How Operating Systems Work

What Is an Operating System?

Windows 11
A Windows 11 logo is seen on a smartphone screen with a Microsoft website in the background. Windows is probably the most common operating system. Pavlo Gonchar/SOPA Images/LightRocket via Getty Images

Not all computers have operating systems. The computer that controls the microwave oven in your kitchen, for example, doesn't need an operating system. It has one set of tasks to perform, very straightforward input to expect (a numbered keypad and a few pre-set buttons) and simple, never-changing hardware to control. For a machine like this, an elaborate operating system would be unnecessary baggage, driving up the development and manufacturing costs significantly and adding complexity where none is required. Instead, the computer in a microwave oven simply runs a single hard-wired program called an embedded system all the time.

For other devices, an operating system creates the ability to:


  • Serve a variety of purposes
  • Interact with users in more complicated ways
  • Keep up with needs that change over time

All desktop computers have operating systems. The most common are the Windows family of operating systems developed by Microsoft, the Macintosh operating systems developed by Apple and the UNIX family of operating systems developed by a whole history of individuals, corporations and collaborators. There are hundreds of other operating systems available for special-purpose applications, including specializations for mainframes, robotics, manufacturing, real-time control systems and so on.

In any device that has an operating system, there's usually a way to make changes to how the device works. This is far from a happy accident; one of the reasons operating systems use portable code rather than permanent physical circuits is so that they can be changed or modified without having to scrap the whole device.

For a desktop computer user, this means you can add a new security update, system patch, new application or even an entirely new operating system rather than junk your computer and start again with a new one when you need to make a change. As long as you understand how an operating system works and how to get at it, in many cases you can change some of the ways it behaves.

Regardless of what device an operating system runs, what exactly can it do?