This is not the current version of the class.

CS 61: Systems Programming and Machine Organization (2020)

Harvard School of Engineering and Applied Sciences
Eddie Kohler and Minlan Yu

Lectures: Flexible times, 3–4 times per week
Location: The Interwebs

Course Description  |  Schedule  |  Course staff, lecture viewing, and office hours  |  Infrastructure  |  Git  |  Coding style  |  C and C++ patterns
Piazza  |  Grading server



Minlan Yu and Eddie Kohler are co-teaching 61 in fall 2020. Most assignments will be similar to prior years, but the teaching methodology will change a lot.

Rather than conventional scheduled lectures, we’ve selected a Flex course model:

In shopping week, we will offer two sample lectures and visit times, on Wednesday 8/19 at 9:30am and Friday 8/21 at 4pm Eastern time. These will be recorded.


CS 61 is an introduction to the fundamentals of computer systems programming. Topics include C, C++, and assembly language programming, performance analysis and improvement strategies, memory management, caching, concurrency, threads, and synchronization.

CS 61 will help you develop the skills to write programs for the real world, where performance and robustness really matter. It will also prepare you for more advanced CS courses, including operating systems, compilers and programming languages, architecture, and graphics. We want it to be fun and challenging.

Full course description with policies


CS 50, CS 51, or the instructor’s permission.

Note: This course requires programming in C++. Ideally you should already have experience programming in C or C++. If you have not previously programmed in C or C++ but know another procedural language, such as Java, you will likely be able to quickly learn what you need. Talk to one of the instructors if you are unsure whether you are sufficiently prepared for CS 61, or do the ungraded warmup assignment to check your preparation.


Computer Systems: A Programmer’s Perspective, Third Edition by Randal E. Bryant and David R. O’Hallaron. More information

College concentration requirements

CS concentrators must take two of CS 50, CS 51, and CS 61. CS 61 may be used as one of the four half-courses in CS to satisfy the requirements for the secondary concentration in computer science. CS 61 may also be used as a technical elective for the primary concentration (if you don't use it to fulfill other requirements).

Extension school

CS 61 is offered through the Extension School as CSCI E-61. See information for Extension students.

Prior offerings