All students must register for this 2 unit course only during semesters that a student is a Teaching Assistant (TA). The 2 units received for this course are not counted toward M.S. or Ph.D. requirements. Assignments are made by the department office and announced at the beginning of each semester. The duties generally consist of grading problem sets and holding office hours. An instructor may ask a TA to fill-in for a lecture if the instructor is unavoidably away from campus during the class period - this might occur for no more than a couple lectures for a given class. This is a course requirement for graduation and must be taken by all students; it is in no way linked to a student's source of financial support. The requirement of five hours per week lasts for three semesters, and consists primarily of grading papers and leading recitation sessions. A student may volunteer to assist in teaching after his or her three-semester requirement has been fulfilled. Many students find this aspect of their education enjoyable and satisfying. The two-unit course, 42-799, is the vehicle for these assignments. All students must register for this course during each semester of full-time study. To re-emphasize, this course is a requirement for graduation and must be taken by all students and is in no way linked to a student's source of financial support.