Which of these is system software?

The correct answer is Windows OS, as it is a prime example of system software. System software serves as a bridge between the hardware of a computer and the application software that users interact with. It manages hardware resources and provides a platform on which applications can run. The Windows operating system is designed to manage hardware, provide user interfaces, and support software applications, making it an essential type of system software.

In contrast, CPU refers to the hardware component that processes instructions, not software. BIOS (Basic Input/Output System) is indeed system software, but it operates at a lower level during the boot process and is not as widely recognized by end-users as an operating system like Windows. A text editor, while useful as application software, does not fit into the category of system software, as it is intended for creating and editing documents rather than managing system resources.