To be able to take some courses, a more basic course –which is called prerequisite course– should be taken previously. If it is specified in the course catalog that a course has a prerequisite, the prerequisite must be passed successfully (AU grade is not considered as passing the course). The prerequisite courses should be taken primarily as otherwise this may cause in lengthening of education period. You can consult respective Dean’s Office and KUSIS for the courses offered in a particular semester.