Lesson Plan

• Describe what system decomposition is and why it is used.
• Identify the main functions of a problem and group them into logical sub‑systems.
• Define clear interfaces (inputs and outputs) for each sub‑system.
• Produce a hierarchical diagram that shows the relationship between sub‑systems and the overall system.
• Evaluate a decomposition for independence, cohesion and completeness.

• Projector or interactive whiteboard
• Slide deck covering decomposition steps
• Sample problem handout (e.g., library book‑lending system)
• Worksheet for student decomposition activity
• Whiteboard markers
• Laptops with a simple diagramming tool (or paper & pens)

Begin with a quick recall question about modular design to activate prior knowledge. Explain that breaking a complex problem into smaller, manageable parts helps teams work together and makes testing easier. State that by the end of the lesson students will be able to produce a clear sub‑system diagram and justify their design choices.

1. Do‑now (5') – short quiz on modular concepts to gauge understanding.
2. Mini‑lecture (10') – define system decomposition, discuss benefits and design tips.
3. Guided example (15') – walk through the library book‑lending system, identify sub‑systems and their interfaces.
4. Group activity (20') – students receive a new scenario (timetable generator) and create their own decomposition on the worksheet.
5. Pair check (5') – groups exchange work and use a checklist to give feedback.
6. Whole‑class debrief (5') – highlight common strengths and pitfalls, reinforce key terminology.

Summarise how systematic decomposition reduces complexity and supports teamwork. Ask each student to write one “take‑away” sentence on an exit ticket describing how they will apply decomposition in future projects. Assign homework: choose a personal or school‑based problem and produce a sub‑system diagram with inputs and outputs.