Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!unmvax!polyslo!dorourke
From: dorourke@polyslo.CalPoly.EDU (David M. O'Rourke)
Newsgroups: comp.sys.amiga
Subject: Multi-tasking and OS books
Message-ID: <11336@polyslo.CalPoly.EDU>
Date: 12 May 89 19:44:45 GMT
References: <17148@usc.edu> <24279@agate.BERKELEY.EDU> <18268@cup.portal.com> <17183@usc.edu>
Reply-To: dorourke@polyslo.CalPoly.EDU (David M. O'Rourke)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 32

In article <17183@usc.edu> papa@pollux.usc.edu (Marco Papa) writes:
>rely on MultiFinder.  Apple can try to fool end-users into thinking that 
>MultiFinder provides multitasking, but I don't think anybody on Usenet
>will ever believe that.  If you do, may I suggest you pick up ANY Operating
>Systems book.  It might be very educational.

  Although pre-emptive multi-tasking is desirerable, no OS book I've ever 
seen *requires* it.  So multi-finder is multi-tasking.  It allows more
than one process to be resident, and they will execute. You can have
programs doing serveral things "at once", right now I have a clock program
smartcom, and a rotating globe all executing under this non-multitasking
OS.  In face I believe OS/2 isn't pre-emptive either, it does task switches
on OS calls {I might be wrong}.  I do know that the Unisys A-Series low
end machines have a "true" multi-tasking OS and they aren't pre-emptive, they
do a context switch on OS calls {MCP if you work for Unisys} and a context
switch on I/O blocking.

  Multi-tasking is the ability to have more than one process resident, and
the ability to schedual more than one process to have access to the CPU.
All the OS books I've ever seen only require some form of task schedualing,
the most popular {and probably best} scheme is with an external clock that
triggers a CPU context switch to a task manager, that then decides who gets
the next time slice of CPU.  Failing to have an eternal clock, you then have
to perform the task switch at some other time.  I believe hooking this
task switch in with one or more OS calls is an undesierable, but workable
way of doing things.  Your right multi-finder isn't pre-emptive, but it
is multi-tasking.
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David M. O'Rourke____________________|_____________dorourke@polyslo.calpoly.edu
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