Chapter 3 introduced Linux's graphical desktops, and many subsequent chapters showed you the spiffy and powerful tools you could run on them. Rarely do you have to deal with the underpinnings that make all this possible, but occasionally your screen resolution isn't as good as it could be, or you have trouble getting graphics to start. At these times you notice that error messages are referring to an X server or to various files and libraries with an x in them.
Basically, the X Window System encompasses all the software that lets a CPU understand a video card and get graphics to appear on a monitor. X goes far beyond this, though: it provides an interface of almost unlimited flexibility to let programs display graphics, interact with the user, and exchange data with other graphical programs. KDE and GNOME are both sets of libraries and tools that run on X. In this chapter, we tell you how to install and configure the X Window System in case it was not done by your distribution properly.