Dynamic Link Libraries

Hello,

I was searching the internet for information on using Dynamic Link Libraries and found your site very useful.  I have a few questions I am hoping you can help me out with.  Our companies main goal is to update our computer programs to a more user-friendly system.  What we have been doing is taking programs written in FORTRAN from our VAX system and converting them to Excel programs.  To date we have just used the equations from the FORTRAN programs and put them into Excel utilizing the Visual Basic editor to make nice Windows based user friendly programs.

In one of our Engineering meetings one individual suggested for some of the bigger programs that also contain proprietary data we should use Dynamic Link Libraries(DLL) to make the job easier and more secure.  The idea we discussed in the meeting was to use a DLL to run the old FORTRAN program in Excel.  Which from researching I don't think it can be done that way at all, correct?  Currently our FORTRAN programs are on the server and not each PC, so if you are traveling you can not use the programs.

In our current Excel programs we have used password protection to keep out unwanted changes or even viewing of the code in the Visual Basic editor.  I understand that these passwords with some malicious intent could be hacked into and perhaps the DLL would be safer because the program code would be on the server and not actually in the Excel Visual Basic editor.

From researching the topic I have some questions:
 
If we were to use the DLL concept, is it true the original FORTRAN code would have to be redone to remove all the user interface and have only the calculations in it and THEN a Visual Basic Code be written with the user interface that would call to our server to do the FORTRAN calculations?  If this is true, it would seem easier to do the program over in Excel's Visual Basic editor and put the proprietary data of the program in a DLL on the server but in Visual Basic format, yes?

Patrick McCormack
Mechanical Engineer
TRW Aeronautical Systems, Rome, NY
phone:  (315) 838-1281
fax:    (315) 838-1273 fax
email:  pat.mccormack@trw.com

McCormackPAsked:
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CrinCommented:
Hello Patrick,

Actually, there is no "Visual Basic" format as you called it in your last sentence, VB can easily exchange data with application written in any system (of course if these systems are designed to be used from the outside).

Generally, things you described are all possible. But there is a question - is it reasonable to do this or that way and at this point I cannot recommend you any solution due the project details lack.

What I recommend to do is: (1) do brief business analysis to determine requirements (what software should do, what security level required, other "what"s) (2) perform architect analysis - *how* to achieve requirements defined in (1) with minimal efforts and (3) perform actual development.

For more comments you are welcome to contact me at crin@mail.ru

Sincerely,
Crin
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rspahitzCommented:
Hello, Patrick.

We've actually done something similar to what you describe.  Our Fortran app work as DOS_Shell applications and return results in files that are manipulated by VB.

If you were to create the dll, would that be from the Fortran environment (which our Fortran compiler supports) or from a VB wrapper that encapsulates the fortran executable?

In our case, we left the code as a separate executable and have VB launch it and wait until it finishes the calculations before proceeding.

As for the user interface, you may need to get rid of it if it expects user input since the VB-to-DOS interface is weak.
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Richie_SimonettiIT OperationsCommented:
interesting...
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