I wrote programs to draw graphics. It was common to have a function that would plot a line between two screen co-ordinates with a certain color. I learned how to put these into loops, changing the parameters each time, and getting really fun results. The joy of these machines was ( especially the Commodore 64 and such ) you could just turn it on, it booted in a few seconds, and you could start coding right away, at the prompt. There was no overhead, you just did it.