SWI-Prolog itself does not provide any   GUI  (Graphical User Interface)
capabilities. For building graphical  applications,   there  are roughly
speaking 3 options:

	# Embedding
	SWI-Prolog can be embedded in a C-program, and therefore any
	interface toolkit that can be accessed from C can be used this
	way.  

	# Using Tk/Tcl
	This provides a well understood portable GUI framework, where
	Prolog communicates to Tk/Tcl using I/O streams.

	# Using XPCE
	XPCE is a C-based library that can be used to add a
	dynamically typed object-oriented system to Prolog and
	other dynamically typed languages.  Features:

		* Efficient Object-system that can be extended using
	 	  Prolog-defined classes.
		* Many built-in classes offering high-level graphical
		  primitives.
		* Portable accross X11 (Unix) and Win32 (Windows 95, 98
	 	  and NT). Note that SWI-Prolog saved-states are
		  platform independent!
		* Runs on SWI-Prolog, Quintus and shortly SICStus 

	See http://www.swi.psy.uva.nl/projects/xpce/home.html