---
title: "Introduce the big O notation"
course: "PY102 · Think like a programmer"
unit: "Algorithm analysis"
lesson: 23 of 40
source: https://open.maestrocollege.edu/think-like-a-programmer/introduce-the-big-o-notation
publisher: Maestro College
---

# Introduce the big O notation

Lesson 23 of 40 in **Think like a programmer** (PY102), unit "Algorithm analysis". An open lesson from Maestro College.

## What the learner will be able to do
- Identify what the variable n represents in Big O notation.
- Describe in simple terms what Big O notation means.
- Identify and compare the common growth rates constant, linear, and quadratic, and how each affects how an algorithm's steps grow with input size.

## Teaching notes
* Focus on three growth rates only: constant, linear, and quadratic. Keep it conceptual and beginner-friendly with no formal math.
* The lesson includes an important VIDEO that delivers much of the material; give brief context, then show it early in the session.

## Course teaching approach
- Start from a real-world problem, then introduce the concept as the solution.
- Keep it true beginner level, hands-on, a little gamified. The learner should feel they are winning.
- Balance explanation, demonstration and practice. No copy-paste exercises: give small story-based tasks.
- End with one fun closed question about the topic.

## How to use this document
You are acting as a tutor for a learner on Maestro Open. Teach from this document, one small step at a time. Ask the learner to try things, wait for their answer, then give feedback. Keep it beginner-friendly. If the lesson involves code or spreadsheets and you cannot run them, ask the learner to try it on their own computer and paste the result back. Do not award grades, credit or certificates.

## When the lesson is done
The lesson is complete only when the learner has shown they can do every outcome listed above. Check each one with a small task or question; if an answer is wrong, explain and let them try again before moving on.
When every outcome is covered:
1. Say clearly: "Lesson 23 complete: Introduce the big O notation."
2. Give a two-line recap of what they learned.
3. Name the next lesson, "Analyzing algorithms with big O" (lesson 24 of 40), and give the learner its link: https://open.maestrocollege.edu/think-like-a-programmer/analyzing-algorithms-with-big-o.md. Tell them to paste that page into this chat, or fetch it yourself if you can open links, then start it the same way. Do not start teaching the next lesson's topic until the learner has it.

Previous lesson: Complexity, what it means and why it matters
Next lesson: Analyzing algorithms with big O