Working Things Out Backwards

[krpalmer]

After reading a book about calculators and then a weblog post about a brief slice of their history when pocket electronic machines became available in the early 1970s, I happened on an emulator program for some of the first Hewlett-Packard pocket devices. That got me thinking about their particular method of data entry, and whether I’d brushed by “Reverse Polish Notation” just because of the unfortunate potential for inappropriate smirks. I did get to the point of looking up the manual for the HP-35 calculator, the original “electronic slide rule,” and then I started searching in my phone’s “App Store.” One free application offered the layouts of the HP-35 and two of its immediate successors, the enhanced HP-45 and the cost-reduced HP-21. It did offer “haptic feedback” when you pushed on-screen buttons, but when I realised it didn’t quite offer the multiple memory registers of the HP-45 I started looking at calculator programs you had to pay for. One person offering quite a few programs had a “free sample” ready in the form of the HP-70, a simplified financial calculator, and that was enough of a preview for me to buy an HP-35 program for my phone and a HP-45 program for my iPad.

Once I’d become used to it I could see how “RPN” entry worked with complicated calculations; the question was just how many of those complicated calculations I actually do. I also got to the point of thinking I ought to see if I could still multiply and divide by hand on paper, and found myself prone to errors while multiplying at length. My only hope is that practice would help there.

Comments

[mmcirvin]

The calculators I eventually settled on in college and grad school were HP's RPL line, the 28S and the 48SX (the latter got stolen--it was too expensive to leave lying around). There were several later models. Eventually HP open-sourced the firmware for them, so a lot of free mobile emulators exist--and these were the most powerful calculators they ever released, though RPL subtly changed the way HP's RPN calculation worked in ways that were not to everyone's taste.

But RPL was a great programming language, sort of a strange cross between LISP and FORTH--it gave the stack unlimited depth and allowed putting everything from graphical objects to programs on it, instead of just numbers. In some ways it was a functional programming language. These calculators also introduced some CAS capability: they could do symbolic algebra and calculus to a limited degree, though it was a bit cumbersome compared to what you could get for a computer.

These days, I don't use all of those capabilities on a regular basis, but a 48GX emulator is my go-to calculator.

Those are all much later models than the ones you're looking at, from the late 1980s and early 1990s, with multi-line LCDs and graphing capability.