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Inside the Machine G3 to G5 / Week 12 / Monday
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Week 12 · Design a computer

Monday

A computer for a purpose
// Pick parts for a purpose
⏱ about 15 min

Monday: A computer for a purpose

A neighbor asks the crew a new kind of question. "I want a computer for my garden. It should tell me when the soil is dry." Rocket grins. "A garden computer! Where do we even start?"

Raven pulls out a blank card. "What do you notice about the question? It tells us the job before it tells us the parts."

Nova hovers over the card. "Would you like a hint? Start with the purpose. The parts will follow."

Rocket and Raven sketch a computer design on a big board. They pick inputs, outputs, storage and power.

Purpose first

Every computer you have met this year was built for a job. A tablet for drawing. A laptop for homework. A tiny computer inside a thermostat.

A designer starts with the purpose. What must this device do? Who will use it? Where will it live?

Only then does the designer pick the parts. The parts are the same seven you know. Input, processor, memory, storage, output, power and network.

The purpose decides how much of each part is needed. A garden computer and a drawing tablet share the same parts in very different amounts.

Match the parts to the job

PartGarden computerDrawing tablet
InputA soil moisture sensorA touchscreen and a stylus
ProcessorSmall and slow is fineFast, to draw smooth lines
MemoryA littleA lot, for big pictures
StorageTiny, a few numbers a dayLarge, for many drawings
OutputOne light or a small screenA big, bright screen
PowerA small battery or a solar panelA battery charged every day
NetworkWi-Fi to send one message a dayWi-Fi for backups and sharing

Look at the table. The garden computer needs almost nothing. One sensor, one light, a tiny battery.

The drawing tablet needs a lot. A fast processor, a big screen and plenty of storage.

Neither one is better. Each one fits its job. That is what good design means.

PICK THE PART
  • Read the question.
  • Tap your answer.
The garden computer must know if the soil is dry. Which input does it need?
A drawing tablet needs smooth lines. Which part matters most?
The garden computer sends one message a day. How much network does it need?
What does a designer decide first, the parts or the purpose?
Which part turns a drawing into light you can see?
Which part keeps the drawings when the tablet is off?
How many parts are in every computer system you learned?
StatementTrue or false?
A garden computer needs a fast processor.?
Every computer has the same seven kinds of parts.?
A drawing tablet needs more storage than a garden computer.?
The best computer has the most of everything.?
WHY THIS EXERCISEGood design means the right amount of each part for the job.
What does a designer start with before choosing parts? One word.
WHY THIS EXERCISEPurpose tells you which parts matter and which ones can be small.
Try it
Find three devices at home that have a computer inside.
For each one, say its purpose in one sentence.
Name one part that is big in it and one part that is tiny.

Great start, Crew Technician! You began with the purpose, like a real designer. Tomorrow you will learn about trade-offs. More of one thing often means less of another.