Week 3 · Functions, Outputs & Buttons

Session 12: Functions that share values

Teach & buildFlex120 minLesson 08: Functions: Naming & Reusing Tasks

Learning outcomes

Explain why parameters are copies and local variables are temporary
Use pass-by-reference when a function must change the caller's variable
Split a long loop() into named steps without changing behaviour

Kit and components

Four-LED circuit, Uno and lab PC

Pre-reading about 15 min

Students read these on their phones before class. They are listed on the student Before class page.

Session plan

0:0010 min
Recap
Quiz: functions
0:1020 min
Demo
Copies, locals and references
Show a counter that resets because it is local, then a swap that fails with copies and works with references.
0:3040 min
Code Along
Catch up on earlier Code Along
Finish any core Functions exercises not yet done, then any earlier chapters still open.
- Code Along 5.1: celsiusToFahrenheit()
- Code Along 5.2: Write a function from scratch
1:1040 min
Build
Refactor the pattern controller
Students restructure their S10 mini-project into readCommand(), updatePattern() and showPattern(), testing after each step so behaviour never changes.
1:5010 min
Wrap-up
Does loop() read like a plan?

Checkpoint: ready to move on?

Each student's refactored sketch behaves exactly as before, and loop() contains only function calls.

Extension for fast finishers

Write showLevel() from the lesson challenge, or try the Deeper exercises.

Code Along 5.5: Write your own map()Deeper
Code Along 5.6: Swap two variablesDeeperLaptop

Catch-up path

Skip the refactor and finish the core Functions exercises.

Code Along 5.1: celsiusToFahrenheit()

Homework and practice

Pre-reading for S13.

Facilitator notes

Flex session: in a shorter course skip it. Write your own map() and Swap two variables are Deeper exercises, so nothing later depends on them.