Xref: utzoo comp.realtime:264 comp.software-eng:2192
Path: utzoo!attcan!utgpu!watmath!iuvax!rutgers!sunybcs!planck!news
From: westley@avenger.uucp (Terry J. Westley)
Newsgroups: comp.realtime,comp.software-eng
Subject: What makes a system "real-time?" (Was: Real-Time references wanted)
Summary: If the answer to a problem is late, it is wrong.
Message-ID: <1989Oct18.151758.5227@planck.uucp>
Date: 18 Oct 89 15:17:58 GMT
Sender: news@planck.uucp (Usenet News)
Reply-To: westley@avenger.UUCP (Terry J. Westley)
Followup-To: comp.realtime
Organization: Calspan Corporation ATC  Buffalo, NY
Lines: 19

In article <2925@zaphod.axion.bt.co.uk> rdoyle@zaphod.axion.bt.co.uk writes:
>I am currently involved in some work on real-time  [..]
>	1. What characteristics of a system make it "real-time"?

Here's the definition I use for what makes a system "real-time:"

	A system is real-time when the result of some
	operation is wrong because it is late.

In particular, time is not absolute.  It may be microseconds or days,
depending on the application.  Some people use the term "hard real-time"
to distinguish between systems.  What they really mean is that their
system is more real-time than yours, and that it is harder to design and
implement.  That's usually true, but not necessarily.

Terry J. Westley
Arvin/Calspan Advanced Technology Center
P.O. Box 400, Buffalo, NY 14225
planck!hercules!westley@cs.buffalo.edu