Ring 0 is one of the
privilege levels[?] in which an
x86 processor can operate at any time. The others are rings
1[?],
2[?] and
3[?]. Of these most of the
operating systems including
Linux use only two levels, namely Ring 0 and Ring 3. Ring 0 is the highest privilege level and is the level at which the
operating system kernel runs (kernel mode). Ring 3 is the lowest privilege level and is the level at which user
applications are run.
Ring 0 is also the title of a Japanese film directed by Tsuruta Norio[?]. See Ring 0 (movie)[?].