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.