I can use them in the sense that I'm allowed to, but the compiler that I use can't compile FLIBS nor most of the libraries in your link; and the ones it could compile, I had to adapt, requiring understanding of what a 'hash table' is beyond just 'it's a key to value mapping'. I didn't want to make my post all about my Fortran problems, but I still think knowing the basics of fundamental data structures is foundational knowledge.