X is not a monolithic application. It consists of
a number of parts:
- X11R6.6 -- protocols, libraries (e.g. Xlib, Xt), sample code and programs
- XFree86 4.2.??? -- drivers, modifications for PC-based hardware
- Window Managers -- Fvwm, AfterStep, WindowMaker, Sawmill, Enlightenment, Kwin
- Toolkits/Widget Sets
- Applications -- Gnumeric, Netscape, Mozilla, xterm
- Environment -- combination of Toolkit, Window Manager and Applications.