What is a computer? You might picture the one on a desk at school — a screen, a keyboard and a mouse. But a computer is really just a machine that follows instructions to do a job for you. And once you know what to look for, you'll spot computers absolutely everywhere.
Every computer, from the giant ones that predict the weather to the tiny one hiding in a washing machine, does the same four things. It takes in some input, does some processing (the thinking), gives back some output, and it can store things to use later. Learn these four words and you understand the heart of every computer on the planet.
Long before electricity, back in the 1830s, an inventor called
Think about playing a game. You press the buttons — that's the input. The computer works out what should happen — that's the processing. The picture and the sounds come out on the screen and speakers — that's the output. And your high score gets saved so it's still there tomorrow — that's storage.
Here is the same idea drawn as a machine. Step through it and watch each job light up.
Input goes in, processing does the thinking in the middle, output comes out, and storage sits underneath, keeping things safe for next time. Almost anything a computer does is really just these four jobs happening over and over, very, very fast.
The parts you plug into a computer mostly do one of two jobs. Input parts let you put information in. Output parts let the computer send information back out to you. Here are some you'll know:
A few clever parts do both. A touchscreen shows you a picture (output) and feels your finger tap (input). Isn't that neat?
In a way — yes! When you tap a touchscreen, your finger is how the information gets in, so it's doing the job of an input. Your eyes are how the picture gets to your brain, so they're catching the output. A computer only feels useful when its inputs and outputs connect up to a person — that's you!
Every computer is made of two very different things, and telling them apart is one of the most useful ideas in all of computing.
Hardware is the physical stuff — the parts you can actually touch. The screen, the keyboard, the mouse, the speakers, and the powerful little chip deep inside called the CPU (its "brain") are all hardware. If you could pick it up or knock on it, it's hardware.
Software is the instructions — the programs that tell the hardware what to do. A game, a drawing app, a web browser: those are all software. You can't hold software in your hand. It's more like the rules of a game — real and important, but not something you can touch.
The two need each other. Hardware with no software is like a games console with no game — it just sits there. Software with no hardware is like the rules of football with nobody to play them. Put them together and the computer springs to life.
Don't muddle up an app with the thing it runs on! When you play a game on a phone, the game is software — but the phone itself is hardware. You can delete the game and the phone is still there in your hand; the game was never really a thing you could touch.
And here's the sneaky part: loads of everyday objects have a hidden computer inside, running its own software. A washing machine, a microwave, a smart TV, even some doorbells — they all have a tiny computer quietly doing input → process → output → store. If it follows instructions to do a job, there's a computer in there somewhere!
Once you know the four jobs, you can play a brilliant game: spot the hidden computer. Take a washing machine. You choose a wash setting (input). Its little computer works out how long to spin and how hot to make the water (processing). It fills, washes and spins the drum (output). And it remembers the setting you picked (storage). A computer — in a washing machine!
Here are just a few everyday things that are secretly computers:
Way more than you'd guess! If you count everything with a hidden computer — the TV, the games console, phones, tablets, the microwave, the washing machine, maybe a smart doorbell or a robot vacuum — a typical home can easily have twenty or more. And they're not all screens with keyboards. Most computers in the world don't look like a computer at all.