Here is a sample session. We use $ for the Unix shell prompt, and ?- for the Prolog shell prompt.
$ rlwrap swipl
130f@ieng6-202]:~:501$ swipl
Welcome to SWI-Prolog (Multi-threaded, 32 bits, Version 5.10.5)
Copyright (c) 1990-2011 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.
For help, use ?- help(Topic). or ?- apropos(Word).
?- X = cat.
X = cat.
?- X = Y.
X = Y.
?- halt.To load a program lec-prolog.pl from disk use the consult command like so:
?- consult('lec-prolog.pl').
% foo.pl compiled 0.00 sec, 10,640 bytes
true.
?- parent(albert, z).
false.
?- parent(albert, Z).
Z = felix ;
Z = dana.
?- parent(Z, dana).
Z = albert ;
false.