James Newton, Host wrote:

>> I'm not sure what exactly the problem is you're trying to solve with the
>> conversion to an applet. Running a Java app can be as simple as
>> downloading the jar file and double-clicking on it, and you're done
>> with it. 
> 
> The issue is one of presentation. I don't want to type volumes of
> explanatory text into the circuit design as text labels. And I would
> like each of the samples to accompany the text in the web page. "As you
> can see in the applet window below, the counter is formed from three JK
> flip flops and their binary output is decoded to sequential (decimal)
> wires to enable each of the different operations required in the
> processor in the proper order."

In that case, it seems you don't want the applet to necessarily allow
loading and saving arbitrary files. Loading files from the server would be
enough, and saving is not necessary. You could just take the source, follow
the few simple steps in that link I sent and see whether it works.
Depending on the app it just might... (The app supporting loading a
simulation file through the command line helps.) 


Alternatively...

> In addition to the text, I want to include pictures of the real chips that
> are being used in the circuit, links to sources and other web sites, and to
> the next lesson or sample circuit.
> 
> I could take the hours required to produce GIF animations of the circuits
> operating, but that would remove any user interaction. "press the button
> labeled "Clock" to see the counter advance to the next value." 

You could make the page, with the text and pictures you would put there,
but instead of the applet there is a link to the simulation file that the
user is supposed to load in the app. After loading that file into the app,
they have basically the same thing: they see what you're talking about
live, but instead of it being in the same window, it is in a different
window. Which, from a user POV, may be an advantage. It is easier to
Alt-Tab back and forth between the app and the browser than it is to scroll
up and down all the time between the text and the applet.

Just as assurance for the doubtful that they have done the right thing and
loaded the correct simulation file you can include a simple screen shot,
without any interactivity. Serves also as teaser ("oh, looks cool, let me
try this"), and is not really much work (compared to setting all the rest
up).

> And it would be interesting to allow the user to modify or set up circuits
> along the way. "What would happen if the circuit were changed to connect the
> inverted clock signal to the first stage and the non-inverted clock to the
> second stage? Try it and see: Just click on the wire from the clock to the
> first stage and the inverter to the second stage and delete them. Then draw
> new wires connecting the clock to the second stage and the inverter to the
> first stage. Start the simulation and try the new circuit. Do you see the
> difference?"

Would still work, and much easier as the app doesn't have the headaches of
the applet when saving files locally.

> A student coming to the web page could instantly start learning about logic
> circuits and see them operating, interact with them and change them with
> guidance from the web site.

It would be a little bit less instant ("You need to download this .jar file
and double-click on it to run the application. Then you load this circuit
file"), but I think the difference is not that big. 

In any case, it's something that could get this started even if the applet
thing doesn't work. And it is structured the exact same way, so if at some
point you decide to replace the screen shots with applets, not much else
changes.

Gerhard

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