real-time system - a word processor


Clarification on "real-time system":

A word processing system, if it is very slow to respond, say it takes

15mis or longer after typing each key for it to print to the document, would you consider it to be a "real-time system" ?


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Tauno Voipio
tauno voipio (at) iki fi
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Tauno Voipio
2005 skrev:

What do you mean by "15mis"? 15 minutes?

As for "real time" or not, the system is "real time" if all operations are completed "sufficiently fast". The hard part is, of course, to determine exactly what "sufficiently fast" means...


Reply to
Rune Allnor

An excellent answer!

We all picked up on it quickly that 2005's questions gives away his age and experience. His perspective is limited by experience (or lack of it) and so the language he uses and his expecations from it are similarly limited. We were all inexperienced like 2005 is at one point in our lives.

I'm not lecturing but just noting that language will bite you in the ass every time you fail to use it accurately. 2005 needs to understand that every word he writes is significant and weighty. It's my pet peeve with my colleagues who say one thing and mean another. That's why I'm writing this.


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I would say that a real time system is one where there are _requirements_ that things have to be completed within certain time limits. Even if they aren't completed sufficiently fast it's still a real-time system, it's just one that's broken.

Grant Edwards                   grante             Yow!  A dwarf is passing
                                  at               out somewhere in Detroit!
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Grant Edwards skrev:

If you say so...

The answer was inspired by a request to contribute to a marine operations project a few years ago. The customer was about to deploy this piece of equipment at the sea floor, with very tight bounds on positions. Consequently, they needed to monitor the positions of the gear as it was deployed, keeping track of position beakons as they were lowered down the water column.

In our brief the objective was to keep the beacon positions updated in "real time". A general procedure was outlined where all sorts of bells and whistles were included; orthogonal codes, signalling robust with respect to Doppler, you name it (I can't help thinking the spec was a cut'n paste of the GPS position system with some more constraints added...).

As I looked into this, I never really figured out why "Doppler resistance" would be necessary. The laying vessel would travel at 1 knot at most, inducing insignificant Doppler. As for orthogonal code requirements, the deployment velocity would never exceed 2 m/s, meaning that the position could be triangulated to within 5 m in five seconds or so, by coordinating reference beacons. Even if such coordination should not be possible, using different frequency bands for different beacons ought to be possible. Real time? Marine operations work on a time scale a few orders slower than most other operations. One position update every minute would be plenty; one would not be able to react faster, and it would take at least five minutes from corrective actions were initiated onboard the vessel to effects would be observable in the path of the gear to be installed.

Maybe not surprising, then, that the project was cancelled...

Heh, don't get me started along those sorts of lines... ;)


Reply to
Rune Allnor

I used to know someone who supposedly (I never actually saw it) could type faster than the PDP-10 interrupt routine could process characters from the input port. In that case, it would not be a real time system.

-- glen

Reply to
glen herrmannsfeldt

I think you could still call it a real time system, it is just the operator that typed beyond specification.



Reply to
Josep Duran

I remember an example of a real-time system where times specified in days; the payroll. The data has to be at the bank at a certain date, or everybody gets their salary too late. (and will be very upset)


Reply to
Wim Ton

Well, every keyboard I have had since they became serial is not real time by that criterion, come to think of it. Try it yourself: just type "move" fast enough and it gets "mvoe".... (those I refer to are Cherry keyboards, perhaps other manufacturers have different controllers and use different scanning sequences where this might not apply). I know it is the keyboard because I have written the interface to it - a number of times, actually. Well, I seldomly type that fast ... but because I type a lot of "move"s, this has been with me over the years, notifies me when I need a break :-).


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glen herrmannsfeldt wrote:

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Crikey! It does get mvoe!

Still, is it my unsynchronised hands, the left rushing to press the key before the right hand has finished typing, or is it really the shonky scanning?

Reply to
Judges 13:18

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