Under Windows, I would look at Visual Studio Community. I believe it supports Fortran. Under Linux, try GFortran.

By "ancient", do you mean Fortran II or Fortran IV? Fortran has evolved a great deal since those days. I would wonder if "ancient" will compile any more, as originally written.

Depends a bit on what you mean by ancient, and what the original code was written to run on. Every manufacturer had their own “standard Fortran subset” compiler but tended to add specialized features for speed or efficiency.

Gnu Fortran should do the job (documentation at https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gfortran/ ) for most programs written after about 1980. It has lots of switches to cover different variations of int and real sizes in bytes, function handling, etc.

If it is a program from a 24 bit IBM machine there may be some fix up required to your code. Or you could run an MVS emulator like Hercules with an IBM native compiler :)

cheers

gfortran will be helpful.

I tried to install Visual Studio Community and found that it is easy to do so, however running Fortran requires several steps. Could you kindly tell me what's wrong with me?

It’s the computer’s fault, nothing wrong with you ;!) But seriously, if you are using Windows and VS, it looks like only the Intel oneAPI Fortran compiler will work easily. These links may help clarify:

https://fortran-lang.org/en/learn/os_setup/

https://www.intel.com/content/www/us/en/developer/tools/oneapi/toolkits.html#hpc-kit

you need the Intel oneAPI base and HPC toolkits.

A slightly dated setup is found here: https://people.sissa.it/~aboiardi/post/fortran-on-windows/

Good luck. Windows is probably not the easiest environment in which to do Fortran programming.

Now, that having been said, if you have and can use Linux it could be a better environment for working with older Fortran code. There is a world class set of development tools and widely used practices for Fortran development on Linux. Again, these folks have a good intro to compiling and linking programs on Linux: https://fortran-lang.org/en/learn/building_programs/compiling_source/

Cheers

I used the original Fortran before there were numbers. (Fortran II was in beta :). I confirm there are implementation/platform variations. Since the program is F77 or F90 according to Fardousi Ara Begum , at least there might be free-form input and not the fixed 72-column lines where the first 6 positions have special purpose. :) :). I also suspect that the Intel Fortran might be the best choice on PCs. And yes, there's a Fortran in GCC. That could be tried also.

I don't know about "easy to use" for any of them. I assume command-line (i.e., "terminal") operation and an understanding of the usual compile, link, execute staging is required.