How a computer is built from switches
From a single on or off all the way to a whole computer, we've come a long way. This lesson isn't for learning something new; it's for seeing, at a glance, how the road so far fits together.
The road so far
At first there was only on and off.
We gathered those into decisions, gathered decisions into addition, added a way to remember, and tied it all together into a CPU.
Tap each stop below and you can recall what we did there.
From a switch to a whole computer: the road we traveled.
Each stop may have felt a little hard at the time.
But gather them together and they're all connected.
One small switch became a decision, then a calculation, and finally a whole computer.
How a switch becomes a computer
The amazing part is that all of this was built up from a single on or off.
Press the build button below to see, all at once, how one switch grows into a computer.
Switch → gate → adder → CPU → a whole computer.
There's no grand magic.
Gather small things, then gather more on top: this way of stacking things up is the secret behind the computer.
Even things that look complicated are really towers of simple pieces.
Which part was it?
This isn't a test, just a light chance to recall.
For each question, tap the answer you think is right.
It's fine if you don't remember. You can always scroll back up and look again.
Tap the answer you think is right and you'll see right away if it is.
If it came back to you, it's already yours.
If it didn't, that's fine too.
More important than the names is the feeling that small things come together to make big things.
From the bottom up
Here's the whole thing on one page.
At the very bottom are on and off, above them decisions, above those calculation and memory, above those the CPU, and at the very top a whole computer.
It's a single tower, each layer holding up the one above.
Each layer holds up the one above it.
So when computers feel hard, just go down one layer at a time.
At the very bottom there's always something simple: on and off.
Complexity is just things stacked up.
Where to next
That's the body of a computer.
We built it with our own hands, from a switch to a whole machine.
How this body thinks and moves is waiting in the next section.
You did a great job.
The body is built; now for what comes next.
We hope a computer is no longer a mysterious black box.
Inside it are on and off, and the human ideas that stacked them up.
See you in the next section.