SB-Prolog also provides a facility for low-level tracing of execution. This can be activated by invoking the simulator with the -T option, or through the predicate $trace/0. $trace/0 (L) It causes trace information to be printed out at every call (including those to system trap handlers). The volume of such trace information can very become large very quickly, so this method of tracing is not recommended in general.
Low-level tracing may be turned off using the predicate untrace/0. $untrace/0 (L)