I spent 35+ years in industry programming Windows programs for simulation, estimation and optimization of mineral processing operations.
I have a Ph.D. in Metallurgical Engineering and upon obtaining that I spent 10 years programming real-time estimation programs for mineral processing as well programming estimation algorthims for estimation of model parameters from lab and plant testwork. I programmed them first in Fortran and then in C++. Then I spent another 15 years programming dynamic simulators for mineral processing plants. They could be used for sizing equipment given the failure rates of equipment and the time to repair them.
Now I have learned a different type of programming, that of full stack flex developer and will be looking to find freelance work.