10 years old, I suppose. The school I was at got a couple of ZX81s donated by Sir Clive himself (not that he was a "Sir" then) and set them up in what felt like a converted bike shed. A few months later, I got my grandfather's cast-off ZX80, and bought my own ZX81 shortly after.

I use "MasterList Professional" from Safari Software. Works well for single-user stuff, 45 day free trial, costs a mere US$25. Gives the "green" and "red" statuses as well as a few more. MS Access database at the back, totally open so you can add your own code bells and whistles. Bob says he's working on a Team version, but he's been a bit distracted with other things...