Princeton University
Computer Science Department

Computer Science 217
Introduction to Programming Systems

Christopher Moretti

Fall 2020

General Information | Schedule | Assignments | Announcements | Policies


Yes, this page is long, but it is important to read it in its entirety, otherwise you might act against course policies, which could have serious consequences.


We encourage you to listen attentively to the lectures, but also participate actively by asking helpful questions occasionally, answering questions occasionally, and so forth. (You have the opportunity to do so in the Watch Party office hours or the Ed thread for each lecture.)

Some of the material covered in lectures is not covered in the textbooks or precepts. Some exam questions may reward your lecture attendance.


We encourage you to attend the precepts. We also encourage you to participate actively in the precepts by listening attentively and expressively, asking helpful questions occasionally, answering questions occasionally, and so forth. Your precept attendance and participation are important to your success in the course. They also are important to the success of the course as a whole, and so will be components of your participation grade.

Some of the material covered in precepts is not covered in the textbooks or lectures.

You should attend your precept, that is, the precept for which you are registered in Princeton's TigerHub system.

Concerning attending another precept instead of your precept:

Generally it is not acceptable to attend another precept instead of your precept consistently. Your participation grade will suffer if you do not participate in your precept. However, it is acceptable to attend another precept instead of your precept occasionally if a conflict with your precept arises. (Indeed you should do so.) In that case, as soon as you become aware of the conflict, send e-mail to your preceptor and the other preceptor. Note that this mechanism is intended to address occasional conflicts; it does not provide license to attend precepts other than your precept on a regular basis.

Concerning attending another precept in addition to your precept:

Generally it is not acceptable to attend another precept in addition to your precept consistently. After all, if even a small fraction of the course's students did that routinely, then some precepts would be very large routinely. Precepts containing a large number of students are less effective than those containing a small number. However, it could be acceptable to attend another precept in addition to your own occasionally. In that case, send e-mail to your preceptor and the other preceptor the day before the precept, asking permission to attend. The preceptors then will make the decision.

Electronic Communication

These are the course's policies concerning electronic communication:

In the context of electronic communication, the phrase "any of your assignment solution" includes:

Assignment Conduct

The policies described in this section supplement University academic regulations. This course has course policies that go beyond University policies on academic conduct. Princeton's Rights, Rules, Responsibilities handbook asserts:

The only adequate defense for a student accused of an academic violation is that the work in question does not, in fact, constitute a violation. Neither the defense that the student was ignorant of the regulations concerning academic violations nor the defense that the student was under pressure at the time the violation was committed is considered an adequate defense.

If the course staff suspects that you have violated course policies concerning assignment conduct, then the course staff will investigate, make an appropriate determination, and apply a penalty. The default penalty is a 0 grade for the assignment on which the violation took place, but the course's instructor of record may adjust this penalty to as little as 0 credit for the portion of the assignment on which the violation took place, or to as much as an F in the course for a particularly severe violation. Additionally, if the course staff determines that you may have violated University policies, you will also be referred to the Committee on Discipline, Honor Committee, or other relevant body. These bodies may impose additional penalties. Note that it is possible to violate the course policy without violating University policies. In those cases, the ruling on University policy does not override any penalty for the course policy violation.

This course takes policy violations seriously, and so does the University. According to the University document Academic Integrity at Princeton, plagiarism can occur when as little as "one key word" is used without citation (see

If you have any questions about these matters, please consult a course staff member.

Concerning receiving help:

In short: To help you compose an assignment solution you may use only the authorized sources of information that are listed below, may consult with other people only via the course's Ed forum or via interactions that might legitimately (see explanation below) appear on the course's Ed forum, and must declare your sources in your readme file for the assignment. Using impermissible sources is a violation of course policy. Failure to cite sources is also a violation of University policy. While citing an impermissible source may avert plagiarism, it does not avoid the restrictions imposed by course policy.

To help you compose your assignment solutions you may use:

To help you compose your assignment solutions you may use only the sources of information listed above. For example, you may not use:

There are three exceptions to those policies:

Examining and/or copying someone else's code is an egregious violation of course policies and perhaps University policy. Copying and transforming someone else's code (by rearranging independent code, renaming variables, rewording comments, etc.) is just as egregious (and perhaps moreso, because it displays intent to deceive). Some inexperienced programmers have the misconception that detecting such violations is difficult; actually it is quite easy. Not only do such violations quickly identify themselves during the grading process, but also we can (and do) use software packages, such as Alex Aiken's renowned MOSS software, for automated help.

There is one exception to that code-copying-and-transforming policy. You may adapt code from the course materials provided that you explain what code you use, and cite its source in your readme file.

For each assignment you must declare, in your readme file, the authorized sources of information that you used to compose your assignment solution.

For each assignment you also must declare in your readme file the unauthorized sources of information and help that you used to compose your assignment solution and explain in detail any violation of course policy and University policy. The penalty for course policy violations will depend on the level of severity and the level of clarity in these explanations. Declaring that "(So-and-so) offered a key insight about the challenge portion" is less severe than "I copied the majority of this assignment from (So-and-so)". Declarations such as "I got help from a friend" are less clear and detailed than either of the previous examples, to the extent that they may not even constitute a viable citation, risking rising to a violation of both course and University policies.

Concerning providing help:

In short: You may help other students with assignments only via the course's Ed forum or interactions that might legitimately appear on the course's Ed forum, and you may not share your assignment solutions with anyone, ever, in any form.

You may not provide assignment-related help to another student in any form (verbally, computer files, e-mail messages, pencil/pen on paper, marker on white board, chalk on black board, etc.) at any level of detail (code, pseudo-code, flow charts, outlines, diagrams, natural language prose, etc.) at any time (before or while the student works on the assignment solution). That policy holds even after the due date/time of the assignment, and even after the course is finished. That is, you may not provide assignment-related help to students who take the course in future semesters.

There are four exceptions to those policies:

Sharing your assignment-related code/comments with another student is an especially egregious violation of course policies. Sharing your code/comments in digital form is even more egregious. Do not give hard copy of your work to anyone. Do not e-mail your work to anyone. Do not make your work available to anyone via the web.

Any source code repositories containing your work should be configured to be private, with no additional collaborators (with the exception of a partner for partnered assignments detailed below). When you pull a local working copy of a repository onto the armlab cluster (or any shared computing environment), use the filesystem's permissions to make your files private. You can create a private directory in the CS armlab filesystem by issuing commands similar to these in a shell logged into that cluster:

mkdir cos217
chmod 700 cos217

Similarly, you should ensure security of your personal computer, external hard drive or flash drive containing your work, etc. with a password and enable password protection whenever you leave it unattended.

Remember that you are responsible for keeping your assignment-related work away from prying eyes. If someone else copies your work, we have no way of knowing the circumstances. In that case we will refer the matter to the Committee on Discipline, and the Committee will investigate.

Concerning retaking COS 217:

If you took COS 217 (or part of it) during a previous semester, then you may use your work on assignments from that previous semester. However you may not use:

Concerning partnered assignments:

Some of the assignments will allow you to work with 1 partner. You may choose to work alone on some or all of the partnered assignments (though we don't recommend it), to work with the same partner on multiple assignments, or to switch partners between assignments, as you see fit.

Only one partner should submit the final version of the assignment. If the other partner has submitted along the way before the final version, that partner must retract those submited files using the unsubmit command. Failing to do so may waste grader time and resources and incur a penalty.

You must "declare" your partnership upon submission. To do so, as part of your final submission create and submit a file called $NETID.partner (where $NETID is the armlab login of the partner who is not issuing the submit command). Thus, if you are submitting assignment X for you and your partner joestu, joestu would issue no submit commands and you would issue these commands in addition to the other file submissions:

touch joestu.partner
submit X joestu.partner

Both partners for an assignment will receive the same grade on that assignment. Following from this, both partners must use the same number of late days. (See the full lateness policy below.)

As far as fairness and joint effort are concerned, the overarching principle is that each partner is responsible for equally sharing in all elements of the assignment. This precludes "divide and conquer" approaches to the assignment. It also requires introspection to prevent a situation in which you are "carrying" your partner or allowing yourself to be "carried".

We believe that the COS 126 partner collaboration policy is a good guideline with lots of good advice. COS 217 allows more leeway in terms of making progress without both partners being present, however, so long as the above principle holds. One example that we will permit that would not be allowed under the COS 126 policy is working on the assignment in office hours that only one partner can attend (though we do encourage you to find a mutually-agreeable office hour to attend!).

Exam Conduct

Conduct during exams is covered by the University Honor Code. If we suspect a student of inappropriate conduct during either the midterm or final exam, then we will refer the case to the Honor Committee. If the Honor Committee (or other appropriate body) finds the student guilty of inappropriate conduct, then the standard penalty is automatic failure of the COS 217 course. The Honor Committee may impose additional penalties.

Assignment Late Submission

You should submit your work on an assignment before its due time. If you submit your work late, we will give you credit for it on this scale:

If an assignment consists of multiple files, then we will consider the date/time of submission of your work as a whole to be the same as the date/time of submission of the last file that you submit.

If you will be submitting after the deadline, you must submit a file named notdone for the assignment to indicate that your work is incomplete. You can create such a file and submit it for assignment X with these commands:

touch notdone
submit X notdone

If the deadline has passed and this file is not submitted, we may grade the submitted work as-is.

When you have finalized your work, you must retract the notdone file. We may not grade your submission until you have done this. You can do so with the command: unsubmit X notdone

You have four late days. You may use one or more of your late days on any assignment. Using one late day on an assignment extends the due date/time of that assignment by 24 hours, using two late days on an assignment extends the due date/time of that assignment by 48 hours, etc. If you wish to use one or more late days on an assignment, you must follow the notdone procedure above, and then in your finalized readme file you must declare how many late days you are using.

Some of the assignments involve partnering with another student. You may use X late days on a partnered assignment if and only if your partner also uses X late days on that assignment. The implication is that you may not use X late days on a partnered assignment if your partner has fewer than X unused late days. (A partner with more late days available would retain the excess for future assignments, if any.)

The final assignment is due at 5:00PM on Dean's Date, as is customary at Princeton University. You may submit the final assignment until 11:59PM on Dean's Date; in that case the appropriate lateness penalty will be applied. You may use a late day on the final assignment, but doing so extends the assignment due date/time only from 5:00PM on Dean's Date to 11:59PM on Dean's Date. You may not submit your work on the final assignment, or any assignment, after 11:59PM on Dean's Date without permission from the appropriate Dean and the COS 217 instructor-of-record.

For any assignment, we will grant extensions only in the case of illness or extraordinary circumstances. Typically these will require documentation and/or confirmation from your Dean or Director of Studies. In these cases, you should discuss the matter with your preceptor as soon as possible. Please plan your work on the assignments so that travel, religious holidays, etc. do not cause you to submit it late. Being overscheduled with a heavy workload is not an extraordinary circumstance.


Your final grade will be weighted as follows:

Component Approximate Weight
Assignments 66%
Midterm Exam 10%
Final Exam 20%
Participation 4%

To determine your participation grade we will consider the extent to which your involvement in the course positively affected the course as a whole. Did you attend and participate actively in class meetings? Did you participate effectively on Ed by asking helpful questions or providing helpful answers? If you can answer "yes" to those questions, then you have made the course a better experience for other students, for the instructors, and for yourself.

Conversely, we also will consider the extent to which your involvement in the course negatively affected the course as a whole. Did you miss class meetings frequently? Did you attend the wrong precept (without prior approval) frequently? Were you often distracted during meetings, or were you a source of distraction for others? Did you frequently send messages to Ed that are inappropriate, asking questions that were answered previously on Ed, or asking questions that are answered in the required readings? If you must answer "yes" to any of those questions, then you have negatively affected the course for all concerned.


The only person who can grant deviations from the above-stated policies is the COS 217 course's instructor-of-record, and such waivers will only be granted via e-mail or written communication. No other waiver from other sources can modify these policies. It is the student's responsibility to adhere to the policies, and to ignore any implied or explicit waiver from any unauthorized source. For example, if the student asks a preceptor, Lab TA, Dean, or friend if something is permissible, any response that deviates from course policy cannot be used to justify any action that is contrary to course policy.