Week 1 · Getting Started

Session 3: Variables and Serial output

Teach & build120 minLesson 04: Sketch Structure, Variables & Types

Learning outcomes

Declare, assign and print variables with Serial.print and Serial.println
Use const for pin numbers and fixed values
Explain global and local scope in a sketch
Predict a sketch's Serial output before running it

Kit and components

Uno, USB cable and lab PC
Serial Monitor at 9600 baud

Pre-reading about 20 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: setup, loop and upload
0:1025 min
Demo
Variables change, constants do not
Live-code a counter printed from loop(). Students predict each line before you run it. Then move the declaration inside loop() and show the counter reset every pass.
0:3525 min
Build
Worked sketch on the board
Students upload the lesson's worked sketch, change one constant and one variable, and record the new Serial output in the logbook.
1:0045 min
Code Along
Variables
Pairs share a PC for the first exercise, then work individually.
1:4515 min
Wrap-up
Predict the output
Project a six-line sketch. Students write its Serial output on paper before you run it.

Checkpoint: ready to move on?

Students can declare an int and a const, print a labelled value on one line, and explain why a variable declared inside loop() resets every pass.

Extension for fast finishers

Catch-up path

Repeat the first variables exercise with the hints open, concentrating on print versus println.

Code Along 2.1: One variable, one label

Homework and practice

Code Along 2.3 and 2.4.

Facilitator notes

Beginners mistype more than they misunderstand. Let the compiler messages teach and avoid fixing code for students.
Code Along compares Serial output exactly - capital letters and spaces matter.