Xref: utzoo comp.realtime:272 comp.software-eng:2222
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From: rlk@telesoft.com (Bob Kitzberger @sation)
Newsgroups: comp.realtime,comp.software-eng
Subject: Re: Real-Time references wanted
Summary: Favorite quotation, Anecdote
Message-ID: <568@telesoft.com>
Date: 20 Oct 89 02:33:11 GMT
References: <2925@zaphod.axion.bt.co.uk>
Organization: TeleSoft, San Diego, CA.
Lines: 45


In article Richard Doyle writes:
> 
> 	1. What characteristics of a system make it "real-time"?
> 

I'll throw in an anecdotal description of real-time systems...

Here's my favorite quotation on the subject, which appears in DeMarco's
foreword to _Strategies For Real-Time System Specification_ by Hatley &
Pirbhai :

	"Most systems people use the term ``real-time'' rather loosely,"
	the young manager said.  [...] "They say they've got a real-time
	constraint when they're worried about impatient insurance brokers
	or bankers sitting in front of their terminals.  A real-time
	system, in their minds, is just one that needs to be `quick as a
	bunny'.  If they fail to meet that constraint, their users might
	be inconvenienced or even annoyed.  When we use the term, it means
	something rather different."

	Her coworkers began to smile, knowing what was coming.  "We
	build systems that reside in a small telemetry computer,
	equipped with all kinds of sensors to measure electromagnetic
	fields and changes in temperature, sound, and physical
	disturbance.  We analyze these signals and transmit the results
	back to a remote computer over a wide-band channel.  Our
	computer is at one end of a one-meter long bar and at the other
	end is a nuclear device.  We drop them together down a big hole
	in the ground and when the device detonates, our computer
	collects data on the leading edge of the blast.  The first
	two-and-a-quarter milliseconds after detonation are the most
	interesting.  Of course, long before millisecond three, things
	have gone down hill badly for our little computer.  We think of
	*that* as a real-time constraint."

.Bob.
-- 
Bob Kitzberger                  Internet : telesoft!rlk@ucsd    
TeleSoft                        uucp :     ...!ucsd.ucsd.edu!telesoft!rlk
5959 Cornerstone Ct. West       at&t :     (619) 457-2700 x163
San Diego, CA 92121-9891        
   "It's a damn poor mind that can only think of one way to spell a word."      
                                           -- Andrew Jackson
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