CS50 Introduction to Computer Science
Harvard University
Source: Edx On-line course
Paper - Abstract

Paper SummaryNotes Citing this PaperText Colour-Conventions

  1. Introduction & Schedule
    • Demanding, but definitely doable. Social, but educational. A focused topic, but broadly applicable skills. CS50 is the quintessential Harvard (and Yale!) course.
    • This is CS50 (aka CS50x through edX), Harvard University's introduction to the intellectual enterprises of computer science and the art of programming.
    • Did you start CS50 before 2017 but not finish? Not to worry. Scores from past years will (soon) be imported into CS50x 2017. However, moving forward, you must submit CS50x 2017's problem sets.
    • What’s new in CS50x 2017 vis-à-vis CS50x 2016!
      1. Machine Learning: CS50x now covers a bit of machine learning (ML), thanks to Patrick Rebeschini at Yale.
      2. Python1: Most of CS50x is still taught in C, but as of 2017, PHP has been replaced with Python.
      3. SQLite2: CS50x now introduces SQL using SQLite instead of MySQL.
      4. Videos: Instead of two lectures per week (as in 2016), CS50x now has one lecture per week, albeit longer. But you can now watch those lectures (on laptops and desktops) in CS50’s new-and-improved video player, thanks to CS50’s own Luke Jackson.
      5. Virtual Reality: Each of CS50x’s lectures can now be viewed in 360º stereoscopic virtual reality (VR) using Google Cardboard, HTC Vive, Oculus Rift, Samsung Gear, or YouTube’s mobile app.
      6. Sections, Shorts: In 2016, Doug’s "sections" were a bit of a misnomer, since they were really just short, non-interactive videos, just like the course’s actual "shorts." And they were also a bit redundant with the course’s actual shorts, which have been showing their age, not to mention time-consuming to watch! For 2017, then, each week of CS50x has one lecture and zero or more shorts (and no "sections").
      7. Seminars: Thanks to CS50’s TFs and CAs, new to CS50x are seminars on:
        • Automated Analysis of Music and Audio
        • Chrome Extensions
        • Data Analytics with Meteor.js + ReactJS
        • Data Science with Python Pandas
        • Data Visualization with D3
        • Drawing Real Web Apps with Pagedraw
        • An Introduction to Git and GitHub
        • JavaScript with Exponent and React Native
        • Making the Most of Bootstrap
        • P vs. NP
        • Smart Cities Data
      8. Problem Sets: Problem Sets 0 through 5 are largely unchanged, though "Hacker Editions" have been replaced with "more-comfortable" problems. Meanwhile Problem Set 6 (in Python) is entirely new this year, and Problem Set 7 and Problem Set 8 have also been ported to Python.
      9. Software: CS50 IDE now comes with debug50 (a new-and-improved graphical debugger for C) and help50 (a command-line tool that can help you understand (many!) C error messages), There are also some changes to the CS50 C Library.
    • You are welcome to take CS50 at your own pace, starting whenever you'd like. So no worries if this is your first time here! The course's materials will be updated on 1 January 2018, but any scores you receive in 2017 will be carried over into 2018.
    • There are CS50 accounts on Facebook, Twitter, Instagram, and Snapchat for those so inclined.
    • Visit the Course tab at top-left to dive into Week 0. In particular,
      1. Submit the Important Pre-Course Survey,
      2. Watch Week 0’s lecture,
      3. Optionally watch Week 0’s short
      4. Submit Problem Set 0, and then
      5. Rinse, wash, and repeat with Week 1 onward
    • Within 2 weeks of submitting any problem set, check your score via Progress up top. Problem Sets 1 through 6 are graded on multiple-point scales; Problem Sets 0, 7, and 8 are graded on 1-point scales.
    • Be sure to submit the Final Project anytime before 31 December 2017.
    • If you have any questions, start a discussion with classmates!
    • Schedule3: You are welcome to take CS50x at your own pace, so long as you submit nine problem sets and submit a final project no later than 31 December 2017. To help keep you on track, allow us to propose a schedule of deadlines for you, if only for a bit of psychological pressure, but you do not have to submit by these dates. In fact, these proposed deadlines will be extended automatically as time passes. The only hard deadline is 31 December 2017, by which you must submit nine problem sets and a final project.
    • Problem Set Deadlines - “try to submit by” …
      1. 27 December 2016
      2. 2 February 2017
      3. 11 March 2017
      4. 17 April 2017
      5. 24 May 2017
      6. 30 June 2017
      7. 6 August 2017
      8. 12 September 2017
      9. 19 October 2017
      10. Final Project: submit by 31 December 2017
  2. Description: Introduction to the intellectual enterprises of computer science and the art of programming. This course teaches students 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. Designed for majors and non-majors alike, with or without prior programming experience.
  3. Expectations: You are expected to submit nine problem sets and a final project.
  4. Website: This course lives at Web Link. Visit the course’s website to watch videos, to get help, to download handouts and software, and to follow links to other resources.
  5. Books4: No books are required for this course. However, you may want to supplement your preparation for or review of some lectures with self-assigned readings relevant to those lectures' content from either of the books below. The first is intended for those inexperienced in (or less comfortable with the idea of) programming. The second is intended for those experienced in (or more comfortable with the idea of) programming.
    • For Those Less Comfortable: C Programming Absolute Beginner’s Guide, Third Edition, Greg Perry, Dean Miller, Pearson Education, 2014, ISBN 0-789-75198-4
    • For Those More Comfortable: Programming in C, Fourth Edition, Stephen G. Kochan, Pearson Education, 2015, ISBN 0-321-77641-0
    • Recommended for those interested in understanding how their own computers work for personal edification. How Computers Work, Ninth Edition, Ron White, Que Publishing, 20085, ISBN 0-7897-3613-6
    • Recommended for aspiring hackers, those interested in programming techniques and low-level optimization of code for applications beyond the scope of this course. "Warren (Henry S.) - Hacker's Delight".
  6. Lectures: A schedule of lectures, subject to change, appears below.
    1. Binary. ASCII. Algorithms. Pseudocode. Source code. Compiler. Object code. Scratch. Statements. Boolean expressions. Conditions. Loops. Variables. Functions. Arrays. Threads. Events.
    2. Linux. C. Compiling. Libraries. Types. Standard output.
    3. Casting. Imprecision. Switches. Scope. Strings. Arrays. Cryptography.
    4. Command-line arguments. Searching. Sorting. Bubble sort. Selection sort. Insertion sort. O. Ω .Θ. Recursion. Merge Sort.
    5. Stack. Debugging. File I/O. Hexadecimal. Strings. Pointers. Dynamic memory allocation.
    6. Heap. Buffer overflow. Linked lists. Hash tables. Tries. Trees. Stacks. Queues.
    7. TCP/IP. HTTP.
    8. HTML. CSS. PHP.
    9. MVC. SQL.
    10. JavaScript. Ajax.
    11. Security. Artificial intelligence.
    12. Artificial intelligence, continued.
    13. Exciting conclusion.
  7. Sections: Lectures are supplemented by weekly, 90-minute sections led by the teaching fellows. Sections provide you with opportunities to explore the course’s material in a more intimate environment.
  8. Postmortems: Available after problem sets' deadlines are "postmortems," videos via which the course’s staff explore actual solutions to problem sets. You are expected to watch postmortems for insights into how else you could have (or should have!) implemented your own solutions.
  9. Problem Sets:
    • Nine problem sets are assigned during the semester. Each is due by 31 December 2017.
    • In order to accommodate students with different backgrounds, some problem sets are released in two editions: a standard edition intended for most students and a "Hacker Edition" intended for some students. Both editions essentially cover the same material. But the Hacker Edition typically presents that material from a more technical angle and poses more sophisticated questions.
    • To receive a Verified Certificate from HarvardX, you must submit the standard editions of problem sets. You are welcome to do the Hacker Editions for your own edification, but it is not possible to submit Hacker Editions for credit (or extra credit).
    • A schedule of problem sets appears below.
      1. Scratch
      2. C
      3. Crypto
      4. Game of Fifteen
      5. Forensics
      6. Mispellings
      7. Sentimental
      8. C$50 Finance
      9. Mashup
  10. 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. You may implement your project in any language(s), and you are welcome to utilize infrastructure other than the CS50 Appliance. All that we ask is that you build something of interest to you, that you solve an actual problem, 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.
    • See Web Link for details.
  11. 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. Collaboration on problem sets is not permitted except to the extent that you may ask classmates and others for help so long as that help does not reduce to another doing your work for you. Generally speaking, when asking for help, you may show your code to others, but you may not view theirs, so long as you and they respect this policy’s other constraints. Collaboration on the course’s final project is permitted to the extent prescribed by its specification.
    • 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.
      1. Reasonable:
        • Communicating with classmates about problem sets' problems in English (or some other spoken language).
        • Discussing the course’s material with others in order to understand it better.
        • Helping a classmate identify a bug in his or her code at Office Hours, elsewhere, or even online, as by viewing, compiling, or running his or her code, even on your own computer.
        • Incorporating snippets of code that you find online or elsewhere into your own code, provided that those snippets are not themselves solutions to assigned problems and that you cite the snippets' origins.
        • Reviewing past semesters' quizzes and solutions thereto.
        • Sending or showing code that you’ve written to someone, possibly a classmate, so that he or she might help you identify and fix a bug.
        • Sharing snippets of your own code online so that others might help you identify and fix a bug.
        • Turning to the web or elsewhere for instruction beyond the course’s own, for references, and for solutions to technical difficulties, but not for outright solutions to problem set’s problems or your own final project.
        • Whiteboarding solutions to problem sets with others using diagrams or pseudocode but not actual code.
        • Working with (and even paying) a tutor to help you with the course, provided the tutor does not do your work for you.
      2. Not Reasonable
        • Accessing a solution in CS50 Vault to some problem prior to (re-)submitting your own.
        • Asking a classmate to see his or her solution to a problem set’s problem before (re-)submitting your own.
        • Decompiling, deobfuscating, or disassembling the staff’s solutions to problem sets.
        • Failing to cite (as with comments) the origins of code or techniques that you discover outside of the course’s own lessons and integrate into your own work, even while respecting this policy’s other constraints.
        • Giving or showing to a classmate a solution to a problem set’s problem when it is he or she, and not you, who is struggling to solve it.
        • Looking at another individual’s work during a quiz.
        • Paying or offering to pay an individual for work that you may submit as (part of) your own.
        • Providing or making available solutions to problem sets to individuals who might take this course in the future.
        • Searching for, soliciting, or viewing a quiz’s questions or answers prior to taking the quiz.
        • Searching for or soliciting outright solutions to problem sets online or elsewhere.
        • Splitting a problem set’s workload with another individual and combining your work.
        • Submitting (after possibly modifying) the work of another individual beyond allowed snippets.
        • Submitting the same or similar work to this course that you have submitted or will submit to another.
        • Submitting work to this course that you intend to use outside of the course (e.g., for a job) without prior approval from the course’s heads.
        • Using resources during a quiz beyond those explicitly allowed in the quiz’s instructions.
        • Viewing another’s solution to a problem set’s problem and basing your own solution on it.
  12. Copyright © David J. Malan
  13. Instructions:
    • Per the syllabus, CS50x comprises 12 weeks of material, Week 0 through Week 12.
    • Within each week, you’ll typically find:
      • One or two lectures. Taught by David in Sanders Theatre at Harvard University, lectures present the week’s concepts through examples and demonstrations (sometimes followed by cake).
      • A few walkthroughs. Taught by David in CS50’s studio, walkthroughs walk you through the week’s source code (i.e., programming examples) in more detail than in lecture and at a slower pace.
      • A section (for all comfort levels). Taught by Doug Lloyd '09 in CS50’s studio, sections provide you with opportunities to review the course’s material at a slower pace.
      • A few shorts. Also filmed in CS50’s studio, shorts are bite-sized videos that focus in detail on a particular topic. Presented by CS50’s on-campus staff.
      • A problem set. Problem sets are programming assignments that challenge you to apply concepts to problems inspired by real-world domains. Embedded in each problem set are additional walkthroughs, taught by Zamyla Chan '14 or David in CS50’s studio, via which you receive direction on where to begin and how to approach the week’s challenges.
  14. How to Take CS50x
    • To take CS50x, then, simply start working your way through Week 0 through Week 12. For each week:
      1. Watch the week’s lecture(s).
      2. Optionally watch the week’s walkthroughs.
      3. Optionally watch the week’s section.
      4. Optionally watch the week’s shorts (unless required by the week’s problem set).
      5. If the week includes a problem set, read its "specification" and then dive into the problem set itself by following the specification’s instructions. Note that the "standard editions" of some problem sets are accompanied by "Hacker Editions," which are entirely optional. To receive a Verified Certificate from edX, you must submit the standard editions of problem sets.
      6. Submit the problem set per its directions.
      7. In addition to problem sets, the course also has a final project. See its specification for details.
    • Of course, if you do not wish to receive a Verified Certificate from HarvardX, you’re welcome to take CS50x however you’d like! All of CS50’s content will remain available at CS50.tv as OpenCourseWare after 31 December 2016, so not to worry if you don’t get through it in time!


See Web Link.

In-Page Footnotes

Footnote 1:
  • I suppose this is both good and bad news – Python is more trendy that PHP, but the latter would be good to know as well.
Footnote 2:
  • That’s a shame – MySQL sounds essential to have in your tool-kit.
Footnote 3:
  • As is noted, this is a non-binding self-study schedule that spreads the work out so you just complete by the final deadline.
  • The Harvard schedule seems to be 13-week for lectures and presumably some extra time for the final project.
Footnote 4: Footnote 5:

Text Colour Conventions (see disclaimer)

  1. Blue: Text by me; © Theo Todman, 2017
  2. Mauve: Text by correspondent(s) or other author(s); © the author(s)

© Theo Todman, June 2007 - August 2017. Please address any comments on this page to theo@theotodman.com. File output:
Website Maintenance Dashboard
Return to Top of this Page Return to Theo Todman's Philosophy Page Return to Theo Todman's Home Page