24wi ver.

Note: this is for the Winter 2024 iteration of CSE 121. Looking for a different quarter? Please visit https://courses.cs.washington.edu/courses/cse121/.

Welcome to CSE 121: Introduction to Computer Programming 🎉

What is this class? What will I learn?

Computing continues to play an ever-increasing role in today’s society. Having an understanding of computing is an essential skill for those in the 21st century; from working in industries more reliant on technology, using computational methods to further scientific understanding, or being an informed citizen in a world with technology all around us.

This course is a first course in computer programming focused on the basics of procedural programming in Java. It assumes students have not taken a previous programming course and do not have substantial other programming experience. (Students with previous experience are encouraged to consider CSE 122.)

Prior Experience and Expectations

Prerequisite Material

To better assess if CSE 121 is the right class for you, the Allen School has developed a Self-Guided Placement to help students assess which intro course is the right one for them to enroll in. Please see this website for more information on who to contact if you have questions about which introductory CSE course is the right course for you.

Programming Language

CSE 121 is taught in the Java programming language. No prior experience in Java is required!


If you want to learn more about the course and its policies, please check out our course syllabus.


Feedback is always welcome! You can contact the the course staff or submit anonymous feedback.


Please do not email the course staff or instructors regarding registration for the course. The course staff do not have access to add codes. Please email ugrad-adviser@cs.washington.edu for assistance.


This Week (at a glance)

Monday (03/11)

  • TA-led Final Review Session (4:30 pm - 6:50 pm in SMI 120)

Tuesday (03/12)

  • Final Exam (12:30-2:20 in KNE 110 and 130) - you've got this :)

Thursday (03/14)



This is a rough sketch of the quarter and things are subject to change. We can accurately predict the past, but predicting the future is hard!


Anything listed in the “Lesson” materials for a day should be read before attending class that day. The Lessons are a first introduction to the most important terms and concepts for that day of class. It is okay if the Lesson doesn’t make complete sense as we have the rest of the class day to clarify the concepts, but if you don’t do the Lesson the class session won’t make any sense.

Topic Programming / Creative Projects Resubmissions
Week 1
Wed 01/03
LES 00 Welcome!; Course Policies

Note: Normally you would complete the Pre-class Work before class. There is nothing you need to complete before class today!

Thu 01/04
SEC 00 Welcome!
resources: materials
Fri 01/05
LES 01 Printing; Turtle Basics
Hello World!
I.S. by 11:59pm PT
Week 2
Tue 01/09
SEC 01 Printing; Turtle Basics
resources: materials
Wed 01/10
LES 02 Datatypes; Expressions
Code Reviews
I.S. by 11:59pm PT
Thu 01/11
SEC 02 Datatypes; Expressions
resources: materials
Fri 01/12
LES 03 Variables; Strings; Debugging
Week 3
Tue 01/16
SEC 03 Variables; Strings; Debugging
resources: materials
Wed 01/17
LES 04 for Loops
Drawing Shapes
I.S. by 11:59pm PT
Thu 01/18
SEC 04 For Loops
resources: materials
Resub 0
C0, P0 Due 11:59pm PT
Fri 01/19
LES 05 Nested for Loops; Random; Math
Week 4
Tue 01/23
SEC 05 Nested For Loops; Random; Math
resources: materials
Wed 01/24
LES 06 Methods; Parameters; Scope
Election Simulator
I.S. by 11:59pm PT
Thu 01/25
SEC 06 Methods; Parameters
resources: materials
Resub 1
C0, P0, C1 Due 11:59pm PT
Fri 01/26
LES 07 Parameters; Return Values
Week 5
Tue 01/30
SEC 07 Returns & Quiz Prep
resources: materials
Wed 01/31
LES 08 Return Values
Social Network
I.S. by 11:59pm PT
Thu 02/01
QUIZ 00 Quiz 0: Printing, Datatypes, Expressions, for Loops, Methods, Parameters, Scope
Resub 2
C0, P0, C1, P1 Due 11:59pm PT
Fri 02/02
LES 09 Conditionals
Week 6
Tue 02/06
SEC 09 Conditionals
resources: materials
Wed 02/07
LES 10 while Loops
Thu 02/08
SEC 10 while Loops
resources: materials
Resub 3
P0, C1, P1, C2 Due 11:59pm PT
Fri 02/09
LES 11 User Input (Scanner)
Prioritizing Patients
I.S. by 11:59pm PT
Week 7
Tue 02/13
SEC 11 Scanner & Quiz Prep
resources: materials
Wed 02/14
LES 12 Putting It All Together

Note: No Pre-Class Material for Today!

in-class: pdf pptx materials
Thu 02/15
QUIZ 01 Quiz 1: Nested for Loops, Random, Math, Methods, Parameters, Return Values, Conditionals, While Loops
Resub 4
C1, P1, C2 Due 11:59pm PT
Fri 02/16
LES 13 Putting It All Together

Note: No Pre-Class Material for Today!

in-class: pdf pptx materials
Week 8
Tue 02/20
SEC 13 TA's Choice!
Wed 02/21
LES 14 Arrays
Dance Dance Arrayvolution
I.S. by 11:59pm PT
Thu 02/22
SEC 14 Arrays
resources: materials
Resub 5
P1, C2, P2 Due 11:59pm PT
Fri 02/23
LES 15 Reference Semantics
Week 9
Tue 02/27
SEC 15 Reference Semantics
resources: materials
Wed 02/28
LES 16 2D Arrays
2DNArray Sequencing
I.S. by 11:59pm PT
Thu 02/29
QUIZ 02 Quiz 2: Conditionals, while Loops, User Input (Scanner), Arrays
Resub 6
C2, P2, C3 Due 11:59pm PT
Fri 03/01
LES 17 Array Patterns
Week 10
Tue 03/05
SEC 17 2D Arrays & Array Patterns
resources: materials
Wed 03/06
LES 18 Final Exam Review

Note: No Pre-Class Material for Today!

Thu 03/07
SEC 18 Final Exam Review; Wrap-Up
resources: materials
Resub 7
All Eligible! Due 11:59pm PT
Fri 03/08
LES 19 Wrap-Up; Victory Lap!

Note: No Pre-Class Material for Today!

Week 11
Tue 03/12
EXAM Final Exam 12:30pm - 2:20pm
Wed 03/13 Finals Week
Thu 03/14 Finals Week