Edit - Super User

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

This is not entirely correct. The requirement that hardware access go through the kernel, or that there even be a kernel, is a design decision made in the affirmative on many systems today, but also made in the negative (even to this day) on many simple systems.
– Chris Stratton
Commented Jul 28, 2018 at 0:02
I'm explaining how things are if A) there is a kernel and B) if you are running code on a CPU with user/supervisor mode and an MMU to help enforce that. Yes, there are CPUs and microcontrollers without MMUs or user/supervisor mode, and yes some systems run without using the whole user/supervisor infrastructure. Microsoft's first Xbox was like this - even though a standard x86 CPU with user/supervisor mode, from what I understand it never left kernel mode - the loaded game could do whatever it wanted.
– LawrenceC
Commented Jul 28, 2018 at 0:11
1

The Macintosh System, before MacOS X, was an OS of a general purpose computer, running on general purpose CPU (68000 family, PowerPC) with support for memory protection for decades (except the first 68000 based computers I think) that never used memory protection: any program could access anything in memory.
– curiousguy
Commented Jul 29, 2018 at 2:25

Add a comment |

Correct minor typos or mistakes
Clarify meaning without changing it
Add related resources or links
Always respect the author’s intent
Don’t use edits to reply to the author

create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
put returns between paragraphs
for linebreak add 2 spaces at end
_italic_ or **bold**
indent code by 4 spaces
backtick escapes `like _so_`
quote by placing > at start of line
to make links (use https whenever possible)
<https://example.com>
[example](https://example.com)
<a href="https://example.com">example</a>

formatting help »
answering help »