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From: info-mac@uw-beaver (info-mac)
Newsgroups: fa.info-mac
Subject: 
Message-ID: <1429@uw-beaver>
Date: Thu, 9-Aug-84 13:15:22 EDT
Article-I.D.: uw-beaver>.1429
Posted: Thu Aug  9 13:15:22 1984
Date-Received: Sat, 11-Aug-84 01:13:01 EDT
Sender: daemon@uw-beave
Organization: U of Washington Computer Science
Lines: 47

From: breuel@harvard.ARPA (Thomas M. Breuel)
Neither the MacIntosh operating system, nor the Mac user interface seem
to be oriented towards multi-tasking, meaning that it would probably
be very hard, or impossible, to get two independent, unco-operative
to run at the same time. On a high level:

-- how would you handle the different menu bars for different applications
   running at the same time?
-- how would you give the user a chance to switch between tasks? 
   You can't just put them into the Apple menu, because that is managed by
   the application itself, and usually created via _AddResMenu. Maybe
   add a desk accessory to do it? What about applications that don't
   support desk accessories?
-- how would you handle windows? Leave behind windows belonging to different
   tasks? What happens if the user clicks in a window belonging to a
   background task? Bring it into the foreground? 

On a low level:

-- look what a hack desk accesories are: they have to be 'drivers'
   to co-exist with an application.
-- is the ROM re-entrant? I don't believe so... how would you handle 
   the current grafPort? and all the other global states of the system? 
   save them all?
-- there is no memory management unit on the Mac. There is no protection
   among tasks.
-- what about (asynchronous) i/o? What about background tasks doing
   i/o on windows? Usually the window on which i/o is done is the foremost
   (active) window. Could one just ignore this convention?
-- many more questions...

Sorry for the poor organisation of this collection, but I think, altogether,
it is likely that the MacIntosh is not going to have a multitasking
operating system for quite a while, and not without major changes to
the ROM and the user interface. If you want to get multitasking and
windows, get a LISA 2/5 with the office system, or, better, get a good
SmallTalk implementation (if you can afford the hardware).

This is not to say that you'll not be able to get some kind of
multitasking -- you can write desk accessories that do things
semi-concurrently, or certain interpreted and compiled programming
languages may support multitasking, like Basic or Modula2. I believe
that running theWord in one window and Sargon in the other will not be
possible for quite a while.

					Thomas.