I had a VIC20, and I wanted a way to print out my programs and some output. I bought a cheap 25x80 column thermal printer and interfaced it to my VIC20. I wrote

I had a VIC20, and I wanted a way to print out my programs and some output. I bought a cheap 25x80 column thermal printer and interfaced it to my VIC20. I wrote a program that showed the position of Jupiter's four large moons - Io, Europa, Callisto, and Ganymede. The calculation was based on a formula in Peter Duffet-Smith's book, "Practical Astronomy with your Calculator". They came out with a similar book after with code in BASIC, which I bought too. They were both little sprial-bound books that I have since lost thirty-plus years later on. The thermal printer was fun to print and bring snips of code to computer club meetings later in high school. I even had it print an PETSCII or revised Commodore ASCII representation of the positions of the moons relative to Jupiter. The only issue is that the thermal print would fade, so I would reprint the faded ones when I could.