The CS50 team include Professor Zhou, one graduate teaching assistant, seven undergraduate teaching assistants, and five learning fellows.

Professor: Xia Zhou

Graduate assistant: Providing additional assistance and grading

Undergraduate assistants: Serving as Section leaders and graders

Learning fellows: Supporting in-class active learning, and guiding project teams

We are primarily using Slack for questions and answers. If you need a private communication with the teaching team, you can contact us by email, visit us (virtually) during office hours, or make an appointment.

Student groups: check this Google sheet

Prerequisites: Successful completion of Computer Science 10.

Student responsibilities

  • Watch the lecture video released on Canvas before each lecture.
  • Join the class with questions and engage in team activities. (If your time zone makes it difficult to be present all the time, coordinate with your team mates to seek opportunities outside lecture time for group activities.)
  • Attend weekly section meetings or come to office hours for questions related to labs or course materials. (If your time zone makes it difficult to attend these helper hours, feel free to reach out to the TAs or the professor to make separate appointments for help.)
  • Do the weekly reading - it’s short.
  • Pay attention to Canvas for announcements.
  • Code and submit Labs 1-6; see the policies below on late submissions.
  • Engage fully with your project team, striving to produce well-designed, well-documented, well-tested, well-styled code.

Lectures, office hours, sections

MWF 11:45-12:50
X-hour: Tu 12:30-1:20
Zoom link

Office hours: Note: these links are different from the Zoom link for class meetings.

  • Xia: 4-5pm ET Monday & Friday at Zoom
  • Yijing: 11am-12pm ET Saturday at Zoom

We are adopting a flipped classroom format, where short lecture videos are released before each class for you to watch and lecture time is used for Q/A and team activities. For maximize your learning efficiency, please make sure to watch the video beforehand and come to class with questions.

Also, if your network bandwidth allows, we do hope you keep your video on, as this has been shown to provide better interactivity and promote learning efficiency.

Learning Fellows

This course involves active learning, and you are expected to be engaged during each class meeting time. Learning Fellows are here to facilitate this through peer instruction, which is critical to your learning in this course because your reasoning skills will develop most effectively when you are actively engaged with this material and research has shown that cooperative learning is one of the best ways to achieve this engagement.

Given the online format, we will use Zoom breakout rooms for group activities. The Professor and Learning Fellows will circulate across breakout rooms, promoting useful dialog and providing feedback. Your questions and feedback will help shape the course based on your questions and ideas. If you have questions and would like to draw host attention, you can use the “Ask for help” button.

If you have questions about the Learning Fellow Program, please reach out to me, or vist


Please see the schedule for the complete list of topics that we will cover. The schedule is subject to change and I will try to update this pdf when changes occur.

Some assignment deadlines, further out in the term, are still tentative.

The x-hour periods in the first half of the term will be used for advancing course materials, while the x-hour periods in the second half the term will be used mainly as a help time on labs.


Section meetings give you an opportunity to work closely with an undergraduate teaching assistant on a hands-on activity that reinforces what we do in class. You should attend at least one section every week.

If you have a conflict with your usual section meeting time, in a particular week, feel free to attend a different section that week - just blitz your regular section leader know, and check in with the leader of the section you attend.

Leader Day Time Zoom Link
Kathy Monday 7-8pm
Abby Tuesday 7-8pm
Annie Wednesday 4:30-5:30pm
Clay Thursday 5-6pm
Hunter Thursday 7-8pm
Katherine Friday 1-2pm
Issac Sunday 3-4pm

Course Announcements

The instructor will make announcements via Canvas and Slack.

We will use Slack for class discussion and Q/A, Canvas for announcement and grades. All lab assignments will be announced in the Assignment section of our Canvas site. You will receive all your feedback and grades via that site. Access to the Canvas site is limited to those enrolled in the course.


Reading assignments

You are encouraged to read all the assigned readings listed before class each week, but you are expected to have read these readings before the next week.


Students will work individually on a series of six coding assignments (“labs”), which get progressively harder through the term. All labs are submitted through GitHub Classroom (GitHub). We will test all your solutions on Thayer Linux servers, so you should develop and test (or at least test) your code there.


Students will work on projects in small groups assigned by the instructor; details will be announced later in the term. After the project is submitted, each member of a group will submit a confidential assessment of themselves and the others in their group.

Access to Linux systems

You will do all your programming on Linux servers at Dartmouth’s Thayer School of Engineering. You will have to connect to the Dartmouth Campus network to access Thayer’s Linux servers. If you are off campus, please use Dartmouth’s VPN.

The primary CS50 server is called; you may also use equivalent servers called, where X is 1 through 8. (You can check their status here.) Your laptop must first be on the campus network, or on Dartmouth VPN, to access these servers.

In CS50 we support development only on Thayer’s Linux systems. Not MacOS, not Windows, not even other Linux systems. Linux systems differ in subtle ways; MacOS is a form of Unix different from Linux, and Windows is even more different. Our graders will use plank for all testing.

If you find yourself stuck or confused about Linux or any of the tools we use, here are some places to look:

  • For help with Dartmouth-supported services check the Knowledge Portal, which has helpful pages about Canvas, Slack, VPN, Zoom, and more. If you’re really stuck, email or call their helpdesk for personalized help. (The phone number is at the bottom of every page on the Knowledge Portal.)

  • For help using the Thayer Linux computer systems, look here first. If you don’t find an answer there, search the #help-systems channel on our workspace to see if others may have had and resolved your issue or, if not, post a question there. If neither of those help, then send email to Thayer Computing Services for support. (Keep in mind they are only active during normal business hours.)

  • For help about CS50-specific issues, use Slack.


There are no exams in this class – instead, a series of programming exercises and a final project.

Component Percentage
Shell Lab 1 8%
C intro Labs 2-3 20%
TSE Labs 4-6 36%
Final project grade 26%
Class engagement 10%

The final project is a team grade – every team member gets the same grade – but there is an opportunity for peer evaluation to address variance in members’ contribution.

Class engagement will be assessed on attendance and participation in activities in class. Engagement requires both preparation and participation - you should read ahead, think ahead, and actively participate.

Class Attendance counts toward “engagement”. You are expected to attend and engage actively in classroom activities. If your time zone makes it challenging for you to be present during the whole lecture time, being present during part of the lecture time would still be very beneficial because you can use that time to work with your team mates for group activities. Do reach out to your team mates about your constraints so that your team can explore time outside the lecture time for group activities.

Lab grades depend on whether your submission meets the requirements for that lab, and being submitted on time. See the lateness policies below.

Homework grading/regrading

Your work is normally graded each week by the teaching assistants, according to a grading rubric that I discuss with them. If you have any grading questions on a homework or quiz, please follow the procedure below.

If the grader made an obvious mistake (e.g., totaling error), you can see me or the TA and we’ll make the correction right away.

If you feel the grader did not grade your answer accurately, then you should send email to both the grader and me to explain which program(s) need regrading and why. We will arrange for your answer to be reviewed again. After you hear the outcome on your regrade request, if you still feel the matter is not resolved satisfactorily, then you should see me.

You must submit your regrade request within four days from when the homework/exam was returned, or 5PM August 27, 2021, whichever is earlier.

Please note that any regrade request that comes after the deadline stated above will not be considered, regardless of its merit.

Programs that crash

Your lab solutions are graded on correctness, style, design, and documentation. Each lab requires you to document your own tests and test results; the graders will also compile and run your program with their own test cases. If your program crashes when the graders run a particular test, your program will be marked as incorrect for that test. If your program does not compile, you will lose all correctness points. The best way to avoid that situation is to ensure that your program doesn’t crash in the first place. Learning how to debug and test your programs is a key part of this course.

Late assignments

This is a challenging course, so self-discipline and planning will be key to your success. In short, Start Early!

Late assignments will be penalized:

  • 10% of the whole lab’s points if submitted within 24 hours after the deadline,
  • 20% of the whole lab’s points if submitted within 48 hours after the deadline,
  • 30% of the whole lab’s points if submitted within 72 hours after the deadline.

As an example, if it’s due at 11:50PM on 25-July and you submit it at 1:00AM on 26-July, and the total points of the lab is 100 points, 10 points will be deducted from your final score.

No assignments will be accepted 72 hours after the original deadline. At that point, you will receive zero points for the lab.

Honor code

Dartmouth’s Honor Code and policies apply to your conduct in this course. Please read about Dartmouth’s Academic Honor Principle.

First, you may discuss and help each other (help in debugging, sharing knowledge, giving moral support, getting coffee, etc.). This support is the type of team spirit and joint problem-solving skills that are the essence of the course and necessary to do a great project. However, you cannot work jointly on coding up (i.e., writing) your individual programming assignments. You can talk, discuss solutions to solve a problem but you cannot jointly work on the code development and writing. Submitted code for the labs has to be yours and yours alone.

The project phase is different. You can work jointly with your project team on writing code and documentation. But you cannot take code from anywhere (e.g., the web or any other source). It has to be the joint product of the team. No sharing of code between teams. As above, teams can discuss code, show each other snippets on the white board, but not share source code.

In either case, you should not read and directly incorporate solutions for assignments found on the Web (including websites for previous terms, inside or outside of Dartmouth).


We will also be learning how to share files using the git source code control system. We will use git with GitHub, which is an open repository of projects (including source code) from programmers around the world. Some past students of CS50 uploaded their assignment or project solutions to GitHub for reference by potential employers. While this is may be a good idea for their job search, it is extremely disruptive, distracting, and misleading for you and future students.

Keep in mind:

  • Anyone can upload code to GitHub. That doesn’t mean it’s good code, working code, or even code that will compile and run! If you take freely available code and study it sufficiently to be sure it works properly and isn’t evil, you might as well write it yourself.
  • If you need to upload your work for reference by potential employers, make the repo private. GitHub offers free unlimited private repositories to students.
  • Any student found to have uploaded any CS50 assignment solutions, including TSE and the final project, to a publicly available GitHub repository, or to a private GitHub repository while sharing its access credentials with other Dartmouth students, will be reported.
  • Anyone caught using the work of prior CS50 students, whether from GitHub or other sources, will be reported.
  • The graders have a list of existing public repos hosting CS50 related labs, and will compare your submission to them to detect plagiarism.

The following is repetitive, but it is necessary to be explicit here (this is Prof. Campbell’s version):

You would be amazed at how easy it is to tell when people work together on problem sets, particularly coding exercises. Think about the simple shell commands we run against your source code from labs and projects to compare your lab assignments and projects against every other assignment and project ever submitted since this revision of course started in 2008 - it takes less that a millisecond to run these checks - no effort on our behalf. Similarly, we know how to use google too. You should not under any circumstance look at or use code from students that have previously taken this course. The message is simple - please don’t make life unpleasant for all of us by breaking these rules. The penalties for cheating at Dartmouth are severe, starting with suspension and including expulsion. If you are unsure about anything, please ask.

We can assure you that violations of the Honor Code have been, and will continue to be, treated seriously.

Indeed, I agree with Professor Cormen, who wrote:

I reserve the right to assign you a failing grade on an entire homework assignment or on an entire exam if I believe that you have violated the Academic Honor Principle, apart from any finding by the COS. I will give you every opportunity to convince me that you did not violate the Academic Honor Principle, but I take the Academic Honor Principle very seriously. You have read Sources and Citation at Dartmouth College. I was co-chair of the committee that wrote this document. In fact, I wrote the first draft. So I know exactly what it says. Cheaters—whether or not they are caught—bring dishonor upon themselves and upon everyone else at Dartmouth. To do that, for just a few lousy points in a course, is [insert your favorite strong adjective meaning “stupid” here]. You cannot fool me into thinking that you did not cheat if, in fact you did. So don’t cheat.

Please let me know if you have any questions—better to be safe than sorry!

Credit your sources

Any ideas you get from other teams or any other source should be carefully cited both in the code and in the documentation.

  • In your assignments, list all your collaborators (e.g., “I discussed this homework with Alice, Bob, …”) and credit any sources (including code) used.
  • You must also credit specific sources that are provided by the instructor. For example, you must credit code that we give you if it helps you with your work (either by direct use of the code, or by simply enhancing your understanding by reading the code).
  • References for any non-trivial algorithms you employ should be included in the code and documentation to ensure others will know where to learn more about it.

Copying code from StackOverflow or other online sources is strictly forbidden. The code you submit must be your own.

For more general information, see Dartmouth’s guidelines for proper citation of sources, particularly the section on Computer programming assignments.

Special accommodations

Students with disabilities who may need disability-related academic adjustments and services for this course are encouraged to see me privately as early in the term as possible. Students requiring disability-related academic adjustments and services must consult the Student Accessibility Services office (205 Collis Student Center, 646-9900, Once SAS has authorized services, students must show the originally signed SAS Services and Consent Form and/or a letter on SAS letterhead to their professor. As a first step, if students have questions about whether they qualify to receive academic adjustments and services, they should contact the SAS office. All inquiries and discussions will remain confidential.

Religious observations

I realize that some students may wish to take part in religious observances that fall during this academic term. Should you have a religious observance that conflicts with your participation in the course, please come speak with me before the end of the second week of the term to discuss appropriate accommodations.

Inclement weather

On rare occasions, Dartmouth may cancel classes or even close the campus. If this occurs, general notice will be given in three ways:

  • Local broadcast media;
  • Campus-wide BlitzMail messages; and
  • A recorded message at a College toll-free Inclement Weather Phone Line: 1-888-566-SNOW (1-888-566-7669).