High Quality Content by WIKIPEDIA articles! XDM (in full, the X Window Display Manager) is the default display manager for the X Window System. It is a bare-bones X display manager. It was introduced with X11 Release 3 in October 1988, to support the standalone X terminals that were just coming onto the market. It was written by Keith Packard. Because of its lack of user-friendliness, users of GNOME, KDE, Enlightenment or Window Maker tend to use GDM, KDM, Entrance or wdm instead of XDM.