% this is a comment, % is like # in Perl
% All men are mortal
mortal(X) :-
    man(X).
% Socrates is a man.
man(socrates).

##</code><code>##

$ gprolog
GNU Prolog 1.2.8
By Daniel Diaz
Copyright (C) 1999-2001 Daniel Diaz
| ?- consult('socrates.pro').
compiling /home/Zaxo/socrates.pro for byte code...
/home/Zaxo/socrates.pro compiled, 6 lines read - 382 bytes written, 61 ms

yes
| ?- mortal(socrates).

yes
| ?- mortal(V).

V = socrates

yes
| ?- mortal(aristotle).

no
| ?- halt.
$