Path: utzoo!attcan!uunet!mcsun!hp4nl!star.cs.vu.nl!ast
From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Re: dosread.c again
Message-ID: <3768@ast.cs.vu.nl>
Date: 22 Oct 89 15:50:15 GMT
References: <695.254152F7@mudos.ann-arbor.mi.us>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 70

In article <695.254152F7@mudos.ann-arbor.mi.us> mju@mudos.ann-arbor.mi.us (Marc Unangst) writes:
>I'm not Andrew Chan, but I can tell you the things MINIX lacks 
[Summarized]

 1. Large model.  A real ugly hack forced by the brain damaged Intel
    architecture.  MINIX doesn't inherently have an 64K limit.  On the
    Atari you can have programs as large as physical memory.  I expect
    the arrival of the 386SX will spell the end of the 8088 and 80286
    within a couple of years.  At that point we can adopt a single linear
    32-bit address space, like MINIX-ST.

 2. Virtual memory.  I tend to regard this as obsolete.  With Bruce Evans'
    protected mode kernel and a 2M 386 you can have up to 2M of programs
    running at once.  That has to be enough for a personal computer.
    Thus I see virtual memory as something with a lifespan limited to
    the older machines, which will probably be gone in a couple of years.

 3. A real shell.  The shell is pretty much the Bourne shell.  If it has
    bugs, please try to fix them.  No conceptual problem there.  You may
    have an old version.  I have extracted some pretty large shell files.
    Make sure you have enough stack (chmem).

 4. UUCP.  I believe Peter Housel posted something along this line (uupc).

 5. Mail.  There actually is a mail program, but it is only for local
    mail at the moment.  I'll (re)post it as part of 1.4b.

 6. Root on hard disk.  That is already in as of 1.4a and will stay in.

 7. Boot off hard disk. I suppose it is possible, but a low priority item.
    Many people still use DOS and want to have the hard disk boot start DOS.
    You can't have it both ways.

 8. Job control.  No way. Too messy.  Maybe virtual screens next time.

 9. A format program.  I'd love it.  Any volunteers?

10. Backup.  There is no dump/restore, but I wrote a program called backup.c
    and posted it.  I use it all the time and find it quite adequate.
    You give it the name of a directory and put a floppy in the drive, and
    it looks for files that have changed since the last backup and saves them
    all.  I even have a shell script that calls the program with the right
    flags (which I posted).

Conclusion
>> With the addition of these changes (or at least most
>> of them), I might consider eliminating DOS entirely from my machine.

I find this a bit odd.  As far as I can see, the scorecard is:

  Item				DOS	MINIX
 1. Large model			Yes	No
 2. Virtual memory		No	No
 3. Real shell			No	Almost
 4. UUCP			No	UUPC
 5. Mail			No	No (except local mail)
 6. Root on HD			Yes	Yes
 7. Boot off HD			Yes	No
 8. Job control			No	No
 9. Formatter			Yes	No
10. Dump/restore		No	No (although I think 'backup' is better)

If one is willing to concede that the Bourne shell is close enough, and
accept UUPC, it looks like the score is 4 to 4.    I can easily understand
someone saying "Until MINIX gets virtual memory I'll stick with XENIX,"
but the list above (except for large model, doesn't really put DOS in that
great a light either). And things like multiuser, multiprogramming,
ability to use 16M memory, etc. aren't really strong points for DOS either.

Andy Tanenbaum (ast@cs.vu.nl)