CS 31: Intro to Computer Systems — Fall 2026

This course is a broad introduction to computer science that focuses on how a computer works and how programs run on computers. We examine the hardware and software components required to go from a program expressed in a high-level programming language like C or Python to the computer actually running the program. This course takes a bottom-up approach to discovering how a computer works and introduces parallel and distributed computing with a specific focus on parallelism for multicore and other shared memory systems.

Topics include theoretical models of computation, data representation, machine organization, assembly and machine code, memory, I/O, the stack, the operating system, compilers and interpreters, processes and threads, and synchronization. In addition to parallel programming, we will discuss parallel computers and system-level support for parallel computing.

Prerequisite: Completion of CS21 or its equivalent.

This is a tentative schedule; it may change as we go. All section numbers refer to the Dive into Systems textbook unless otherwise indicated. You should read the assigned sections before class to prepare for reading quizzes.

Read tips for reading CS textbooks to help you determine what to focus on and how to get the most out of required readings.

Grades will be weighted as follows:

The CS31 Ninjas are student mentors who will assist students in class and lab, and who run evening study sessions each week. You are encouraged to participate in Ninja evening study sessions to get friendly assistance on lab assignments and help with preparing for exams.

To help with cases of minor illnesses, athletic conflicts, or other short-term time limitations, we will drop your 3 lowest reading quizzes and participation grades. You are still responsible for the material, and you should review any missed materials via the class recordings as soon as you can.

All students start the course with 2 "late assignment" days to be used on lab assignments at your discretion, with no questions asked. No more than 2 late days can be used on a single lab assignment.

To use your extra time, you must email Jocelyn Corey (jcorey1@swarthmore.edu) after you have completed the lab and pushed to your repository. You do not need to inform anyone ahead of time. When you use late day, you should still expect to work on the newly-released lab during the following lab section meeting. The professor will always prioritize answering questions related to the current lab assignment.

Your late days will be counted at the granularity of full days and will be tracked on a per-student (NOT per-partnership) basis. That is, if you turn in an assignment five minutes after the deadline, it counts as using one day. For partnered labs, using a late day counts towards the late days for each partner. In the rare cases in which only one partner has unused late days, that partner’s late days may be used, barring a consistent pattern of abuse.

If you feel that you need an extension on an assignment or that you are unable to attend class for two or more meetings due to a medical condition (e.g., extended illness, concussion, hospitalization) or other emergency, you must contact the dean’s office and your instructors. Faculty will coordinate with the deans to determine and provide the appropriate accommodations. For illnesses, students should consult the College’s medical excuse policy for the latest guidance on how you can coordinate with the student health and wellness center and your dean in order to provide us with the necessary information.

Late days cannot be used for any written or in-class homework assignments that are not associated with a lab assignment.

"If you believe you need accommodations for a disability or a chronic medical condition, please visit the Student Disability Services website for details about the accommodations process. Since accommodations require early planning and are not retroactive, contact Student Disability Services as soon as possible.

You are also welcome to contact the professor privately to discuss your academic needs. However, all disability-related accommodations must be arranged, in advance, through Student Disability Services."

To receive an accommodation for a course activity you must have an official Accommodations Letter and you need to meet with the course professor to work out the details of your accommodation at least two weeks prior to any activity requiring accommodations.

Academic honesty is required in all your work. Under no circumstances may you hand in work done with or by someone else under your own name. Discussing ideas and approaches to problems with others on a general level is encouraged, but you should never share your solutions with anyone else nor allow others to share solutions with you. You may not examine solutions belonging to someone else, nor may you let anyone else look at or make a copy of your solutions. This includes, but is not limited to, obtaining solutions from students who previously took the course or solutions that can be found online. You may not share information about your solution in such a manner that a student could reconstruct your solution in a meaningful way (such as by dictation, providing a detailed outline, or discussing specific aspects of the solution). You may not share your solutions even after the due date of the assignment.

In your solutions, you are permitted to include material which was distributed in class, material which is found in the course textbook, and material developed by or with an assigned partner. In these cases, you should always include detailed comments indicating on which parts of the assignment you received help and what your sources were.

Use of or consultation with generative AI (e.g., chatGPT or GitHub CoPilot) is considered to be unauthorized collaboration with another source and is a violation of our academic integrity policy.

When working on tests, exams, or similar assessments, you are not permitted to communicate with anyone about the exam during the entire examination period (even if you have already submitted your work). You are not permitted to use any resources to complete the exam other than those explicitly permitted by course policy. (For instance, you may not look at the course website during the exam unless explicitly permitted by the instructor when the exam is distributed.)

Failure to abide by these rules constitutes academic dishonesty and will lead to a hearing of the College Judiciary Committee. According to the Faculty Handbook:

This policy applies to all course work, including but not limited to code, written solutions (e.g. proofs, analyses, reports, etc.), exams, and so on. This is not meant to be an enumeration of all possible violations; students are responsible for seeking clarification if there is any doubt about the level of permissible communication.

The general ethos of this policy is that actions which shortcut the learning process are forbidden while actions which promote learning are encouraged. Studying lecture materials together, for example, provides an additional avenue for learning and is encouraged. Using a classmate’s solution, however, is prohibited because it avoids the learning process entirely. If you have any questions about what is or is not permissible, please contact your instructor.

Below are some resources and links that may be helpful to you.