This has certainly been an interesting learning experience.

In case anyone else attempts to do something like this, here are a few helpful comments:

Roger and I are developing several Earthquake Precursor computer programs.

A Perl program starts and watches the keyboard for key presses. When it sees one it sends that key press information to a TrueBasic program that starts running and processes the information.

When it is done, the TrueBasic program lets the Perl program know that it is finished. And the Perl program tells the Gnuplot plotting program to draw World Maps with some precursor data on them etc.

The latest thing that was learned is that each program should state on its Windows screen what it is doing at the time.

For example, the Perl program needs to tell program users when it is instructing the TrueBasic and Gnuplots programs to run, and what it is instructing them to do.

If the different programs do not do that then one might get trapped in an endless loop etc. and everything will stop. But no one will know which of the programs had the error causing everything to stop.

So, there appear to be some moderately complex conventions that programmers need to use so that they can effectively coordinate their programming efforts.