How You Tell the Machinery What To Do
I still like BASIC for its simplicity. I still turn to C when I'm doing "serious" work. But it really doesn't matter; choose your language based on what you think will be the best fit for you. Maybe that means it's cheap or free. Maybe you know someone who's an expert and can help you during the painful early phase. Maybe the awesome robot arm that you just got at the scrap yard has a controller that needs a FORTRAN program to run it...
Fortunately, with the wealth of information, tutorials, and software libraries available on the net, learning a language has only gotten easier. There are many sites that can explain more about programming than I can, but I offer a few tips for the beginner: