1. Lower-division: 001–099; generally recommended for freshmen and sophomores. 2. Upper-division: 100–199; normally open only to students who have completed at least one lower-division course in the subject, or six quarters/four semesters of college work. Credit in special studies courses for undergraduates is limited to 5 units per quarter. 3. Graduate: 200-299; normally open only to students who have completed at least 18 upper-division quarter units basic to the subject matter of