Xdm  manages a collection of X displays, which may be on the local host
or remote servers.  The design of xdm was guided by the needs of X ter-
minals  as well as The Open Group standard XDMCP, the X Display Manager
Control Protocol.  Xdm provides services similar to those  provided  by
init,  getty and login on character terminals: prompting for login name
and password, authenticating the user, and running a ``session.''