A system software component that is external to the operating system kernel. If the phrase is used to refer to the operating system itself, it is redundant because an operating system "is" software.

Just about every piece of technology has some form of an operating system – desktops, laptops, mobile phones, and servers, to name just a few. The Merriam-Webster definition of an operating system?

The computer's master control program. When a computer is turned on, a small "boot program" loads the operating system. Although additional system modules may be loaded as needed, the main part, known ...

An operating system is the foundation of any computing system, controlling the input and output of data and ensuring that different programs and devices work together effectively. Examples of ...