My grandpa bought me a TRS-80 when I was 4-5 (don't recall exactly) because "computers are the future." My only cartridges were LOGO and Sokoban so if I wasn't in the mood to push boxes around...

I don't know if you can really call it programming but I'd spend hours writing out huge I/O conversations with the computer that only worked if you knew how it was supposed to go in advance. I found it fascinating.

"Hello, I'm a computer, what's your name?" "Hello [name], how are you feeling today?" "I'm glad you're feeling [feeling]!" etc

And I had the companion radio shack cassette deck that you could use to store programs on. I always had to copy those programs out of the book because I didn't understand them at all.