What an operating system does — Computing, 14–17 years
An operating system is the organiser between programs and hardware. It shares the processor, memory and devices, while giving programs safer, simpler ways to ask for what they need.
The organiser underneath
An operating system sits between applications and the machine's hardware. It decides which program gets processor time, gives programs areas of memory, manages files and talks to devices such as keyboards and screens. This lets an app request a file without knowing the exact electronics involved.
Why an operating system appeared
Without an operating system, every program would need its own instructions for each printer, disk and screen. Programs could also overwrite one another's memory. Operating systems grew from the need to share expensive hardware, hide unhelpful details and stop one program from ruining another.
Opening two apps
Suppose a music player and a browser are open. The operating system gives the player some processor time, then lets the browser run, switching quickly between them. It keeps each app's memory separate and sends sound to the speakers while sending the browser's picture to the screen.
The operating system is not every app
It is easy to think that the operating system is simply whatever appears on the screen, because its menus and icons are visible. Much of its work is hidden: scheduling, memory protection and device control. A browser or game uses those services, but it remains a separate program with its own purpose.
Where it shows up
Phones, laptops, game consoles, cars and many household devices use operating systems. When a phone asks permission to use the camera, or when a laptop lets two programs share a printer, the operating system is involved. Choosing a lighter system can also leave more resources for demanding applications.
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