Learning objectives
By the end of this week you can:
- 1 Describe the structure of the course: CS50 lecture at home, lecture and lab on Monday, a project of your own.
- 2 Explain the grading: midterm 40%, final 60% (of which 15% is the semester project), and how labs are tracked.
- 3 Set up the three accounts you need: edX (CS50x 2026), GitHub, and Classroom 50.
- 4 State the input → algorithm → output model of computation in your own words.
★ the wow moment
The phone in your pocket has more computing power than all of NASA had in 1969.
The Apollo Guidance Computer ran at about 1 MHz with 4 KB of RAM. A mid-range phone today has several cores at 2–3 GHz and gigabytes of memory. What changed is not the idea, which is the same input → algorithm → output, but the scale. This course teaches the idea; scale is what industry adds on top.
What happened on Monday, September 21
The first meeting was the introduction: who we are, what the course is, and how the semester runs. This page is the written version, for anyone who missed it and for everyone to come back to.
The one question
Everything a computer does, from a text message to a self-driving car, comes down to this:
A computer has no idea what a photo, a song or a word is. It has electricity that is either on or off, which we call 1 and 0. The whole course is the story of how we build everything else out of that.
How the course runs
| When | What | Where |
|---|---|---|
| Before Monday | Watch the week’s CS50 lecture (link on the week page), read the notes, skim the slides | at home, edX or YouTube |
| Monday 13:30–14:45 | Lecture: the ideas, deeper and faster because you have watched CS50, with live coding and industry examples | B101 |
| Monday from 15:00 | Lab: you write code, mostly in C, with autograded feedback. You can start before the instructor arrives; the lab page tells you everything | YM LAB |
| After class | Finish and push the lab, then watch next week’s CS50 lecture | anywhere |
The official slot is 13:15–17:00. We start the lecture at 13:30.
What you need before week 2
- A GitHub account (free). Choose a username you would put on a CV.
- Accept the invitation to the course organization on GitHub (arrives by email).
- Sign in once to Classroom 50.
All three steps are in the lab setup guide. Ten minutes, no installation.
Grading, briefly
- Midterm (week 8): 40%.
- Final: 60%, made of the final exam (85% of that) and the semester project (15% of that).
- Labs: autograded, tracked, and the practice ground for everything else. A student who does every lab has never failed this course.
- The semester project framework is published in week 2. You receive your personal project in week 5, you build until week 15, you demo on the last Monday.
The road ahead
| Weeks | Module | You will |
|---|---|---|
| 1–2 | Foundations | See how everything becomes bits; program in Scratch |
| 3–4 | The C language | Write real programs: variables, loops, functions, arrays, strings |
| 5–8 | Algorithms, memory, data structures | Search, sort, use pointers, build linked lists and hash tables; midterm in week 8 |
| 9–11 | Python, AI and data | Do in ten lines what took fifty in C; understand LLMs; query databases |
| 12–13 | The web | Build a page with HTML, CSS and JavaScript; see how the Internet moves it |
| 14–15 | Humans and projects | Design for people; demo your project |
Summary
- Computer science is about representing and processing information. Computation is input → algorithm → output.
- CS50 at home, lecture and lab on Monday, a project of your own. Labs in C first.
- Before week 2: GitHub, the org invitation, Classroom 50. Then watch CS50 Week 0 (on the week 2 page).
In industry
-
Software runs everything
Banks, hospitals, cars, planes, elections. Understanding how software is built is now basic literacy for any engineer, whatever you end up designing.
-
GitHub is the CV
From week 2 your labs live on GitHub. By December you have a public record of working code, which is exactly what recruiters look at.
-
AI writes code too
Tools like GitHub Copilot and ChatGPT generate code. They make the people who understand code more valuable, not less. That is who this course produces.
Go deeper
- CS50x 2026 course home · Bookmark it. Every week we name the lecture to watch.
- This is CS50 (YouTube playlist) · All lectures, public.
- Lab setup guide · GitHub, Classroom 50 and Codespaces in ten minutes. Do it before week 2.
Tags:introductionsyllabuscs50computational thinking