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Mail Archives: djgpp/1994/07/18/16:17:39

Date: Mon, 18 Jul 1994 15:24:27 -0400 (EDT)
From: David Max <max AT SLINKY DOT CS DOT NYU DOT EDU>
Subject: Re: Real-time OS under DJGPP
To: DJGPP <djgpp AT sun DOT soe DOT clarkson DOT edu>

On Mon, 18 Jul 1994, Martin Haltmayer wrote:

> What do you mean by 'real-time multitasking'? I always supposed
> real-time to be the contrary to multitasking... either a process owns the
> cpu (real-time) or shares it (multitasking)???
> Martin haltmayer AT uni-augsburg DOT de
> 

Multitasking is running two things at the same time. Real-time just means
that somewhere somehow there is a reference to time and/or meeting
deadlines. Perhaps there is a user who is waiting for a response or a
serial port interrupt that needs immediate attention. So far all there is
available for DJGPP is multitasking based on the idea that every task runs
until it decides to relenquish control. This leaves it up to the
programmer to make sure that all tasks release control in a timely
fashion. I suppose what is meant here by "real-time" is that the task 
scheduler should at the very least be preemptive so that the programmer 
doesn't have to worry about writing programs that run for too long 
without releasing control.

David Max
New York University




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