IPX/SPX, and DECnet. Through these protocols, the customer and the server can easily communicate with each other.

In short, X is a network-based graphics engine that can process I/O operations on local graphics terminals while connecting to remote machines and running applications on them.

From the user's perspective, X-Window is composed of two different X parts: application interface and Window manager. 2.

Relationship between applications and window manager

(1) Application Interface
This interface controls the window running process of the application and the content displayed in the menu and dialog box.

(2) window manager
The window manager is an independent client program that controls window movement, size change, opening and closing.

Because the window manager does not belong to the application, it can be changed. Since all applications on a machine run under the control of a window manager, the window works in the same way at any specific time. In fact, X's window manager and specific X applications are all customer programs outside X's service programs.

GNOME desktop system

The desktop system determines the "View" of the operating system ". Currently, KDE and GNOME are the two main desktop systems used in Linux. The two environments have their own characteristics. you can choose to use them based on your preferences. For example, when installing Linux, you can select the KDE workstation environment or GNOME workstation environment.

GNOME is short for the GNU Network Object Model Environment. it is part of the GNU project and is a free software with fully open source code. GNOME is a user-friendly environment. in addition to excellent graphical environment functions, it also provides programming interfaces that allow developers to set the window manager according to their hobbies and needs. That is to say, GNOME and the window manager are independent of each other. It should be noted that the window manager and the desktop environment are two different concepts. for the same desktop environment (such as GNOME), different window managers (such as twm, fvwm, and Enlightenment) can be used ).

In Red Hat Linux, GNOME has been used as the default desktop manager. In this system, you can use the startx command to start the X-Window Server and GNOME. In fact, if you select a graphical logon interface when installing Red Hat Linux, the system starts them at the beginning and provides graphical logon prompts without using the startx command.

In GNOME, the menu functions are the same as those in Windows, and the usage is the same. However, the file systems used by Linux and Windows are completely different. Therefore, there is a big difference between the two in menu settings.

The GNOME Panel includes the following content: main system menu buttons, shortcut buttons for common applications (such as file manager, Netscape browser, X terminal simulation program, etc), some small programs (such as date and time display, virtual desktop paging tools, etc.), and the application display minimization button.

GNOME also provides powerful functions and software, including text processing, graphic editing, Web browsing, and multimedia tools. You can use the preceding main menu to run these programs, or enter the corresponding commands in the terminal simulation window to start them.

This article does not detail the features and applications of GNOME desktop systems. if you are interested, you can view the relevant information on your own.

Next we will introduce the concepts and features of the KDE desktop system, as well as the main components and functions of the KDE desktop system on the red-flag Linux Desktop 4.0 system, and the steps for configuring the display devices, printers, and screen saver.