The PDT lets you use all the built-in tracing facilities of SWI-Prolog. The SWI-Prolog tracer is invoked by calling trace before the goal you want to trace. For instance, if you want to trace the execution of p(X,Y,Z) you call:

?- trace, p(X,Y,Z).

What you get as a result of such a call depends on the enabled tracing mode:

GUI Tracer (recommended, enabled by default)	Console Tracing

A note to Mac users To use the GUI tracer you need to have a X11 server running. On the Mac you need to start it explicitly, it is not on by default.

The GUI tracer is enabled / disabled by using the menu in the Prolog Console Toolbar.

Alternatively, the GUI tracer is enabled / disabled by typing guitracer / noguitracer in the Prolog Console: