backtrace or backtrace(N)

causes  the  parent goals and their arguments to be displayed starting with
the most recent goal.  If an argument is supplied, this instructs prolog to
limit  the  depth of this and future backtraces to N.  This Depth currently
defaults to 5.  Backtrace(0) is thus a means whereby users may turn off the
automatic backtrace generated after warnings.
