**Prior to September 1953, courses designated by letter rather than number (e.g., English A) were non-credit. Courses numbered 1 through 99 were primarily for undergraduate credit. Courses numbered 100 through 199 enrolled advanced undergraduate and some graduate students. Courses numbered 200 through 299 were for graduate students.
001-049 - Precollege and deficiency courses - no longer taught at Purdue University
050-099 - Nondegree courses (e.g., agriculture short courses) - no longer taught at Purdue University