In the spirit of "how could I not have known that:" back in college there was a terminal in a room in the physics department basement where I could log in and check my email. Nearby was a bookshelf with a bunch of tattered books that seemed to have been left by former students. Some Asimov, some Douglas Adams, books about Fortran and C, and a book about Unix. Absent-mindedly flipping through those books one day (as one did before one discovered the web) I noticed that the Unix command line prompt looked like what I saw when I logged in to read my mail. Huh. I tried some things from the book, and they worked just like Unix was supposed to. This thing I had been using to check my email all year could do other stuff! That was really cool, but not all that personally useful to me, until I read something in the book that made me realize there was probably a C compiler. There was! Even better, there was a C++ compiler. From then on I was hooked. Programming for me had been a hobby before I came to college, a way of avoiding real work. I had heard of C++ and wanted to learn it, but I had read that the compilers were really expensive, and I was afraid of asking my parents to buy me one. Here was one I could use for free! So naturally I ended up spending a lot of hours writing C++ code in that basement instead of doing my math and physics work, and that's how I acquired the skills that landed me my first job.

As for Linux, there was a CS major in my dorm who installed Linux and BeOS on his PC and did his programming assignments on them, but I never had the courage to do that, because I was afraid that if I screwed up my computer and couldn't immediately fix it, it would mess up my work for other classes. I didn't take that risk until years later, when I no longer had to turn in writing assignments in Microsoft Word format.