Is there a non-X11 version of Prolog available?

[Simon Connah]

I've just been trying to install the SWI-Prolog port and it seems like  
it needs X11 installed to run. Is there a command line version of  
Prolog floating around at all? Or do I need to compile and install my  
own copy?

Cheers for any help.
Simon.

"I disapprove of what you say, but I'll defend to the death your right  
to say it." - Voltaire