Educate in CS

For students, fellow educators, or self-learners.

Explore how computers work, learn to program, and connect the ideas, with notes and practice currently aligned with IB Computer Science.

Code examples in Java and Python

Browse all topics

103

lessons

5

question types

Free

forever, no signup

The big picture

Every computer does the same four things

It takes input, runs a process, produces output, and saves to storage. You type on a keyboard (input), the CPU runs instructions (process), the screen shows results (output), and files are saved to disk (storage). Every topic on this site zooms into one part of this cycle.

Topics

Pick where you'd like to start

Each topic has notes, worked examples, and interactive exercises; most also have a teacher guide, with more being added. Organised by the six layers of the IB Computer Science syllabus, plus cross-cutting topics.

Information Layer

Information

How numbers, text, images, audio, and video are encoded as binary.

2 lessons

Hardware Layer

Hardware

The CPU fetches, decodes, and executes: billions of times per second. Memory, cache, logic gates, GPU, storage.

8 lessons

Programming Layer

Programming Fundamentals

Variables, data types, operators, Strings, exception handling, debugging.

4 lessons

Programming Constructs

Sequence, selection, iteration, methods: the three building blocks of every program.

3 lessons

Data Structures

1D and 2D arrays, ArrayLists, stacks, queues: choosing the right collection.

5 lessons

Algorithms

Searching, sorting, and Big-O notation: picking the right tool for the job.

5 lessons

File Processing

Reading and writing text files in Java and Python: read, write, append, and close safely.

2 lessons

Object-Oriented Programming

Modelling problems as interacting objects: classes, encapsulation, inheritance, polymorphism.

25 lessons

Abstract Data Types

Building structures from scratch: linked lists, stacks, queues, BSTs, hash tables.

10 lessons · HL

JavaFX Cookbook

Plug-and-play JavaFX recipes for building a desktop app: tables, dialogs, file pickers, charts, and more.

13 recipe pages

Software Development

The craft around the code: requirements, design, testing, documentation, and usable interfaces.

5 lessons

Operating Systems Layer

Operating Systems

Scheduling, multitasking, interrupts: how the OS juggles programs and devices.

5 lessons

Applications Layer

Databases

How databases store and query structured data: relations, ERDs, normalisation, SQL.

11 lessons

Machine Learning

How machines learn from data: types of learning, training, evaluation, and neural networks. Stretch pages go further: LLMs, image generation, and AI beyond machine learning.

6 lessons

Communication Layer

Communication

Packets, protocols, architectures, encryption: how devices talk to each other.

6 lessons

Also on the site

Computational Thinking

Decomposition, abstraction, pattern recognition: the thinking that comes before coding.

4 lessons

Ethics & Implications

ML ethics, privacy, bias, surveillance, the digital divide: the responsibilities that come with computing.

2 lessons

IB CS Assessments

Internal Assessment

The 30-mark IB CS project: criteria, planning, development, evaluation.

8 pages

Case Study

The 2027 case study, Generative AI for image creation: techniques, models, ethics, and exam strategy for Paper 1 Section B.

8 pages

CS Extended Essay

A 4,000-word independent research essay in computer science: choosing a topic, framing a question, evaluating sources.

6 pages

Practise as you learn

Five ways to practise

Each card opens one on a real lesson, Iteration (Loops).

✓ Adjacent elements

First and last

Quick Check

Choose an answer and read the explanation.

i   j   arr[j]

0   0   5

0   1   _

Trace Exercise

Follow the code line by line and record how the variables change.

for (int i = 0;

     i < n;

     i__) {

Code Completion

Fill the blanks in a method or loop until the code works.

for (int i = 0; i <=

   arr.length; i++)

  sum += arr[i];

Spot the Error

Find the error and choose the correction.

x = 5

x *= 2

print(x)

→ 10

Predict the Output

Read the code, predict its output and check your answer.

Study tools

Tools for studying

• Key Conceptsclear explanations with precise terminology
• Worked Examplesstep-by-step solutions
• Practice ExercisesCore, Extension, and Challenge levels
• Glossary Tooltipshover over or tap a highlighted term for its definition
• Connectionsprerequisites and related topics to explore next
• GitHub Classroomprogramming assignments with automated tests
• My Progresskeep track of reviewed pages and quiz scores in this browser on My Progress
• Works Offlineinstall the site as an app; pages you have visited stay readable without a connection