Each course in the curriculum is defined by an alphabetical prefix and a 3-digit number. The 3-digit number indicates the level of study: 100- and 200-level courses are lower division; 300- and 400-level courses are upper division; 500-, 600- and 700- level courses are graduate courses. A number of courses have no prerequisites. These are open to all interested students. All others are open to all students who meet the prerequisites.