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Harvard University · on edX

CS50's Introduction to Computer Science

Beginner 100 hours English University CertificateFREE
SkillsComputational thinkingCPythonSQLAlgorithmsMemory managementWeb basics

Is this course right for you?

Our take
One of the strongest introductions to computer science there is, and it is free. Just go in knowing it is demanding.

Good for: beginners and self-taught coders who want a rigorous, real foundation in computer science.

Skip if: you want a quick, gentle intro, or a narrow job-ready skill rather than fundamentals.

CS50 teaches how computing actually works rather than one language in a hurry. You move through C, then Python, SQL and some web, with problem sets that are genuinely hard and famously satisfying to finish. The rigour is what makes it valuable, and the same rigour is why people underestimate the time it takes.

It is a foundation, not a job-ready bootcamp. It will make you a stronger programmer and a sharper problem-solver, but you will still specialise afterwards. If you want a quick, gentle path this is not it. If you want to properly understand the fundamentals, few things are better.

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About this course

CS50's Introduction to Computer Science is Harvard's legendary first course in programming, taught by David Malan. It's free to audit on edX; a verified certificate is optional and costs around $199.

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Instructor

DJ
David J. Malan
edX instructor
4.5M learners8 courses4.9 instructor rating

David J. Malan is a Harvard professor whose energetic teaching turned CS50 into one of the most-taken courses in the world, on campus and online.

Frequently asked questions

At least 70% on each problem set and on the final project. If you fall short you can keep improving and resubmitting — there's no penalty for taking several attempts, and the point is that you genuinely complete the work.

No. CS50 assumes comfort with secondary-school maths at most; it's about problem-solving and logical thinking, not advanced mathematics. If arithmetic and a bit of algebra don't scare you, the maths won't be what makes it hard — the programming will, and that's the point.

You can, but it's worth resisting. CS50 starts with C so you understand what higher-level languages quietly do for you — memory, types, what a variable really is. The C weeks are the ones people find hardest and, afterwards, most often say were the most valuable. Push through them rather than around them.
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