WP 31s

A perfect daily driver RPN calc.

Very clean and well organized scientific calculator, pleasure to use.

For those of us who find it harder to use a standard calculator, this is a godsend. The old hp calculators were truly the best and I still use my 32s II daily at work. I use this calculator for everything else in between. Hats off to the developer for such a great app!

Works very well. Version 1.8 looks great on 2017 iPad and iPhone X. Full screen scaling and auto rotate work. With IOS 14 on iPhone 6S: the app fills only about 75% of screen in portrait mode; won’t auto rotate. Reinstalling had no effect. The app is still very usable.

Only thing to make it better: haptic feedback on key press!

Very nice design of a straightforward scientific calculator that gives immediate keyboard access to all the basic scientific-math functions (roots & powers, trig, logs and exponentials, etc.) and then also gives unusually quick access to many more, through several generous menus only one level deep for stats, distributions, numerical constants, unit conversions, and more. It isn’t programmable; for that you may want the big brother, the WP-34s, which is not only programmable but substantially more powerful and elaborate. The -31s devotes its layout, instead, to making the basic scientific functions accessible as simply as possible. And there’s no implementation of complex numbers; for that I recommend the HP-42s, or Thomas Okken’s excellent Free42 emulater of it, or now the Swiss Micros DM-42 that runs Okken’s code. An example of the WP-31’s quick keyboard design is that there’s a prefix key “HYP” that lets you get hyperbolic functions from the trig keys without diving into a menu. Elsewhere (at least in the RPN world) I’ve only seen this on HP’s 11c, 15c, and 32s/sii, and three emulators — Vicinno’s 11c/15c and Ernest Brock’s All-RPN for iOS. Another little touch that I like, as an engineer, is that both “ln” and “e^x” are primary functions of their keys (not shifted functions), which I’ve seen elsewhere only on the 32s/sii. (And on Brock’s All-RPN, where he buys more keys by shifting the whole keyboard between math, trig, etc.) The WP-31s and its big brother the -34s are originally hardware boxes, created by writing new firmware to flash into the plug-accessible PROMs of the HP-20s or -30s business calculators. In the iOS ports of the WP’s, though, the designers have redesigned the menus as pop-up lists to take advantage of the touch screen, which makes them way faster to use — the first time I’ve seen large menus that aren’t a major bottleneck. Being derived from the -34s, the -31s has some features more advanced than you’d guess from its utilitarian keyboard. First of all the big menus, of course; also the choice of giving the stack eight levels if you want more than four (the touch screen lets you swipe down to see all of them, plus all the other registers too); and a thoroughly-worked-out display mode for fractions; maybe other things — do download the 50-page manual offered in the Help screen. The WP’s do have a kind of odd screen layout because, as emulations of the hardware versions, they reflect the rather dorky layout of the HP-20s/-

Was really bummed that my paid HP-15C app has not been updated in 4 years, and might not even work on the next iOS revision. But after finding this free WP-31s app, I might never need to use the old one again. The layout is simple and clean, with keyboard access to all the functions I need on a daily basis. (And menu access to plenty of functions I might or might not ever need!) A heartfelt thanks to the developers!

As a LONG TIME user of RPN (i.e. HP) calculators, this one is very familiar feeling. So far it has performed every engineer calc I've tried. I'm very impressed and pleased.

It's the perfect calculator I never knew existed. RPN, non-programmable (for exams), and easily accessible time calculation. Great to use on iOS, I even got it in hardware!

My hats off to the developers of the WP34S and WP31S calculators. This is a faithful emulation of the WP31S. Teach your kids RPN this PI day!