Path: utzoo!attcan!uunet!munnari.oz.au!ditmela!yarra!bohra!als
From: als@bohra.cpg.oz (Anthony Shipman)
Newsgroups: comp.os.misc
Subject: Re: Macintosh OS (was: 68000 and Workstations.)
Summary: defining an OS
Message-ID: <109@bohra.cpg.oz>
Date: 29 May 90 09:13:42 GMT
References: <30273@ut-emx.UUCP> <76700207@p.cs.uiuc.edu> <6392@scolex.sco.COM>
Organization: Computer Power Group, Melb, Australia
Lines: 33

In article <6392@scolex.sco.COM>, seanf@sco.COM (Sean Fagan) writes:
> Most people consider that a *true* OS has protection of some sort; that is,
> some way of making sure that programs don't step on each other and can live
> in peace and harmony. (Sometimes, this is done just to make sure that the
> program doesn't step on the OS, true, but it's still nice to be there 8-).)
> 
> Ask yourself this: using your "OS," following all of the rules, is it
> possible to write a program that will lock up the machine?  On the Mac, I
					^^^^ bugs notwithstanding??

> No, the next trick would be to make sure that people take an OS course
> before defining what an OS is.  That's going to be very, very hard, though,
> I think.

What sort of OS? A "time-sharing" OS is supposed to create the illusion of one 
virtual machine as the programmer's model. Therefore memory protection, 
relocation, multi-tasking etc will be required. I can generate subgoals for
defining:
	1  single user (multi-tasking)
	2  multi-user (multi-tasking)
	3  time-sharing
You could define OS to cover any or all of the above. The Mac is certainly not
3 nor 2. It could be 1 depending on how you define OS.

I suspect that what passed for an OS in the machines of the 50s was a set of
I/O etc. routines which loaded programs and called them as subroutines, like 
the Mac. I would vote the Mac's system software as an OS, albeit 
primitive in style.
-- 
Anthony Shipman                               ACSnet: als@bohra.cpg.oz.au
Computer Power Group
9th Flr, 616 St. Kilda Rd.,
St. Kilda, Melbourne, Australia
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