How to compile f77 and f90 files together with gfortran

Question

I have a few dozens files with f77-functions and I would like to include them into my f90-program. How do I bring it altogether with gfortran? If I just try to

gfortran myprogram.f90

it complains for f77-code in the other files. As I understand, it would like to see all files put into definite standard (f77 of f90).

Answer 1

Your problems aren't F77 vs F90, they are fixed-form vs free-form. You cannot combine both source formats into a single file. You have two options:

1. Modify all of your source into one format (use free-form if you are going to do this), then compile your program as you are doing now.

2. Put all the fixed-form stuff in one bunch of source files and all the free-form stuff in another bunch, then do:

   gfortran -omyprogram free-form-stuff.f90 fixed-form-stuff.f
   

   This will compile each source file separately and then link them together into one executable.