How to interact with fortran code

[seany via Digitalmars-d-learn]

I apologize many times for this question, may be this had already 
been answered somewhere, but considering today the last of my 
nerve is broken, I can not really find the soution.

So I have a D code, which acts as a central manager of all my 
codes, reads user input, reads files, etc, and based on the file 
readouts, I would like to pass some variables from the D code to 
a fortran code, in binary format, perhaps, if such a thing 
exists, instead of encoding to text/ ASCII first.

I would also like to read some (not all) variables back from the 
fortran code.

The Fortran code resides in a subdirectory to the path/to/d/code

How to do this? is there a preffered way / easier than system 
call way to interface D and Fortran code? This must be Fortan 
code - these are the standard atmospheric chemistry codes.

I apologize again if the question is stupid, trust me, today all 
my nerves are broken.