Defining parallelism and concurrency

My first computer was an HC-90, a ZX-80 clone built in Romania. I owned two versions: the first required a cassette player to load programs. Despite this inconvenience, it had a big advantage over its main competitor at the time, the CHIP computer, yet another ZX-80 clone built in Romania. You see, the CHIP computer required a cassette to load into its OS, while the HC-90 had enough EPROM memory to boot directly into a BASIC interpreter. The second version I owned was much better: it had a 5-inch floppy disk reader, which meant that you could load programs much faster.

In both versions, the BASIC interpreter was your interface with the computer, and since not many programs were available other than games, I spent some of my time in high school writing BASIC programs and playing games. Eventually, I realized that I wanted more than BASIC. I played a bit with graphics and sound, but the problem was that everything was very slow. This made me learn...