For me, the ultimate HP calculator was the HP41CX. You could even hack it using a technique called "synthetic" programming. http://en.wikipedia.org/wiki/HP-41

For me, the ultimate HP calculator was the HP41CX. You could even hack it using a technique called "synthetic" programming. http://en.wikipedia.org/wiki/HP-41 http://en.wikipedia.org/wiki/HP-41 I even had the magnetic card reader so I could store programs. In my opinion, RPN gave me a big speed advantage at school during exams.