How computers really think

Harvard's CS50x, the introduction to computer science, for people with or without prior programming experience.

Open the course on Harvard University See the walk-throughs

The course

Course: CS50's Introduction to Computer Science (CS50x)
Made by: Harvard University
Cost: Free
Language: C, Python, SQL, JavaScript

Even if you are not a student at Harvard, you are welcome to “take” this course for free via this OpenCourseWare
Harvard University, How to Take this Course

Certificates and credit are optional extras that Harvard and edX offer separately; the course itself is free.

CS50's Introduction to Computer Science (CS50x) is made and run by Harvard University, and it is free. We do not host or copy it: you learn on their site. The live walk-through, where your instructor works through it alongside you, is ours.

Weeks, as Harvard University names them

Week 0
Week 1
Week 2
Week 3
Week 4
Week 5
Week 6
Week 7
Artificial Intelligence
Week 8
Week 9
Week 10

A suggested pace

24 weeks at 6 to 10 hours a week. This is our suggestion, not the provider's; go slower whenever you need to.

Weeks 1 to 8Weeks 0 to 3
Weeks 9 to 16Weeks 4 to 7 and Artificial Intelligence
Weeks 17 to 24Weeks 8 to 10 and the final project

What you will build

The course's problem sets
A final project of your own

Instructor walk-throughs

Each day follows a free GitHub Skills exercise in your own GitHub account. GitHub Actions checks each step as you go, and the founder walks through it live.

01Week 0, togetherWeek 0 lecture and problem set
02Your first C programWeek 1

Dates and times: Dates, times and seats: To be announced. How the live sessions work

Checked on: CS50x, CS50x weeks (2026-11-03). Units listed in the provider's own words; the summary, pace and walk-throughs are ours.

All tracks