How Code Runs: Interpreters, Compilers and the CPU
Python Programming 2 Grades 9–12 3-day lesson 25 deliverables Teach students what happens between the Python code they type and the work the computer does. Students name the kind of error in five short programs, decide when Python finds it and count how many lines print. Pairs then act out a made-up CPU that fetches, decodes and executes, and sort five languages by how they run. Students also fix a sign-up program with two bugs.
● Instant download · Lifetime access · Editable & print-ready
Print + digitalPDF, PowerPoint, Word & Google
Answer keysA key for every page
Built-in assessmentExit tickets + lesson quiz
45-minute daysEvery day planned and timed
Short coding levels practice this lesson in CodeGrove, our code lab that runs in the browser. Students write the program, run it and check it, with no account and nothing to install. Use them with the lesson or as practice later.
See the levelsWhat does this lesson cover?
Students may expect every bug to show up the same way, but a syntax error prints nothing while a runtime error prints the lines before it. This lesson has them predict what prints and then connects bytecode, the interpreter and the CPU.
The try-it on Day 1 and the quiz task on Day 3 run online in CodeGrove, our in-browser code lab, so students need a computer or tablet on those days. The 7.3 Try It level practices fixing a SyntaxError that stops a whole program and catching a ZeroDivisionError that stops a program at its line. CodeGrove is free, with no accounts, sign-ins or installs.
When Is It Caught?
Students name the kind of error in five short programs, when Python finds it and how many lines print, on paper with computers closed.
Everything that's included
00 Start Here
- READ FIRST: every file in the lesson and when you use it
- Teacher Guide and Pacing: the plan for each day, what to print and how to grade
- Skills map: which standards each day teaches
01 Present
- One editable PowerPoint deck for all three days, 27 slides, with speaker notes
- Slide script: the speaker notes, printed
- Bell ringers: a short warm-up for each day
02 Student Handouts
- Guided notes: one packet for all three days, in PDF and editable Word. Students fill in the blanks during the slides, with the word bank on the page
- Vocab slip: the lesson's words and what they mean, on one page
04 Activities
- When Is It Caught?: students name the kind of error in five short programs, when Python finds it and how many lines print, on paper with computers closed
- Be the CPU: pairs act out a made-up CPU on a register board, then sort five languages by how they run, on paper with computers closed
- Quiz task: students fix a sign-up program with two bugs in CodeGrove, then take the lesson quiz on paper
05 Assessment
- Exit tickets: quick questions that show who needs more help
- Lesson quiz: 8 multiple-choice questions and 2 written answers about all three days, on paper
06 Answer Keys
- 5 answer key files: a key for each day (its bell ringer, notes and exit ticket) and the activity keys, plus the quiz key
Digital: Google Forms™ + Google Slides™
- 4 Google Forms™ of the exit tickets and the quiz, ready to copy into your Drive
- The multiple choice grades itself, and you grade the written answers
- A Google Slides™ copy of the deck, with the same slides and speaker notes, for Google Classroom™
- Give a Form that asks students to read code only on school-managed Chromebooks in locked mode, and use the paper version on other devices
Online: CodeGrove
- In CodeGrove: the quiz task on Day 3, on a computer or tablet for each student
- A try-it on Day 1: students practice the new code in CodeGrove, and nothing is turned in
- Free to use, with no accounts, sign-ins or installs
Why teachers love this lesson
The timing of an error tells students its kindPython translates the whole file to bytecode first, so a syntax error stops everything and a runtime error stops at its line.
A CPU works in tiny stepsIn Be the CPU, a made-up CPU with a register board shows how each instruction is fetched, decoded and executed.
Print and digitalEvery page is a print-ready PDF, and the Google Forms™ and Google Slides™ let you teach the same lesson in Google Classroom™.
Real online labsStudents write and run real Python in CodeGrove, our in-browser code lab, on a computer or tablet, with no accounts or installs.
A key for every pageEvery day has its own answer key, and every written question has a sample answer and what to look for.
Every day fits a 45-minute classEach day's plan is timed activity by activity against real reading and writing speeds.
What Teachers Say
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How do I get the files after I buy?
Instant download right after checkout: PowerPoint and Word files you can edit, print-ready PDFs, and links that copy the Google Forms™ and Google Slides™ into your Drive.
Can I buy the whole unit or course instead?
Yes. This lesson is part of the Unit 7 bundle and the complete Python Programming 2 course. Both cost less than buying the lessons one at a time.
Is this AP Computer Science?
No. It is a full-year, non-AP second course in Python for grades 9 to 12. For AP, see our AP Computer Science A and AP CSP courses.
What should students know before this lesson?
Students know modules and import, functions, and how to read an error's name and line.
Do students need computers?
Yes, on the CodeGrove days. Each student needs a computer or tablet that's online, and CodeGrove needs no account or install. The bell ringers, notes, exit tickets and quiz are on paper.
What formats are the files in?
Every page is a print-ready PDF. The slides are an editable PowerPoint and the guided notes an editable Word file. The exit tickets and the quiz also come as Google Forms™, and the deck as Google Slides™.
Which standards does it cover?
Written for Florida's Intermediate Programming course (9007220). The skills map in the lesson shows which standards each day teaches.