Harvard CS50 (2025)
COMPLETE Weeks 1-12
MASTERY BUNDLE –
Problem Sets, Lecture
Notes, Code Samples &
Exam Prep | C, Python,
SQL, JavaScript + Bonus
Cheat Sheets | 400+ Pages
of Notes, Week-by-Week
,Cheat Codes,
Cybersecurity Labs & AI
Implementation Examples
+ Expert Rationales
Table of Contents
• Week 1
• Week 2
• Week 3
• Week 4
• Week 5
• Week 7
• Week 8
• Week 9
• Week 10
Week 12
,Week 1
Andrew Sellergren
Table of Contents
Announcements and Demos
From Last Time
From Scratch to
C hello, world!
Linux
Commands
Compiling
User Input
Loops
Announcements and Demos
•
Next time you’re milling about the Science Center, take a
gander at the Mark I, one of the very first electromechanical
computers capable of long self-sustained computation. Check
out this giant calculator. From this same Mark I computer comes
the term "bug" that we take for granted. One of the engineers
discovered an actual moth in the machine
that was causing some incorrect calculations. The moth was then
taped
to a log book for posterity’s sake.
•To help make the class feel a bit more intimate, we’ll be gathering most
Fridays at Fire and Ice in Harvard Square for a casual lunch. If
you’re interested, RSVP here.
•
Avail yourself of the following resources at cs50.net/lectures to
aid you in your quest through CS50:
, o videos
If you click the icon at the bottom right in the video player,
you’ll see a searchable full transcript of the lecture.
o slides o examples o walkthroughs
To illuminate some of the more complex examples
from lecture, we offer walkthroughs of those
examples. Check out
the first round here.
o scribe notes
Welcome to the scribe notes! This is your canonical
source of notes for each lecture so that you don’t
have to scribble down anything while listening to
David. This is also your
canonical source for jokes made at David’s expense.
• Sectioning starts Wednesday. This Sunday [1] we’ll offer a one-
time supersection led by the course heads and available on video
afterward.
• It’s time to introduce our inimitable course heads: Lauren
Carvalho, Rob
Bowden, Joseph Ong, R.J. Aquino, and Lucas Freitas. Feel free to
reach out to them at .
• Problem Set 0 has been released!
• Office Hours will begin soon! There really are no dumb questions.
[2]
• CS50 Discuss is the course’s forum where you can post any and all
questions you have. We’ll monitor it during lecture so that if you
have a question about something David says, you can post it and
we’ll try to
respond in realtime.
• If you come into this course with little or no prior background in
computer science or you’d just like to have the safety net of being
able to call it quits when you’re 90% done with a problem set on a
COMPLETE Weeks 1-12
MASTERY BUNDLE –
Problem Sets, Lecture
Notes, Code Samples &
Exam Prep | C, Python,
SQL, JavaScript + Bonus
Cheat Sheets | 400+ Pages
of Notes, Week-by-Week
,Cheat Codes,
Cybersecurity Labs & AI
Implementation Examples
+ Expert Rationales
Table of Contents
• Week 1
• Week 2
• Week 3
• Week 4
• Week 5
• Week 7
• Week 8
• Week 9
• Week 10
Week 12
,Week 1
Andrew Sellergren
Table of Contents
Announcements and Demos
From Last Time
From Scratch to
C hello, world!
Linux
Commands
Compiling
User Input
Loops
Announcements and Demos
•
Next time you’re milling about the Science Center, take a
gander at the Mark I, one of the very first electromechanical
computers capable of long self-sustained computation. Check
out this giant calculator. From this same Mark I computer comes
the term "bug" that we take for granted. One of the engineers
discovered an actual moth in the machine
that was causing some incorrect calculations. The moth was then
taped
to a log book for posterity’s sake.
•To help make the class feel a bit more intimate, we’ll be gathering most
Fridays at Fire and Ice in Harvard Square for a casual lunch. If
you’re interested, RSVP here.
•
Avail yourself of the following resources at cs50.net/lectures to
aid you in your quest through CS50:
, o videos
If you click the icon at the bottom right in the video player,
you’ll see a searchable full transcript of the lecture.
o slides o examples o walkthroughs
To illuminate some of the more complex examples
from lecture, we offer walkthroughs of those
examples. Check out
the first round here.
o scribe notes
Welcome to the scribe notes! This is your canonical
source of notes for each lecture so that you don’t
have to scribble down anything while listening to
David. This is also your
canonical source for jokes made at David’s expense.
• Sectioning starts Wednesday. This Sunday [1] we’ll offer a one-
time supersection led by the course heads and available on video
afterward.
• It’s time to introduce our inimitable course heads: Lauren
Carvalho, Rob
Bowden, Joseph Ong, R.J. Aquino, and Lucas Freitas. Feel free to
reach out to them at .
• Problem Set 0 has been released!
• Office Hours will begin soon! There really are no dumb questions.
[2]
• CS50 Discuss is the course’s forum where you can post any and all
questions you have. We’ll monitor it during lecture so that if you
have a question about something David says, you can post it and
we’ll try to
respond in realtime.
• If you come into this course with little or no prior background in
computer science or you’d just like to have the safety net of being
able to call it quits when you’re 90% done with a problem set on a
