When my school's first Commodore PET was stationed at the back of my form classroom, I managed to find myself a seat where I could get to it before anyone else and spent breaktimes and hours after-school figuring out how it worked. Since the manual was next-to-useless I had to rely on BASIC program listings in home computer magazines to figure out how to get it to do stuff (the school had a few games on cassette but we were forbidden from playing them). Initially the things I wrote were all simple branching text adventures ("You see a corridor running west to east. Which direction do you want to go?"), but eventually I figured out enough to be able to POKE ASCII character codes into screen memory locations without crashing it. I made some very basic arcade-style games that way, and I still think fondly of those terrible square keys and that green screen.
The first time is the one you remember: first crush, first kiss and first BASIC program. These are the ones that stick in your mind long after those involved are no longer around, and the Commodore PET was the first computer that many people actually touched. Before the PET, computers were big, impersonal things that people worshipped from afar. After the PET, the computer became personal.