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 two different program files are available only in the 64-bit operating system. The 32-bit operating system will have only a single program file folder. The main difference is that the program file ...