Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!mips!bridge2!jarthur!polyslo!jdudeck
From: jdudeck@polyslo.CalPoly.EDU (John R. Dudeck)
Newsgroups: comp.os.minix
Subject: Re: A real operating system ?
Keywords: future 1.5
Message-ID: <25eda193.62e3@polyslo.CalPoly.EDU>
Date: 1 Mar 90 22:26:27 GMT
References: <1383@Terra.cc.brunel.ac.uk>
Reply-To: jdudeck@polyslo.CalPoly.EDU (John R. Dudeck)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 45


In article <1383@Terra.cc.brunel.ac.uk> eesrajm@cc.brunel.ac.uk (Andrew J Michael) writes:
>Several people have recently commented that MINIX is a teaching operating
>system, not a real one.
>
>So what makes a real O/S ?  Is it the O/S itself, or the utilities which
>come with it ? 
 
I would say that what makes a real OS is the OS itself, not the utilities.
After all, it is possible to set up an entire set of the Unix utilities
under MS-DOS, and give a very Unix-like feel to DOS.  Of course what is
missing when you do this are the multiple processes of Unix.

An OS's purpose is to provide a high-level interface to the underlying
hardware, at the system-call level.  A "standard" operating system provides
a standard interface, so that there is portability of software between
systems.  A "real" OS is one which provides a reasonably complete mapping
of the capabilities of the underlying hardware into a higher-level programming
interface.  In addition, there are a number of other non-hardware related
services provided by a real OS, such as multiple processes.

>Surely no-one in their right minds would buy MSDOS as an
>operating system; they buy it for the programs they can run on it. 
 
This is true.  MS-DOS lacks many of the elements that are generally considered
to be part of a "reasonably complete" OS, such as multiple processes, access
to a reasonable amount of memory to run programs in, etc.  On the other
hand, it does provide better support than Minix for some parts of the
hardware, such as the range of floppy and hard disks available, and the range
of video adapters.

In my opinion, Minix is close to being a "real" OS.  Here is what I think
it still lacks:
   - Support for full use of available memory by programs.  In the 80x86 world
     this means support for the large memory model.
   - Support for the math chip in context switches (has this been added?)
   - Support for the full range of hard and floppy disk types available
     on whatever platform it is running on.
   - Swapping (has this been added?).
   - Spooled printing.

Of course there are a lot of other things that would be nice.
But these are the main things that Minix lacks, which keep it from being
viable as an OS used in say, a business setting.  Without these, the range
of applications is limited, and the frustration level is too high.

-- 
John Dudeck                           "You want to read the code closely..." 
jdudeck@Polyslo.CalPoly.Edu             -- C. Staley, in OS course, teaching 
ESL: 62013975 Tel: 805-545-9549          Tanenbaum's MINIX operating system.