They haven’t been produced in decades, but [Chris Chung] has used some open source code to create DIY hardware version of the HP-41 Reverse Polish Notation (RPN) calculator. The open source code ...

To play Tic-Tac-Toe against an HP-85 computer or an HP-41 calculator, you can use one of the emulators listed below. Of course, the preferred and funnier way is to play it on real vintage hardware! If ...