I've noticed that while in English you wouldn't talk about the General de Gaulle, in French you can talk about le général de Gaulle, le commissaire Maigret etc. Is this obligatory or is it a formal register?
Thanks! If it's mandatory, I must ask further: apparently it's also used before professeur, docteur and so on (I googled "le professeur Jacques" etc.): does this mean that the professeur, docteur etc. is the person's title (in a way, a sort of rank), rather than occupation? So that e.g. "docteur XY" could be somebody curing people without any formal medical education, while "le docteur YX" could be somebody with the title but working in an altogether different field?
We actually always say "Le docteur XY", unless you're addressing the person: "Docteur Martin, pourriez-vous m'aider, s'il vous plait ?". By contrast, we never use an article with Monsieur, Madame, Mademoiselle and Maître (maître is a title given to lawyers: "Maître Dupont, l'avocat de madame Dubois, a déclaré que...").
Of course, there are exceptions as mentionned by Oddmania (direct or indirect styles), but a rule seems to me rather general: French does not like nouns without article ; -)
(a crude formulation, I agree...).