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Computer Science 61 and E61
Systems Programming and Machine Organization
Fall 2015


This page contains information specific to Extension School students. Extension students are also subject to the course policies for all students.

Link to AdobeConnect classroom (for web conferences)


Prerequisites for this course for Extension students are CSCI E-52, CSCI E-26, or experience programming in C.

Note: This course requires programming in C. You should deeply understand C pointers and arrays before taking this course. Ideally you should already have experience programming in C. If you have not previously programmed in C but know another procedural language, such as Java, you will likely be able to quickly learn what you need. See the resources page for pointers to material for learning C. Talk to the instructor if you are unsure whether you are sufficiently prepared for CS 61.

Add/Drop deadlines

Please see the Extension School calendar for details of registration dates, add/drop dates, etc. Note that the important drop/withdrawal deadlines are September 8 -- full tuition refund, September 15 -- half tuition refund, and November 27 -- withdrawal.


This course is being taught in a flipped style. That means that material traditionally presented in lecture will be available to you before class. You are expected to review the material before "class," and we then spend class time working in small groups solving problems. Extension students are welcome to physically attend lectures, but we will also hold live web conference sessions where instructors will walk you through the exercises just as we do in class. You are strongly encouraged to attend these sessions. However, we do understand that it is not always possible and we will endeavor to make it possible for you to do the exercises outside these sessions. Again, we encourage you to work on the problems with other classmates, using some form of online conferencing -- a significant part of the learning will happen from joint problem solving and explaining things to each other.

Web conferences will be held Tuesday 7:00 - 8:30 PM EST and Thursday 8:30 - 10:00 PM EST. Attend web conferences here.

Please review the material here to make sure that you have everything set up for the web conferences. If you have never used an Adobe Connect web conference, we strongly encourage you to attend one of the training sessions.

As we are asking a lot of you in attending these web conferences, sections will be optional -- we will have a recorded section that you can watch live if you wish, but that will be available for offline viewing as well. (See below.) If you would like to attend a section in-person other than the recorded one, please contact the course staff at cs61-staff@g.harvard.edu.

Finally, Professor Seltzer will hold online office hours on the weekend (the exact time is TBD) -- this will provide a great opportunity for you to get questions answered in real time.

Lecture and Section videos

Recorded section videos will typically be available a day or two following the live section. We will have videos from class time available, one per week, at the end of the week.

Videos from lecture: YouTube Video Channel

Section videos: Virtual Classroom

Office Hours

Office hours for Extension School students will be held over Skype weekly on Wednesdays from 9:00-10:00AM EDT and again from 7:00-9:00 PM EST. Additionally, students can make arrangements to meet on Skype. The CS61 staff Skype username is "cs61staff" (lowercase). Professor Seltzer will hold online office hours in the web conference room on Saturdays from 10:00 AM - Noon (EST).


Assignments for Extension students are the same as for College students, and the same policies apply regarding late days, grading, etc.

One exception is that assignments for Extension students are due exactly 24 hours after the College student deadline (i.e., college deadlines are Friday nights; extension deadlines are Saturday nights). This only applies to assignments, and not forms that we may need you to fill out or exams.

Like other students in the course, Extension students may work in pairs for the assignments that allow this. Extension students may work with other Extension students or with College students, although we find that Extension pairs work best (because Extension students tend to have similar schedules). Please contact the course staff if you would like to work with a partner but are having trouble finding someone.

Course staff and sections

Course staff information

All students, including extension school students, should use Piazza (or, alternately, cs61-staff@g.harvard.edu) for requests.


Extension students sit the same exams as College students: a midterm exam in mid-October, and a final exam in mid- to late December. Exam dates will be posted on the schedule. We will provide proctors during a several-hour window in the evening for those in the Boston area. For those not attending the exam in person, you must sit for the exam, with a proctor arranged through the Extension School, within a 24 hour window starting on the exam day at the time of the college exam.

Please refer to the Extension School pages on exams for more information on Extension School exam requirements and proctoring.


Extension students are given the same work as College students, but graded on a different curve (College student marks won’t affect Extension student marks, and vice versa).