Putting It All Together: From Big Problem to Small Commands You have learned the core skill of this series. Let us see it in action — fully, from start to finish. What You Learned Post The Big Idea ------ ------------- What is Decomposition? Breaking a big problem into smaller pieces that are each easier to understand and act on Decomposition in Everyday Life You already do this constantly — getting ready, cooking, travelling Why Computers Need Small Steps Computers follow one specific instruction at a time — big vague goals are not instructions A Complete Example: Making a Cup of Tea Let us take one real goal and decompose it all the way down to the level of commands a computer could follow. The Goal > "Make a cup of tea" First Level of Decomposition 1. Boil the water 2. Prepare the cup 3. Brew the tea 4. Add milk and sugar if needed Better — but these are still too big. Let us go deeper. Full Decomposition Boil the water: 1. Fill the kettle with cold water (at least 300ml) 2. Place the kettle on its base 3. Press the On button on the kettle 4. Wait until the kettle clicks off (water is boiling) Prepare the cup: 5. Take a clean mug from the cupboard 6. Place one tea bag into the mug Brew the tea: 7. Pour the boiling water into the mug, filling it to about 2cm from the top 8. Wait 3 minutes (letting the tea brew) 9. Remove the tea bag by pressing it gently against the side of the mug with a spoon 10. Discard the used tea bag Add milk and sugar: 11. If milk is desired: pour approximately 50ml of cold milk into the mug 12. If sugar is desired: add one teaspoon of sugar 13. Stir the tea for 10 seconds The Result: 13 specific, exact commands Each one is: ✅ Specific (only one correct way to carry it out) ✅ Achievable (a robot or programme could do this step) ✅ In the right order (changing the order would break things) "Make a cup of tea" is now a programme. The Decomposition Checklist When breaking down any problem, ask: 1. What are all the things that need to happen? (List them) 2. Is each step specific enough to act on? (Or does it need more breaking down?) 3. Are the steps in the right order? (Would changing the order break anything?) 4. Are there any steps I assumed, but did not write? (Computers cannot assume) Run through these questions for every decomposition before calling it done. Why This Matters for Everything Ahead You now have two powerful skills: 1. Commands — you know what an individual instruction looks like and what makes it good 2. Decomposition — you know how to break any goal into a sequence of those instructions Together, these let you take any real problem and work out what commands are needed to solve it. But there is still one question we have not answered: What actually starts those commands running? You press a button. The door opens automatically. Your alarm goes off at exactly 7:30 AM. Something triggers the sequence of commands to begin. Those triggers are called events — and they are what the next series is about. ✅ Summary Decomposition turns big goals into sequences of specific, achievable commands. It can go multiple levels deep — "boil the water" can itself be decomposed into 4 steps. The result is a programme: an ordered list of precise instructions that together achieve the original goal. Every real programme was designed this way — starting from a goal, decomposing it into smaller pieces, and continuing until every step is specific enough to execute. You now know how to think about problems the way programmers do. Coming up next in the series: Events and Responses — what triggers your carefully decomposed commands to run, and how computers respond to things happening in the world.