My programming experience was unexpressed before college as I was mostly interested in basic sciences - mainly physics. It was only after high school did I seriously get into CS type of stuff as I started developing an intesrest in AI/algorithms. So for me, it is not hard to believe that there could be a lot of people with a hidden aptitude for programming. After all, programming is a means to an end. After high school, understanding the brain and developing AI was my "end", which obviously requires strong programming skills and thus subsequently triggered a stronger interest for programming.
I started programming late into highschool as well, and only a TI83 at that. My first rendezvous with network/gui programming started in college (though I was a CS major).
Now, more than half a decade after graduation and working in silicon valley, I'm hacking on more serious projects like writing operating systems. I don't think starting late has affected me negatively too much. Just keep at it, you'll reach your full potential before you know it.
