Operating system

Group of computer programs, including device drivers, kernels, and other software that lets people interact with a computer. It manages computer hardware and software resources. It provides common services for computer programs.

An OS can be small (like MenuetOS), or large (like Microsoft Windows, GNU/Linux). Different operating systems can be used for different purposes. Some are used for everyday things like on a personal computer (general-purpose). Others are mobile operating systems or are used for specialized work.
— Simple English Wikipedia

I use the following operating systems:

• Linux kernel based operating systems
• Android linux kernel based operating system
• MS Windows NT kernel based operating system

References

• Operating Systems: Crash Course Computer Science #18
• Computer Basics: Understanding Operating Systems
• Computer Basics: Understanding Operating Systems
• Operating System Tutorial