My first computer was a Commodore Vic-20. My mom bought it for me in 1982, I think, when I was 14. I remember thinking, what the hell am I going to do with this? I don't think "hello world" was around then, but I followed the manual and ran a goto loop and printed something on my TV through the RF receiver, and, of course, I was hooked instantly. I bought a book entitled, "Programming the 6502," which came with a handy schematic of the processor, and learned that computer from the inside out.
I even breadboarded a memory expansion to it. It only came with a few kilobytes, and to get a few more you had to buy this cartridge that plugged into the back for something like 30-40 bucks. It was a long time ago, but I think I just bought a few static ram chips at radio shack and got the same amount of ram for about 5 or 6 bucks. Me and a buddy of mine were going to go into the memory business after discovering this but got sidetracked with adolescent issues.
I don't still have the Vic-20, but I have the original breadboard memory expansion prototype and a few photoetched circuit boards in storage somewhere. Lol.