The X Window System is a network transparent window system which runs on a wide range of computing and graphics machines. The workstations available for use in the Edlab are running X11. The X window system supports overlapping subwindows. All the windows in an X server are arranged in a strict hierarchy. At the top of the hierarchy is a root window, which covers the entire display screen. The server distributes user input to and accepts output requests from various client programs located either on the same machine or elsewhere in your network. The number of programs that use X is quite large. Some commonly used programs are: a terminal emulator, xterm; access control programs, xauth and xhost ; user preference setting programs, xrdb, xset, and xmodmap; clocks xclock and oclock; utilities for listing information about fonts, windows, and displays, xlsfonts, xwininfo, xlsclients, xdpyinfo;