# Operating System Kernel
An operating system kernel is the core of an Operating System.
Examples:
- Linux
- Windows NT
- XNU
Generally, you cannot use a kernel directly since you need an OS, i.e. a software which will mediate communication between you and the kernel.
Example:
- Ubuntu mediates between you and Linux.
- Windows mediates between you and Windows NT.
- MacOS mediates between you and XNU.