Definition
An operating system (OS) is system software that manages a computer’s hardware resources and provides the environment in which applications run, covering process scheduling, memory management, file systems and device drivers.
How it works
The kernel schedules CPU time and memory, maintains the file system, and operates hardware through device drivers; applications request these services via system calls rather than touching hardware directly.
Usage
Windows, macOS and Linux on personal computers, Linux on servers, and Android and iOS on phones are typical environments for operating systems.
Related and confusable terms
An operating system is the general system-software layer, whereas WASM is a sandboxed, portable execution environment sitting on top of it. A virtual machine differs in that it emulates an entire computer, into which another operating system can even be installed.