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      The KDE desktop allows you to place both application and file icons in a special area on the desktop. If you click an application icon, the Linux system starts the application. If you click a file icon, the KDE desktop attempts to determine what application to start to handle the file.

      The bar at the bottom of the desktop is called the Panel. The Panel consists of four parts:

      ● The K menu: Much like the Windows Start menu, the K menu contains links to start installed applications.

      ● Program shortcuts: These are quick links to start applications directly from the Panel.

      ● The taskbar: The taskbar shows icons for applications currently running on the desktop.

      ● Applets: These are small applications that have an icon in the Panel that often can change depending on information from the application.

      The Panel features are similar to what you would find in Windows. In addition to the desktop features, the KDE project has produced a wide assortment of applications that run in the KDE environment.

      The GNU Network Object Model Environment (GNOME) is another popular Linux desktop environment. First released in 1999, GNOME has become the default desktop environment for many Linux distributions. (However, the most popular is Red Hat Linux.)

      Although GNOME chose to depart from the standard Microsoft Windows look-and-feel, it incorporates many features that most Windows users are comfortable with:

      ● A desktop area for icons

      ● A panel area for showing running applications

      ● Drag-and-drop capabilities

Figure 1.4 shows the standard GNOME desktop used in the CentOS Linux distribution.

Figure 1.4 A GNOME desktop on a CentOS Linux system

      Not to be outdone by KDE, the GNOME developers have also produced a host of graphical applications that integrate with the GNOME desktop.

The Unity Desktop

      If you're using the Ubuntu Linux distribution, you'll notice that it's somewhat different from both the KDE and GNOME desktop environments. Canonical, the company responsible for developing Ubuntu, has decided to embark on its own Linux desktop environment, called Unity.

The Unity desktop gets its name from the goal of the project – to provide a single desktop experience for workstations, tablet devices, and mobile devices. The Unity desktop works the same whether you're running Ubuntu on a workstation or a mobile phone! Figure 1.5 shows an example of the Unity desktop in Ubuntu 14.04 LTS.

Figure 1.5 The Unity desktop on the Ubuntu Linux distribution

Other Desktops

      The downside to a graphical desktop environment is that it requires a fair amount of system resources to operate properly. In the early days of Linux, a hallmark and selling feature of Linux was its ability to operate on older, less powerful PCs that the newer Microsoft desktop products couldn't run on. However, with the popularity of KDE and GNOME desktops, this has changed, because it takes just as much memory to run a KDE or GNOME desktop as the latest Microsoft desktop environment.

      If you have an older PC, don't be discouraged. The Linux developers have banded together to take Linux back to its roots. They've created several low-memory–oriented graphical desktop applications that provide basic features that run perfectly fine on older PCs.

      Although these graphical desktops don't have a plethora of applications designed around them, they still run many basic graphical applications that support features such as word processing, spreadsheets, databases, drawing, and, of course, multimedia support.

Table 1.3 shows some of the smaller Linux graphical desktop environments that can be used on lower-powered PCs and laptops.

Table 1.3 Other Linux Graphical Desktops

These graphical desktop environments are not as fancy as the KDE and GNOME desktops, but they provide basic graphical functionality just fine. Figure 1.6 shows what the JWM desktop used in the Puppy Linux antiX distribution looks like.

Figure 1.6 The JWM desktop as seen in the Puppy Linux distribution

      If you are using an older PC, try a Linux distribution that uses one of these desktops and see what happens. You may be pleasantly surprised.

      Linux Distributions

      Now that you have seen the four main components required for a complete Linux system, you may be wondering how you are going to get them all put together to make a Linux system. Fortunately, other people have already done that for you.

      A complete Linux system package is called a distribution. Many different Linux distributions are available to meet just about any computing requirement you could have. Most distributions are customized for a specific user group, such as business users, multimedia enthusiasts, software developers, or average home users. Each customized distribution includes the software packages required to support specialized functions, such as audio- and video-editing software for multimedia enthusiasts, or compilers and integrated development environments (IDEs) for software developers.

      The different Linux distributions are often divided into three categories:

      ● Full core Linux distributions

      ● Specialized distributions

      ● LiveCD test distributions

      The following sections describe these different types of Linux distributions and show some examples of Linux distributions in each category.

Core Linux Distributions

A core Linux distribution contains a kernel, one or more graphical desktop environments, and just about every Linux application that is available, precompiled for the kernel. It provides one-stop shopping for a complete Linux installation. Table 1.4 shows some of the more popular core Linux distributions.

Table 1.4 Core Linux Distributions

      In the early days of Linux, a distribution was released as a set of floppy disks. You had to download groups of files and then copy them onto disks. It would usually take 20 or more disks to make an entire

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