There‘s HP calculator guys and TI guys. Around the age of 17 I spent lots of time programming my HP28s calculator in a Forth like language that had symbolic mathematics, lots of ideas from Scheme (closures, functions as first class arguments, recursion). It felt like magic dealing with concepts I hadn’t seen in the C compiler on my Amiga or later in Turbo Pascal. But I saw these concepts later in Mathematica and was familiar.

I had programmed games, complex 3d visualisations (super slow but oh well), and was totally fascinated by what this device could do.