A computer operating system (OS) is software that manages a computer's hardware and software resources. It acts as an intermediary between users and the computer hardware, allowing users to run applications and perform tasks. Common examples of operating systems include Windows, macOS, and Linux. The OS is responsible for managing files, controlling peripheral devices, and ensuring that different programs can run simultaneously without interfering with each other. It provides a user interface, which can be graphical or command-line based, making it easier for users to interact with the computer and access its features.