Some interesting mixed Fortran-C projects

I’ll provide a list here of some of what I think are interesting and useful mixed Fortran-C projects. I encourage you to play with them, explore the source code, and see other possible ways to interface with C code from Fortran:

• DISLIN, a fully featured graphics and data visualization library, with its own interpreter included, and bindings to Fortran and several other languages: https://www.mps.mpg.de/dislin
• Earth System Modeling Framework (ESMF), a mixed Fortran-C++ library for building and coupling parallel Earth system models: https://www.earthsystemcog.org/projects/esmf
• F03GL, a Fortran interface to OpenGL: http://www-stone.ch.cam.ac.uk/pub/ f03gl/index.xhtml
• fgsl, a Fortran interface to the GNU Scientific Library: https://github.com/ reinh-bader/fgsl
• gtk-fortran, a Fortran interface to GTK for building graphical user interfaces: https://github.com/vmagnin/gtk-fortran/wiki
• NetCDF, for reading and writing self-described, compressed, gridded, multidimensional datasets: https://github.com/Unidata/netcdf-c (C library) and https://github.com/Unidata/netcdf-fortran (its Fortran bindings)
• PLplot, yet another fully featured graphics and data visualization library with bindings to Fortran and many other languages: http://plplot.sourceforge.net
• OpenBLAS, one of the fastest open source linear algebra libraries in the world: https://github.com/xianyi/OpenBLAS

Now that you’ve gotten this far, what are you going to make?