Introduction to the intellectual enterprises of computer science and to the art of programming. Students learn how to think algorithmically and solve problems efficiently. Topics include abstraction, algorithms, data structures, encapsulation, resource management, security, software engineering, and web development. Languages include C, Python, SQL, and JavaScript, plus CSS and HTML. Problem sets inspired by real-world domains of biology, cryptography, finance, forensics, and gaming. See CS50’s website,, for additional information.

No previous programming experience required. Open to students of all levels and majors.

CS50 officially meets on Thursdays, from 4pm until 5:15pm in Sheffield-Sterling-Strathcona Hall (SSS) Room 114, but students are only expected to attend in person the course’s first lecture on Thursday 8/30, second lecture on Thursday 9/6, and final lecture on Thursday 11/15. If you have a time conflict with any of those lectures, you should watch the recordings instead. Required sections to be arranged.


You are expected to


You are encouraged to take CS50 Credit/D/Fail if you will feel less nervous without the pressure of a letter grade. Note however, that first years are generally discouraged from taking classes Credit/D/Fail in their first term, and it will only satisfy the QR requirement if you take it for a grade. Please also remember that your course grade will reflect how much you progress over the semester. We expect you to work hard and learn a lot, and your course grades will reflect that.

Whether taking the course Credit/D/Fail or for a letter grade, you must ordinarily submit all nine problem sets, take one quiz, and submit a final project unless granted an exception in writing by the course’s heads. Multiple missing problem sets, a missing quiz or final project, and violations of the academic honesty policy may each result in a reduced or failing grade.

Graduate and professional students are expected to produce a final project that is 50% greater in scope than what is expected of undergraduate students. Your course grade will be adapted to the prevailing standards of your school, but we encourage you to take the class Pass/Fail if your degree program permits it.

Auditors are welcome in CS50. Graduate students, employees, and their family members who formally register as auditors may also participate in all aspects of the class including section, office hours, and receiving graded feedback on your problem sets. We do not require or expect you to complete all the coursework like a regular student, and we will not worry if you choose not to. However, we will not be able to help you individually catch up or grade late submissions if you have not been fully participating in the class.

Final grades are determined using the following weights:

Problem Sets 60%
Quiz 20%
Final Project 10%
Engagement 10%

Problem sets and the final project are evaluated on correctness, design, and style, with scores ordinarily computed as 3 × correctness + 2 × design + 1 × style. Engagement takes into account attendance at sections, attendance at office hours, participation in the course’s online discussion forum, and/or other forms of engagement. Scores are normalized across teaching assistants and comfort levels at term’s end, so mid-semester comparisons among students of scores are not reliable indicators of standing.

Know that CS50 draws quite the spectrum of students, including “those less comfortable,” “those more comfortable,” and those somewhere in between. However, what ultimately matters in this course is not so much where you end up relative to your classmates but where you, in Week 10, end up relative to yourself in Week 0.

Each student’s final grade is individually determined by the instructors at term’s end. Remarkable effort and upward trending are considered, as is input from the teaching assistants. The course does not have pre-determined cutoffs for final grades. The course is not graded on a curve. Those less comfortable and somewhere in between are not at a disadvantage vis-à-vis those more comfortable.


No books are required or recommended for this course. However, you might find the below books of interest. Realize that free, if not superior, resources can be found on the course’s website.

C Programming Absolute Beginner’s Guide, Third Edition
Greg Perry, Dean Miller
Pearson Education, 2014
ISBN 0-789-75198-4

Hacker’s Delight, Second Edition
Henry S. Warren Jr.
Pearson Education, 2013
ISBN 0-321-84268-5

How Computers Work, Tenth Edition
Ron White
Que Publishing, 2014
ISBN 0-7897-4984-X

Programming in C, Fourth Edition
Stephen G. Kochan
Pearson Education, 2015
ISBN 0-321-77641-0


CS50 officially meets on Thursdays, from 4pm until 5:15pm in Sheffield-Sterling-Strathcona Hall (SSS) Room 114, but students are only expected to attend in person the course’s first lecture on Thursday 8/30, second lecture on Thursday 9/6, and final lecture on Thursday 11/15. If you’ve a conflict, though, you’re welcome to watch those lectures online.

Other lectures are live-streamed from Harvard on Fridays, though you’re welcome to watch on demand anytime thereafter. On Thursdays, CS50 holds “enrichment” in SSS 114 for students who would like additional context and depth on some of the topics covered in class. Attendance is optional, but encouraged if you do not have a conflict. Because these will not be “review” or “help” sessions, you will not be at any disadvantage if you are unable to attend.

A schedule of lectures, subject to change, appears below.

Week 0 Thu 8/30, 4pm – 5:15pm, live at Yale
Week 0, continued Thu 9/6, 4pm – 5:15pm, live at Yale
Week 1 Fri 9/14, 9am – 11:45am, filmed at Harvard
Week 2 Fri 9/21, 9:30am – 11:45am, filmed at Harvard
Week 3 Fri 9/28, 9:30am – 11:45am, filmed at Harvard
Week 4 Fri 10/5, 9:30am – 11:45am, filmed at Harvard
Week 5 Fri 10/12, 9:30am – 11:45am, filmed at Harvard
Week 6 Fri 10/19, 9:30am – 11:45am, filmed at Harvard
Week 7 Fri 10/26, 9:30am – 11:45am, filmed at Harvard
Week 8 Fri 11/2, 9:30am – 11:45am, filmed at Harvard
Week 9 Fri 11/9, 9:30am – 11:45am, filmed at Harvard
Week 10 Thu 11/15, 4pm – 5:15pm, live at Yale


Lectures are supplemented by weekly, 90-minute sections led by the teaching assistants. Different sections are offered for those less comfortable, those more comfortable, and those somewhere in between. You will sign up for a section in the Online Course Selection system starting Wed 9/5 at 9am. The times and distribution of comfort levels is based on the preferences many of you entered in the preference selection system.

Attendance at section is expected.

Office Hours

Office hours are opportunities for help with problem sets alongside the course’s teaching assistants and course assistants.

A schedule of office hours appears on the course’s website.

Each week, the instructors will offer additional time to discuss any and all of students’ questions, comments, and concerns about the course or computer science more generally. These dates and times will appear on the aforementioned schedule.


For students who avail themselves of the course’s other resources but still find themselves struggling, the course offers tutoring, to the extent possible, providing opportunities for students to work with the course’s staff one-on-one or in particularly small groups. To arrange, contact the course’s heads.

Problem Sets

Nine problem sets are assigned during the semester. Late work is not ordinarily accepted, except with a Dean’s excuse. (Graduate students should e-mail as early as possible to request an extension.)

A schedule of problem sets appears below.

Problem Set Language Released Due
Problem Set 0 Scratch Fri 9/7 Tue 9/11, 11:59pm
Problem Set 1 C Fri 9/14 Fri 9/21, 11:59pm
Problem Set 2 C Fri 9/21 Fri 9/28, 11:59pm
Problem Set 3 C Fri 9/28 Fri 10/5, 11:59pm
Problem Set 4 C Fri 10/5 Fri 10/12, 11:59pm
Problem Set 5 HTML, CSS Fri 10/12 Tue 10/16, 11:59pm
Problem Set 6 Python Fri 10/19 Fri 10/26, 11:59pm
Problem Set 7 Python, HTML, CSS Fri 10/26 Fri 11/2, 11:59pm
Problem Set 8 SQL, Python, HTML, CSS Fri 11/2 Fri 11/9, 11:59pm


Due by noon on Thu 11/15 is a take-home quiz that will cover Weeks 0 through 8 (and Problem Sets 0 through 8). The quiz is open-book: you may use any and all non-human resources during the quiz, but the only humans to whom you may turn for help or from whom you may receive help are the course’s heads.

Final Project

The climax of this course is its final project. The final project is your opportunity to take your newfound savvy with programming out for a spin and develop your very own piece of software. So long as your project draws upon this course’s lessons, the nature of your project is entirely up to you, albeit subject to the staff’s approval. You may implement your project in any language(s) as long as the staff approves. You are welcome to utilize any infrastructure, provided the staff ultimately has access to any hardware and software that your project requires. All that we ask is that you build something of interest to you, that you solve an actual problem, that you impact campus, or that you change the world. Strive to create something that outlives this course.

Inasmuch as software development is rarely a one-person effort, you are allowed an opportunity to collaborate with one or two classmates for this final project. Needless to say, it is expected that every student in any such group contribute equally to the design and implementation of that group’s project. Moreover, it is expected that the scope of a two- or three-person group’s project be, respectively, twice or thrice that of a typical one-person project. A one-person project, mind you, should entail more time and effort than is required by each of the course’s problem sets. Although no more than three students may design and implement a given project, you are welcome to solicit advice from others, so long as you respect the course’s policy on academic honesty.

Extensions on the final project are not ordinarily granted, except in cases of emergency. A Dean’s excuse is required. Lateness of submissions is determined down to the minute by submissions’ timestamps. Submitting more than seven minutes late is equivalent to not submitting at all.

Milestone Date
Pre-Proposal Tue 11/6, 11:59pm
Proposal Tue 11/13, 11:59pm
Status Report Tue 11/27, 11:59pm
CS50 Hackathon Thu 11/29, 7pm – Fri 11/30, 7am
Implementation Tue 12/4, 11:59pm
CS50 Fair Wed 12/5, 12pm – 2pm

CS50 Hackathon

From 7pm on Thu 11/29 until 7am on Fri 11/30 is the CS50 Hackathon, an epic all-nighter at Harvard during which you can dive into your final project’s implementation alongside classmates (from Yale and Harvard alike!) and staff. If you choose to partake, you’ll be asked to propose three milestones for yourself that evening: a “good” one that you intend to achieve no matter what; a “better” one that you think you can achieve; and a “best” one that you hope to achieve.

Dinner will be served around 9pm, second dinner will be served around 1am, and those still awake around 5am will be treated to breakfast at IHOP.

Transportation to and from Harvard will be provided.

CS50 Fair

From 12pm until 2pm on Wed 12/5 is the CS50 Fair, an epic display of final projects. Not only is the CS50 Fair a venue at which to see classmates’ projects and demo your own, it is an opportunity to mingle with students, faculty, and staff from across campus as well as recruiters from industry. Attendance is expected of all students.

Also in attendance are popcorn, candy, and a raffle with (fabulous) prizes. Family and friends are welcome to join.

Financial Aid

CS50 does not require that students purchase any books, hardware, or software. While not required, having one’s own laptop is helpful, particularly for office hours. Students without their own laptops are encouraged to reach out at term’s start to the course’s instructor and/or college dean to discuss possibilities.

Academic Honesty

This course’s philosophy on academic honesty is best stated as “be reasonable.” The course recognizes that interactions with classmates and others can facilitate mastery of the course’s material. However, there remains a line between enlisting the help of another and submitting the work of another. This policy characterizes both sides of that line.

The essence of all work that you submit to this course must be your own and you must explicitly cite anyone you collaborate with and any resources you use that are not part of the course material or directly linked from the pset instructions.

Regret clause. If you commit some act that is not reasonable but bring it to the attention of the course’s heads within 72 hours, the course may impose local sanctions that may include an unsatisfactory or failing grade for work submitted, but the course will not refer the matter for further disciplinary action unless another infraction occurs. You may invoke this clause only once for a true infraction, but if you self-report something that the course heads feel is not a significant violation, it will not count against you or count as your one invocation.

Brink clause. If push comes to shove, and you reach a breaking point this term, particularly late at night, and fear you’re about to commit some act that is not reasonable, you may, up to the last moment before you cross that point of no return, email the course’s heads to say that you see no other way out but invoke this clause. (And then go to sleep!) We will then meet with you and, together, get you back on track both work-wise and grade-wise.

In cases of suspected violations involving students at both Harvard and Yale, students will be referred to the appropriate committee at their university. Those committees may exchange information for the purpose of resolving the cases in accordance with their own procedures. They may also reach different conclusions and impose different sanctions from the same set of facts and evidence.

Below are rules of thumb that (inexhaustively) characterize acts that the course considers reasonable and not reasonable. If in doubt as to whether some act is reasonable, do not commit it until you solicit and receive approval in writing from the course’s heads. Acts considered not reasonable by the course are handled harshly. If the course refers some matter for disciplinary action and the outcome is punitive, the course reserves the right to impose local sanctions on top of that outcome that may include an unsatisfactory or failing grade for work submitted or for the course itself.


Not Reasonable

Acknowledgement and Authorization

Harvard plans to record audio, photos, and video of Computer Science 50 (CS50) lectures, sections, office hours, seminars, and other events and activities related to CS50 (the “Recordings”), with the aims of making the content of the course more widely available and contributing to public understanding of innovative learning (the “Projects”). The Recordings, or edited versions of them, may be made available to other Harvard students, to students at other educational institutions, and to the broader public via edX, the Internet, television, theatrical distribution, digital media, or other means. It is also possible that the Recordings may be used to make other derivative works in the future. Students may elect not to appear in photos and video used in the Projects and may still participate fully in CS50.

When you submit Problem Set 0, you will need to sign online an Acknowledgement and Authorization in the following form:

I understand that, if I do not wish any photos or video of me to be used as part of the Projects, I should so inform the course’s instructor by emailing within one week of enrolling in CS50. In that event, I understand that I should sit in the designated “no-film” zone of CS50 classrooms and should not walk in the field of view of the cameras. I understand that Harvard will take reasonable steps, with my cooperation, to avoid including identifiable images of me in the Projects’ photos and video shot in classrooms and other course locations after I opt out as just described. I understand that I am free to opt out of the Projects’ photos and video in this way, and that doing so will not affect my grade or my ability to participate in course activities.

Unless I opt out of the Projects’ photos and video as described above and take the steps that will be outlined by the instructor to avoid being filmed, I authorize Harvard and its designees to record and use photos and video of my participation in CS50 and activities related to CS50 (the “Recordings”). I understand and agree that the Recordings may include my image, name, and voice. I also understand and agree that, even if I opt out of the Projects’ photos and video, my spoken name and voice may be picked up by microphones outside the “no-film” zone and may be included in the Recordings.

I understand and agree that Harvard and its designees will have the irrevocable, worldwide right to make, edit, modify, copy, publish, transmit, distribute, sell, publicly display, publicly perform, and otherwise use and make available its respective Recordings and any other works that may be derived from those Recordings, in any manner or medium now known or later invented, and to authorize others to do so as well. I hereby transfer to Harvard any rights, including copyrights, I may have in the Recordings that Harvard makes. I will remain free to use and disseminate any ideas, remarks, or other material that I may contribute to course discussions.

I acknowledge and agree that I will not be entitled to any payment, now or in the future, in connection with the Recordings or any works derived from them. This Acknowledgment and Authorization is a binding agreement, and is signed as a document under seal governed by the laws of the Commonwealth of Massachusetts.

Unless you opt out as described in the Acknowledgment and Authorization, you are agreeing, by attending CS50, that your participation in CS50 and related activities may be recorded and used by Harvard in connection with the Projects without further obligation or liability to you, even if you do not sign any authorization.

If you have any questions about the above, contact