What is a computer, really?
A computer takes in information, changes it by following instructions, and gives back a result. Meet the idea behind every phone, game console and laptop.
You use computers all day. Your phone is one. So is a games console, a laptop and the screen at the supermarket checkout. But what is a computer, really? And what makes it so different from a toaster or a bicycle?
The one big idea
A computer is a machine that follows instructions to take in information, change it, and give back a result.
That is the whole trick. Every computer, from a pocket calculator to a huge weather-forecasting machine, does four things:
- Input. Information goes in. You press a key, tap a screen, speak into a microphone, or a sensor measures the temperature.
- Process. The computer works on that information by following instructions.
- Output. A result comes out: letters on a screen, a sound, a printed page, or a motor that starts turning.
- Store. It can remember things for later, in its memory and storage.
Think about typing a message to a friend. The input is your fingers on the keys. The process turns key presses into letters and decides where they go. The output is the words on the screen. The store keeps the message so it is still there tomorrow.
What makes it different from other machines?
A bicycle does one job. A toaster does one job. But a computer can do thousands of different jobs, because its instructions can be changed. The same phone can be a map, a camera, a game and a calculator. All that changes is the instructions it follows.
A computer that can be given new instructions is called programmable. Those instructions are called a program, or software. The physical parts, the things you can touch, are called hardware.
| What it is | Example | |
|---|---|---|
| Hardware | The physical machine | The screen, the chips, the battery |
| Software | The instructions | A game, a web browser, a calculator app |
Computers are fast, but not clever
This is the part that surprises people. A computer does not understand anything the way you do. It follows its instructions exactly, one tiny step at a time. It does not guess what you meant.
What makes it feel clever is speed. A typical computer can do billions of tiny steps every second. Each step is very simple, like adding two numbers or comparing them. But billions of simple steps, in the right order, can show a video, play music, or beat you at chess.
Before electronic machines, a "computer" was a person whose job was to do calculations by hand, for example to work out where ships were or to build tables of numbers. When machines took over this job, they inherited the name.
Computers hide everywhere
You may use many more computers than you think. A microwave, a washing machine, a thermostat, a car (which often has dozens), a TV remote and a smart watch all contain small computers. They take in information (a button press, a temperature), follow instructions, and give back a result (heat, a wash cycle, a beep).
What you will learn next
In this path, we will open the lid and look inside:
- how a machine made of switches can count (bits)
- how letters, pictures and music become numbers
- how switches make decisions (logic gates)
- how the parts work together, and how people give instructions (algorithms and programs)
At the end, you will see why some jobs are too messy for instructions, and why that leads to machine learning.
Words to know
- Computer
- A machine that follows instructions to take in information, change it, and give back a result.
- Hardware
- The physical parts of a computer that you can touch.
- Software
- The instructions, or programs, that a computer follows.
- Program
- A list of instructions for a computer.
- Programmable
- Able to be given new instructions to do a new job.
Check yourself
What four things does every computer do?
Show the answer
It takes in information (input), changes it by following instructions (process), gives back a result (output), and remembers things (store).
What is the difference between hardware and software?
Show the answer
Hardware is the physical machine you can touch. Software is the instructions the machine follows.
Is a computer clever or fast?
Show the answer
It is fast, not clever. It does exactly what its instructions say, but it can do billions of tiny steps every second.
Name three things in your home that contain a computer, besides a laptop or phone.
Show the answer
For example a microwave, a washing machine, a TV, a car, a thermostat, a games console or a smart watch.