I learned to code on a TRS-80 Model 100, in BASIC, when I was 7 years old or so. Nothing Unix-like about it, but as an introduction to programming concepts I got a lot of mileage out of it. The upside is, there are no distractions, and it basically doesn't do anything except let you write text or short BASIC programs. It's essentially a big keyboard with a little chunky LCD display and it runs a long time on AA batteries. I dragged it everywhere with me as a kid, along with the BASIC manual, trying to figure out how to get it to do things. The portability was a big plus, cause I could just keep experimenting whenever I had ideas.