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Jun 1, 2021 at 14:25 comment added Peter - Reinstate Monica Well, I'd say managing access to disks -- like all the other hardware -- is an operating system's first and most basic function ("DOS" ...). Using that to access files is one abstraction layer removed and may or may not be realized by the operating system. But apart from this nitpick: Proper answer.
Jun 1, 2021 at 13:57 comment added RonJohn Exactly. The raison d'être of an OS is handling this kind of thing for user space...
Jun 1, 2021 at 4:22 comment added Peter Cordes Some of this is x86-centric (e.g. ring 0), but yes, user vs. supervisor/kernel mode is common to all ISAs that support multi-user OSes that can isolate processes from each other, and stop them from taking over the machine. Most do just have user vs. kernel, not x86's ring 0 / 1 / 2 vs. ring 3, which is part of why mainstream / portable OSes don't use ring 1 or 2 them even on x86. (And they normally put the CPU into long mode; 32-bit kernels are obsolete except for really old hardware.)
Jun 1, 2021 at 4:15 review First posts
Jun 7, 2021 at 21:17
Jun 1, 2021 at 4:12 history answered Alex Cannon CC BY-SA 4.0