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 XDM's minimalism, most desktop environments tend to use later, more sophisticated display managers.
XDM or xdm or similar can refer to: