At German universities it is (in most cases) not necessary to register for a course before the semester. Students simply attend the first session which is announced in the Campo catalogue. They can decide to leave the course at any time (unless they have committed to an assignment such as a presentation, in which case they must talk to the lecturer in advance). In certain cases (lab courses, special seminars) the number of participants is limited and registration is necessary. This requirement will be announced in the online catalogue. In the absence of such an announcement, students hould simply join the first session of the course. Register is required for the exams, however. This is possible about six weeks after the start of the course.