Using FORTRAN in your DLL

It is possible to wrap compiled FORTRAN code in C or C++, allowing Mathcad to run it. In this way, legacy FORTRAN code can be reused as a Mathcad function. We have had success compiling with Compaq Visual Fortran (formerly MS Fortran) and MS Visual C++ 6 or 7.

First, follow the directions for Compiling and Linking your DLL to set up the Visual Studio environment with all the appropriate settings for creating a UserDLL. Next, create a static library from the FORTRAN subroutine. Link the C code to the FORTRAN code, and compile a DLL in the usual manner for Mathcad use.

Create the Fortran Library

Create a new "FORTRAN Static Library" project in Compaq Visual Fortran 6.6B, and add your files to the project.
Under the Build menu, select "Set Active Configuration" and choose "Release."
Compile and build. The Release subfolder of your FORTRAN project now contains [myfortranlib].lib.

Modify the C code for the UserDLL

Once you have the FORTRAN library, you need to add in your C code:

extern void __stdcall FORTRANFUNCTION(const double *array1, const double *scalar1 [, etc.]); // Since FORTRAN typically expects arguments by reference, arguments are passed // as pointers. To pass values, the FORTRAN code must contain a compiler directive // telling the function to expect a value rather than an address. LRESULT mcadfunction(LPCOMPLEXARRAY array1, LPCCOMPLEXSCALAR scalar1, etc.) // this defines the function before FUNCTIONINFO, using the same variable names // called by the external FORTRAN function. {

// some error checking goes here,
		 followed by the

		 // actual call to the FORTRAN function. For example, 

		 FORTRANFUNCTION(&array1->hReal[0][0],
		 &scalar1->real [, etc.]);

		

		// Either the function call must be in UPPERCASE, or you will have
		 to set

		 // Settings->FORTRAN->External procedures->External name implementation

		 // to "Upper case" in your FORTRAN compiler. Any other C functionality
		 follows...

		return 0;

Link the Library

In an existing C project in MS Visual C++ or Visual Studio, select the Link tab and then Input from the Category dropdown menu. Enter "[myfortranlib].lib" in the "Object/library modules" textbox at the end of the list.
Enter "libc.lib" in the Ignore libraries text box.
Enter the path of the [myfortranlib].lib file in the Additional Library Path text box, for example, "C:\temp."
Compile and build the DLL.

Notes:

FORTRAN code should be run as a separate thread, rather than directly as a function. This way, if the process is terminated - for example, by a user pressing [Esc] - the whole thread can be killed without checking which FORTRAN subroutine is currently active.
It is useful to replace all "STOP" statements in FORTRAN code with a special function returning an error code to the calling C which will terminate the thread gracefully.
If the FORTRAN code contains "PRINT" to console statements, these can be converted by reassigning console to a file, so output goes to a file instead of the screen. If the FORTRAN routine terminates with an error, the C++ front-end can be programmed to read this "log" file and display it as a window. For example:
SUBROUTINE INIT_STDOUT () c this subro which redirects FORTRAN output to file use dfwin integer res c CALL close_stdout res=SETENVQQ("FOR_PRINT=C:\FORT_OUT.TXT") c PRINT *, 'Print a character to initialize ' PRINT *,' ' RETURN END
If you wish to distribute a FORTRAN-based DLL, the computer which runs it will need to have the appropriate FORTRAN runtime libraries installed. These can be any of the following: DFORRT.DLL, DFORRTD.DLL, DFORMD.DLL, DFORMDD.DLL, DFDLG100.DLL, or MSVCRT.DLL. If these DLLs are missing, "file not found" errors will result. These DLLs are freely distributable, and should come with your FORTRAN compiler. They must be installed in the Windows/system32/ or WINNT/system32/ directory.