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Jim Henderson wrote:
> On Sun, 04 Jan 2009 10:10:29 -0800, Darren New wrote:
>
>> Xen is an OS
>
> I don't know that I'd agree with that.
Is VM/CMS an OS? I bet IBM would say so. :-)
> A hypervisor is a hardware
> abstraction layer, messing about with the various memory rings in the
> system in order to make the OS running within the hypervisor believe it's
> running in Ring 0 when it's not in order to take advantage of memory
> protection features in the hardware without tripping the native hardware
> up when a child domain bombs out.
Sure. And Linux is a hardware abstraction layer, making your application
think it has a linear RAM address space to mess with and providing linear
sequences of bytes on disk to read and write (organized as a single tree of
names), when none of those are actually true. One of the jobs of an OS is
necessarily abstracting the hardware in *some* way, if you accept that
maintaining state and managing resources between independent applications is
part of the definition of an OS.
Of course you could argue either way. I was more contrasting Xen against a
BIOS than arguing that Xen must necessarily be considered an OS.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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On Mon, 05 Jan 2009 14:43:09 -0800, Darren New wrote:
> Jim Henderson wrote:
>> On Sun, 04 Jan 2009 10:10:29 -0800, Darren New wrote:
>>
>>> Xen is an OS
>>
>> I don't know that I'd agree with that.
>
> Is VM/CMS an OS? I bet IBM would say so. :-)
It's also probably a bit more involved than XEN is. I suppose I could
ask my local XEN expert, was just recalling from a presentation he gave a
few weeks ago at a conference I attended about how XEN actually works.
It's pretty fascinating, OS or not.
>
>> A hypervisor is a hardware
>> abstraction layer, messing about with the various memory rings in the
>> system in order to make the OS running within the hypervisor believe
>> it's running in Ring 0 when it's not in order to take advantage of
>> memory protection features in the hardware without tripping the native
>> hardware up when a child domain bombs out.
>
> Sure. And Linux is a hardware abstraction layer, making your application
> think it has a linear RAM address space to mess with and providing
> linear sequences of bytes on disk to read and write (organized as a
> single tree of names), when none of those are actually true. One of the
> jobs of an OS is necessarily abstracting the hardware in *some* way, if
> you accept that maintaining state and managing resources between
> independent applications is part of the definition of an OS.
>
> Of course you could argue either way. I was more contrasting Xen
> against a BIOS than arguing that Xen must necessarily be considered an
> OS.
True. I just wanted to make the point. ;-)
Jim
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On Mon, 05 Jan 2009 17:23:17 -0500, Jim Henderson wrote:
> INT2F redirection provided resources for redirection needed for network
> connections. And it included memory management routines
Just to clarify, "it" in the second sentence here means "MS-DOS" not
"INT2F", though I think some of the DOS extender functions probably were
accessed through 2F.
Jim
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nemesis <nam### [at] gmail com> wrote:
> Your definition is the Tanenbaum one, right?
I found this:
http://www.cs.rpi.edu/~hollingd/opsys/notes/Chapter1/Chapter1.pdf
I'm not exactly sure what it's supposed to be, but looks like some kind
of presentation about Tanenbaum's book.
Especially page 5 seems interesting.
--
- Warp
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Jim Henderson wrote:
> It's also probably a bit more involved than XEN is.
I'm not sure. I used it only vaguely. Note that the "VM" part means "virtual
machine", and "CMS" was the single-user OS that ran under it without change,
so I think the differences between that and XEN are probably pretty monor.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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On Mon, 05 Jan 2009 15:54:14 -0800, Darren New wrote:
> Jim Henderson wrote:
>> It's also probably a bit more involved than XEN is.
>
> I'm not sure. I used it only vaguely. Note that the "VM" part means
> "virtual machine", and "CMS" was the single-user OS that ran under it
> without change, so I think the differences between that and XEN are
> probably pretty monor.
Maybe, I'd have to talk to someone who knows VM/CMS better. Used to be a
guy I worked with who thought of VMware in those terms.
Jim
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Warp wrote:
> Especially page 5 seems interesting.
Considering it's named "modern operating systems", and I wouldn't exactly
count MS-DOS as a "modern operating system," I'm not surprised :-) The
contention of this paper (on page 5 at least) seems to be that no machine
running unsafe code without hardware protection can possibly be running an
operating system, nor can a machine like the Palm Pilot be running an OS,
since only one program runs at a time. I find this counter-intuitive, given
the existence of terms like "single-user operating system", "batch operating
system", and so on.
So, if the *compiler* enforces the protection (like Singularity or the
B5000) and not the hardware, does the code that regulates the sharing of
resources and runs threads outside the address space of any particular
applications count as an operating system? :-)
Page 22 seems to also contradict page 5, listing "handheld operating
systems" and "smart card operating systems", for example, neither of which
would seem to be allowing multiple programs to run at the same time, manage
or protect memory, or multiple resources in space.
I just think claiming that stuff like MS-DOS or WinCE isn't an operating
system, or that AppleDOS wasn't an OS, is going to confuse whoever one tries
to talk to. Again, it's like claiming C isn't a real programming language
because there are undefined programs that will compile and run.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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On Tue, 06 Jan 2009 01:07:31 +0100, Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
>> Especially page 5 seems interesting.
>
> Considering it's named "modern operating systems", and I wouldn't
> exactly count MS-DOS as a "modern operating system," I'm not surprised
> :-)
Note that in the actual book Tanenbaum explicitly calls MS-DOS an
"operating system" and in fact dedicates an entire chapter to it. "Modern"
in this context basically means the 1980s.
--
FE
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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > Especially page 5 seems interesting.
> Considering it's named "modern operating systems", and I wouldn't exactly
> count MS-DOS as a "modern operating system," I'm not surprised :-)
Would you call Unix a "modern operating system"? It was originally developed
in 1969, and as wikipedia puts it, "Unix was designed to be portable,
multi-tasking and multi-user in a time-sharing configuration."
But if you like, we could settle with: MS-DOS is not an operating system
by modern standards.
--
- Warp
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Warp wrote:
> Would you call Unix a "modern operating system"?
Only in the sense that there haven't been a whole lot of fundamental
improvements in OS concepts since then. At least, not that have caught on.
It's possible to be both old and modern: see plumbing, for example.
> But if you like, we could settle with: MS-DOS is not an operating system
> by modern standards.
I'm happy with "MS-DOS is a very limited OS that I wouldn't want to use for
general purpose computing these days." :-) I don't think we actually have to
settle into agreement here. The discussion was interesting, tho.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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