Recently discovered this site <https://hpc-wiki.info/hpc/HPC_Wiki>, which gives some useful introductory info to those wanting to learn how to program a supercomputer (or just curious about the process). For example, here <https://hpc-wiki.info/hpc/MPI> is an intro to one parallelization architecture, called MPI, and here <https://hpc-wiki.info/hpc/OpenMP> is an intro to another one, called OpenMP. Note the examples are given in C and Fortran, and both rely heavily on preprocessors/compiler plugins in order to generate the right code. Yes, Fortran is still in heavy use, it seems. And if you learned your Fortran before the 1990s (as I did), you may not even recognize it as the same language.