Lesson 3 of 5 · about 20 minutes

What an operating system does

🏠The everyday picture

A school has teachers, classrooms, a library and a playground. The school office decides which class uses which room, keeps the register, rings the bell and checks visitors at the gate. Nobody notices the office when it works well, but without it the school would stop. A computer's operating system is its school office.

📘What it really is

The operating system (OS) is the main program that runs the whole computer. Other apps ask it for what they need. It:

shares the processor and memory between the apps you have open;
looks after files and folders on storage;
talks to the hardware: screen, keyboard, Wi-Fi, printer, camera;
keeps users apart and safe: logins, passwords, and which app may use the camera or your location;
installs updates that fix problems and close security holes.

Common operating systems:

On	Operating systems
Laptops and desktops	Windows, macOS (Apple), Linux (many versions, such as Ubuntu)
Phones and tablets	Android, iOS and iPadOS (Apple)
Web servers	Mostly Linux

An app (application) is a program that runs on top of the OS: a browser, WhatsApp, Excel. The same app is built separately for each OS, which is why some apps exist for Android but not for iPhone.

📝A worked example

You open the camera in a video-call app for the first time. The app can't switch the camera on by itself: it asks the OS. The OS shows "Allow this app to use the camera?" and waits for you. If you tap Don't allow, the OS keeps the camera off for that app. That's the OS doing its job of keeping you safe.

🖱️Try it

Find out which operating system and version you have:

Windows: Settings, then System, then About (look for "Windows specifications").
Mac: Apple menu, then About This Mac.
Android: Settings, then About phone, then Android version (on Samsung phones, About phone, then Software information).
iPhone: Settings, then General, then About.

Then look at the app permissions: on Android, Settings, then Apps, choose an app, then Permissions; on iPhone, Settings, then Privacy & Security. Is there any app with camera or location access that doesn't need it?

✅Quick check

Is WhatsApp an operating system?

Show the answer

No. It's an app that runs on top of an operating system (Android or iOS). It asks the OS for the camera, the network and storage.

Why does an app ask permission before using your location?