Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!telesoft!rlk
From: rlk@telesoft.com (Bob Kitzberger @sation)
Newsgroups: comp.realtime
Subject: Re: What is "real-time" really?
Message-ID: <722@telesoft.com>
Date: 3 Mar 90 03:15:30 GMT
References: <98692@linus.UUCP> <1556@mcrware.UUCP>
Organization: TeleSoft, San Diego, CA.
Lines: 31

In article <1556@mcrware.UUCP>, ylee@mcrware.UUCP (Yeongleh Lee) writes:
> 
>      So one characteristic of real time system is "Priority-based preemptive
> scheduling of tasks to ensure that the task of highest priority is executed
> when it becomes runnable".

A nit... these are characteristics of the tools used to implement a real-time
system, not the real-time system itself.

>      Another characteristics of real time system is "Direct control of the
> scheduler by user processes to guarantee the execution of the appropriate
> task".

For the Cyclic Executive model of real-time design, sure.  Other approaches such
as Rate Monotonic Scheduling are elegant solutions to deadline scheduling, but
mucking with the scheduler may invalidate RMS scheduling performed by your
runtime system or kernel.  So again, the need for this depends on the tool 
chosen to implement a real-time system.

Just trying to separate specification from implementation here...

	.Bob.

p.s. by the way, I agree with the poster that suggested someone put together a
     "what is a realtime system?" answer pack for monthly posting ;-)
-- 
Bob Kitzberger                  Internet : rlk@telesoft.com
TeleSoft                        uucp  :    ...!ucsd.ucsd.edu!telesoft!rlk
5959 Cornerstone Ct. West       at&t  :    (619) 457-2700 x163
San Diego, CA 92121-9891        "Dawn : The time when men of reason go to bed."
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