This is not the current version of the class.

CS 61: Systems Programming and Machine Organization (2021)

Harvard School of Engineering and Applied Sciences
Eddie Kohler

Lectures: Tuesday and Thursday, 11:15am–12:30pm
Location: SEC 1.321 Lecture Hall, Allston

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Git  |  Coding style  |  C and C++ patterns
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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.

The 2021 offering of the course will include more material on software engineering, such as testing code and reasoning about code.

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 and readings by topic

College concentration requirements

CS 61 satisfies the Programming 2 and Systems requirements for the computer science concentration, and may be used as one of the four CS courses to satisfy the requirements for a secondary field in computer science.

Extension school

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

Prior offerings