The primary purpose of an operating system (OS) is to manage and facilitate communication between hardware and software components of a computer system. It provides a user interface, allocates system resources, manages file systems, and facilitates the execution of applications. Essentially, the OS acts as an intermediary between users and the computer hardware.

Examples of popular operating systems include:
1. Microsoft Windows
2. macOS (formerly OS X)
3. Linux distributions (such as Ubuntu, Fedora, and Debian)
4. Android (for mobile devices)
5. iOS (for Apple mobile devices)

Each of these operating systems serves specific platforms and user needs.