The TRS-80 booted to a basic prompt if there was no cartridge inserted. My dad got a book with a few hundred programs printed out, and one of use entered them in by hand and ran them. Then I would make changes to the code to make it do other things as well. I learn mostly by trial and error. When we got an Apple ][ clone I got a copy of "1001 things to do with your Apple II" and I was off to the races.
I finally took some formal classes in college, but spent most of my time lamenting the need to listen to things I had already learned.
The thing is, I had this opportunity because my parents had the resources to get the computers, and I was encouraged by teachers and friend to continue to learn. It is pretty clear that the best programmers all started by forth grade, not high school or college. If only rich white kids can start that early and boy are more likely then girls to take up computers as a hobby the current demographic deficiencies in the industry are likely to continue.