The first computer I was exposed to (hmm, that sounds dirty) was a mainframe system at University of Virginia back in 1979. I don't think I ever knew what kind of system it was (I was 9 years old) but it was where I learned BASIC. I do remember using a terminal that didn't have a screen. Everything I typed showed up on paper... followed by a response. It was the coolest thing I had ever seen. The last thing I did every day before leaving the lab was to do a complete program listing of whatever I worked on.
Having a mile long perforated and tractor-fed record of everything I did gave me plenty to study after I left the lab. I would take it home, make notes on the side, and trace the execution line by line with my finger. Playing the games in my head, over and over...
After that summer, and for the next year, I wrote a lot of computer programs that I didn't have a chance to actually run anywhere. The year after that, I started Junior High (they call it Middle School now... sigh) and met my first TRS 80 Model III, and my first obsession: Raaka Tu. I can't tell you how many hours I wasted on that game. Even after I solved it, playing it again and again.
The first computer that was actually mine was a TRS-80 Color Computer. It used cassette tapes and cartridges and had a whopping 16k of RAM and used inverse characters for lowercase (green on black instead of the "normal" black on green) display. The graphics modes were really primitive and you had to use machine language for any kind of performance. We had a color TV but there was no way my dad was going to let me tie it up for hours at a time with my computer, so I inherited a small black and white tv for my room. I actually had no idea how bad the color palette was on that computer until a few years later when I hooked it up to a real monitor. All I had ever seen was shades of gray until then, so I just assumed it was better than it really was.
Eventually I got a floppy drive (at the bargain price of about $200) and hooked up with my first user group. Back then, they were little more than copying parties and hardware swaps. Once I got that floppy drive, I was a man on a mission. I spent a lot of time in Radio Shack as a kid. I'd go in with a buddy and he would chat up the sales guy about RC cars and ham radios and stuff and I'd be at the computer copying all the games as fast as I could before he got back.
All my friends (that had computers) had Commodores and Ataris. They had all the cool games. There were a fair number of games available for mine too, but nothing like those systems... as a result, I wrote a lot of my own games.
I've been writing code ever since.