There is little point, these days, in writing a large and introduction to Prolog programming. Most technical bookshops will sell a range of introductory Prolog texts, most of which repeat (in various different styles) the same basic material. So the first thing to do if you are serious about learning Prolog is stop reading these notes; go down to your nearest technical bookshop and find an introductory text which suits you. The next thing to do is to get access to one of the standard dialects of Prolog. There are umpteen different implementations of Prolog systems and each has its own idiosyncracies. Fortunately, there is a core set of notation which tends to be provided by most Prolog systems and there is now an ISO standard for the language. We try to stick to this core in order to avoid portability problems, but give no guarantees of portability.