Often during your Prolog sessions you might find it useful to submit a query, edit it slightly, then resubmit it. For example, if you make a typing error in a query, you generally want to correct the error and resubmit the query, instead of retyping the entire query.
Everything you type during a Prolog session goes into an Emacs buffer, so it is easy to retrieve and copy lines you've already typed. Prolog then redisplays the query.