Wall Street's Cult Calculator Turns 30

Concatenative languages like the HP RPN offer a nice gentle introduction to programming. In fact, I'll go further and say they trick you into programming without even realizing it. One minute you're working through a calculation for the Nth time via the same series of button presses, the next minute you're recording those button presses into a new user-defined button, and moving on to some higher level calculation. I've seen people do this and think they're "just calculating," when in fact they're doing bottom-up programming.

Here's an example if you're not familiar with HP RPN. Say you're performing a repetitive computation like finding the euclidean mean with X and Y already sitting on the stack. These are the buttons you push:

  DUP * SWAP DUP * + SQRT

  << DUP * SWAP DUP * + SQRT >> 'L2NORM' STO

This natural progression from calculation -> programming is something I miss in other languages. I like the idea of concatenative languages [1] like Factor, Joy and Forth, but hesitate to embark on anything more than trivial programming with them; their terseness can be even more extreme than Lisp's.

[1] http://concatenative.org/wiki/view/Front%20Page

I think they've even released an SDK for it, if you're into reflashing with your own code...

I was taking the final, and the professor lent me his calculator. It was an HP RPN, and he said he didn't know how to use it. I figured it out quickly enough -- as a computer guy I know how stacks work -- and went to town banging out calculations on that thing in record speed.

Since speed is an essential part of test-taking, and I was notoriously slow at doing calculations, I was at real risk of flunking the exam and the course. As it is I saved my bacon. Thank you, HP! Thank you, RPN!

I disagree with the wristwatch comparison. I'm in my twenties, and I still rather like having a watch. Checking a wristwatch is much, much, more convenient than pulling a cellphone out of a pocket, activating its display, and reading the time. Especially when outdoors, I'd much rather rely on a wristwatch for timekeeping than a cellphone. I can drop a cellphone. I can't drop something that's tied to my wrist.

Imagine how great it seemed when it was not only a beautiful thing, but also the last world in technology.

Full disclosure: I'm something of an HP calculator nerd. I have an 11C, a 15C, a 16C, a 32SII, and a 42S. Once you get used to RPN, you will never want to go back to algebraic calculators.

[1] http://www.hpmuseum.org/hp16.htm

It runs on an unconventional operating system called "Reverse Polish Notation,"

Now I need to go and dig up my 15c

HP 28C (http://www.voidware.com/calcs/hp28c.htm): Mid 80's through mid 90's

Emacs calc mode: Mid 90's through mid 2000's

orpie (http://pessimization.com/software/orpie/): Mid 2000's through present

If you're an old HP calculator user go check out orpie. It's an RPN calculator for the console. It doesn't appear to be actively developed. Still, it has already got everything I want in a calculator and works very, very well.

When I got my first real engineering job, you could tell the age of the engineer by the era of HP calculator on their desk (or frequently in their hand). One guy had one with red 7 segment lights and 4 slots in the back, lots of guys had the engineering version of the 12, I had my 28S, and a couple young-uns had the 48. There was one guy with a TI, but he didn't last long.

I find I'm a lot better with the 28 with it's 3 or 4 visible stack items than the single visible one of the smaller calculators. But it is a lot bulkier, and i teats batteries. I think I've had to replace them 5 or 6 times in the time I've owned the thing.

"...is the only other calculator test-takers are permitted to use on the official CFA exam"