Kernel mode

Ring 0 redirects here. is the title of a 2000 Japanese cult horror film.

In processors with memory protection, kernel mode or privileged mode (as opposed to user mode) is the mode in which the operating system kernel runs. Code running in this mode has unlimited access to the system memory and external devices.

Microkernel operating systems attempt to minimize the amount of code running in privileged mode, for security and elegance reasons.

The x86 architecture is unusual in having four privilege levels, of which the most privileged, ring 0 is the most privileged and treated as kernel mode and the least privileged is ring 3 usually treated as user mode. rings 1 and 2 are rarely used.