Kernel mode
- Ring 0 redirects here. Ringu 0 is the title of a 1998 Japanese cult horror film directed by Tsuruta Norio.
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 privilaged and treated as kernel mode and the least privilaged is ring 3 ususally treated as user mode. rings 1 and 2 are rarely used.