The ZX81 was my first computer. I remember writing an adventure game, but because I only had the basic 2k RAM, each room in the game was a separate program that was saved to tape at a specific tape counter location. Then, when you made a decision in a room, it would ask you to wind to a specific tape location to load the next room. Got played once, by my brother, but I was pretty proud of it.

Soon after I got a job as a student working at an astronomical observatory. The director had just bought a ZX81 for his personal use, and when he heard about my experience with the machine he gave it to me along with an article describing how to reduce photometric data. This time I had the luxury of the 16k RAM pack, so I wrote the whole thing, including data reduction, graphing, analysis in one app. Lots of fun accidentally knocking the RAM pack and losing everything multiple times. Once it was done and demoed, I was asked to publish it. However the observatory did not pay up for a printer so I had to use a typewriter to bang out the code for the article, meaning of course there were plenty of typos. Got amateur astronomers from various countries using different machines trying to get it working. Back in the days of paper envelopes with source code printouts to debug.

Good memories, and the launchpad for my programming career.