I’ve built up a collection of calculators over the last few years after getting a HP 35s for the FE and re-discovering calculators as a distraction free study aid. Nothing wrong with collecting stuff, we all do it at one point in our lives and calculators are compact and relatively cheap. Here’s my current stable, roughly in order of aquisition:

  1. HP 35s
  2. TI 36x Pro
  3. Casio 991EX ClassWiz (sold)
  4. HP Prime
  5. HP 12C Platinum 2nd gen
  6. HP 10bii+
  7. HP 17bii
  8. TI baii plus
  9. SwissMicros DM42

HP 35s

I bought this for the FE. It gets a lot of hate for the long buglist which is unfortunate, as the hardware is nice. I’ve heard an unfortunate story that HP subcontracted the firmware design out but the contract terms didn’t give HP ownership of the firmware or at least the source code. Hence over 10 years after introduction the bugs still exist. This one has the better feeling keys of any recent HP I’ve owned, coming in just after the much underrated 10bii+. I like that the big enter key is center-left compared with the Prime, which has it on the right, inconvenient for right-hand use. My main annoyance is that pressing the EEX key without a mantissa will result in an error rather than assuming a mantissa of 1. Some of the ordering of menu items doesn’t make much sense, particularly the clear menu, where CLX is entry number one despite having a dedicated key, but CLSTK is on the second page. Compared with its competitors the TI 36x Pro and Casio fx-991EX, it feels a bit dated with its character-only display and lack of numerical differentiation, matrix operations and a polynomial rootfinder. For rootfinding at least, I’ve found the numerical solver to a decent substitute, but don’t expect it to be as fast as the bad-boy fx-991EX which I understand to be as fast on integration as some early 2000s era graphing calculators. It does have an elegant method for algebraic equation entry which allows equations to be shared with both the solver and numerical integrator. It might not be as flexible as the HP42s solver, but it’s a reasonable tradeoff for ease of use. There’s also solvers for simultaneous linear solutions of 2 and 3 variables. Between this and support for up to 3-element vectors on the stack, the lack of matrix support is mostly compensated for. Not being familiar with older HPs I was suprised to find out that this is a programmable calculator, though the macro-style programming is a bit clunky and programs have to be entered manually as there is no USB or any other kind of port. Such is the price for FE acceptance.

Casio fx-991EX (Sold)

I really wanted to like this calculator even if it’s an ugly beast. Currently it’s the most capable non-programmable calculator in the US market, and will remain so until such time as TI brings the 30x Pro MathPrint to North America. Unfortunately it is held back by Casio’s software limitations. Like the 30x Pro Mathprint, it does have a higher resolution screen compared to the TI 36x Pro which is nice for longer expressions. I think the screen is actually only about 64x196 pixels or so, but that goes a long way on a little calculator screen. Also like the 30x Pro Mathprint it can handle 4x4 matrices and calculate roots of 4th order polynomials. The processor is a minor miracle for what it can do on 600 microwatts and is quite fast on numerical integration benchmarks. The keyboard layout is efficient with helpful dedicated keys like the ENG key to quickly enter powers of 10. It’s limitation is that it is difficult to re-use results, especially as it clears history on mode change. I assume that this is to meet testing requirements in either Europe or Asia, though I don’t get why matrix/vector variables don’t get cleared.

TI 36x Pro

This calculator is starting to show its age compared with newer offerings like the Casio fx-991EX, but it’s still a hidden gem in the TI lineup, especially since (as of 2020) it sells for around $18. If you’re not into RPN, live in North America and can’t use a graphing calculator, this is the guy to get. I have an old one I use for wood shop duty. It’s ability to handle fractions is nice for calculations with imperial units which makes it useful for measuring lumber. It feels like a baby TI-89, but without the graphing, CAS and programming capabilities. Repeatedly pressing keys cycles through functions without having to reach for the “2nd” key. This is nice for things like sin() and asin(), but having one key for all 6 variable names is annoying and a poor choice. Better would have been the more common solution of a dedicated “x” key and an alpha layer for other variables. The silver keys for common operations are hard to read, but the key locations are standard so it’s not the big deal it’s made out to be. Key feel is about par with Casios but not as nice as clicky HPs. Re-using entries and results from the history (which is retained through power cycles) is easy and one of the best things about this calculator. I’ll confess that I’ve never found the need to do stats calculations on a calculator, but the dataset editor is pretty neat and a lot nicer than the HP approach of using accumulators as it lets you check your entries afterwards.

HP 12 C Platinum (12CP)

While I like RPN, I don’t quite get how this guy has hung around for so many years given its limitations compared to newer models like the 17bii. If you want to try out a Voyager series calculator but don’t use trig functions much and don’t want to spend $150+ for an 11C or 15C, there are tons of 12Cs of various generations available on Ebay. The Voyager form factor is pretty nice and has a cool 60s retro vibe to it even if it dates back to the early 80s. The 7-segment LCD display has great contrast. There are a lot of dated design choices that hold it back though. My main gripe is that there isn’t a good scroll through entries when doing cash flow calculations. Entries can be recalled individually using the number keys but there is no easy way to do this for the number of occurences. There is a way to iterate backwards through the cash flow entries but it’s pretty clunky and involves shifted keystrokes for each iteration. Another annoyance is using the n register as an index when recalling cash flow entries, which seems like asking for errors. A smaller complaint is that while the 12CP adds a backspace key, it’s shifted while CLX remains the primary function. The hardware quality on the unit I got was OK. The keys seemed a tad mushy compared to my other modern HP calculators (10bii, 35s, Prime) but not bad. Some folks have complained that the plastics seemed of poorer quality compared to previous generations. The body on mine felt OK, but I did notice that plastic on the blue/orange shift keys seemed to be lacking the opacifier in the dye mix and came out slightly translucent.

A bit about 12C versions

There seems to be a bit of confusion here, so I’ll go over my understanding of the model breakdown.

  1. Original 12C: Great build quality and keys. The sub 1 MHz CPU is great for battery life but slow on some time-consuming calculations like IRR, which can take over a minute to complete. This takes 4 LR44 batteries.
  2. Single CR2032 12C: This came out somewhere around the millenium and uses lower-voltage silicon. Processor speed is unchanged. I’ve heard build quality is a slight step down. This the unloved version though there is nothing really bad about it. If you use it a lot you might save a couple dollars every couple years on batteries.
  3. 1st Gen 12CP: This re-implements the original software in C on a 32-bit ARM platform (which seems to be the standard for all modern calculators). There are a couple bugs regarding some operations not enabling stack lift, but it’s nothing like the long bug list on the 35s. Execution time is reduced by about a factor of 4 compared with the 12C. This has a silver faceplate compared to the somewhat tacky gold one on the 12C and adds alegbraic input mode plus a backspace key. It is also the first unit to use two parallel CR2032 batteries.
  4. 12C+: I guess folks had a lot of complaints about the 12CP so this version runs the original software in emulation on ARM. Wild! Supposedly this is actually faster that the 12CP, despite the software running in emulation. Like the 12CP, this uses two parallel CR2032s. I’ve heard there is a high rate of key failure on this variant compared to the 12CP.
  5. 2nd Gen 12CP: This adds parentheses keys for algebraic mode. I think there is a different processor, but not much of a speed difference.
  6. 12C++: Supposedly there is a 2nd generation of the 12C+ that uses a slightly different processor, though speed is about the same.

HP 10bii+

It’s not RPN, but I’ve found it to be an underrated gem. The key feel is my favorite on modern HP machines. There is alleged to be a fairly high key failure rate but nominally the keys work fine. As an aside - it’s just not reasonable to expect the same level of build quality as the Pioneer or Voyager series, this is a sub $25 unit and the quality is fine for the price point. HP did a really good job of taking the features people liked on the TI baii plus like the addition of trig functions. At the same time the UI is a lot more efficient with many less key presses required. Surprisingly, I found the baii plus to be only slightly more intuitive, and the only real advantage I’ve found is that the baii has a alphanumeric section on the left of the screen to indicate the type of calculation performed. This unit is also quite fast, I believe it is also ARM based and noticeably faster than the baii.

TI baii plus

This has taken over from the HP 12C as the standard financial calculator for coursework. It’s more user-friendly than the 12C but still leaves a lot to be desired UI-wise. This isn’t anything like the excellent 36x Pro where most functionality is discoverable by pressing keys, you will need to read the manual for this machine. There are a lot of quirks like the oddly placed on/off key and the backspace key pointing the wrong way. What probably best sums up my annoyance with this calculator is that it has both an equals key, enter key, set key and compute key all of which have separate but similar meanings. There’s also a heavy dependence on modes, so things like setting begin/end mode involve entering and exiting a special mode just to toggle that particular setting. The 10bii is much more effcient with keystrokes but without much a penality in terms of inuitiveness. Software complaints aside, the hardware is intentionally limited with the intent of upselling professional users to the pro model. Pro features include rubber feet and better keypress scanning. The main complaint of this unit is that it regularly misses keypresses. This isn’t being picky, I found myself having to frequently make corrections on account keys not registered and I’m not particularly fast.

HP 17bii

If you want to try out a Pioneer series calculator but don’t use trig functions much and don’t want to spend $100+ on a 32sii or $200+ on a 42s, give this guy a try. I bought mine for about $20 on Ebay and it’s in excellent condition cosmetically. It lacks programming cabilities but has a nice solver and calculation speed is good even compared with modern ARM units. I really like the software on this guy compared to the baii plus and 10bii+. The menu-based interface keys the keyboard looking pretty clean and the dot-matrix display allows for displaying the type of calculation computed reducing the possibility of errors. I really like the cash-flow entry system which allows for toggling the entry of number of periods for a value. The dot-matrix display does have terrible contrast compared to modern or even later units but it’s still plenty readable. The big issue with this model is that it’s about 30 years old and parts are wearing out. Despite mine looking great, the keys don’t feel as good as even cheap newer units like the 10bii.

HP Prime 2nd Gen

This has become my go-to-calculator. The software isn’t as mature as on the TI N-Spire, which has much better integration between components and a slightly better CAS, but I’ve found it to be a good jack-of-all trades by combining RPN input with a pretty good CAS. It’s also priced competitively so this takes my recommendation for what to buy if you want just one calculator, assuming no exam restrictions. I used an HP 48GX back in high school, which felt like secret military technology at the time. Later in grad school I got a 50G. I kept hearing good things about the Prime, so I wanted to see what the latest in the HP stable had to offer. One criticism I keep hearing is that it’s done away with the elegant “everything-works-on-the-stack” approach of the 48/49/50G, and introduced Casio-style modes. I don’t love or even like the Casio modal interface, but it seems to work here as it allows for algebraic entry when using the CAS and RPN when doing numeric calculations. I’m less convinced of the benefits of having separate symbolic/numeric/graphing views in the apps. Some other nitpicks: I prefer the enter key on the left-hand side like the 48G and 35s, but at least it’s big and center mounted instead of being relegated to the bottom-left-hand corner like most calculators. I don’t like that the hardware function keys been dropped in favor of virtual ones on a touchscreen, but the capacitive touchscreen is actually pretty good I and I quickly got used to the virtual keys. The context-sensitive help is very good, and keeps me from reaching for a computer and thereby removing the benefit of a dedicated calculator as a distraction/social-media-free study/work aid. Also, try scrolling a function on the touchscreen - it’s fast! Actually, everything on this guy is pretty fast. Overall, this actually feels like a modern-ish computing device while still being a graphing calculator.

SwissMicros DM42

I don’t get the hype around the HP RPN scientific calculators. They are well made machines, but limited and quirky compared to the later 48G series which have more predictable behavior with dynamic stacks and a dedicated input register. However, I do like the idea of a bespoke calculator in the vein of the Teenage Engineering OP-1. I don’t care for the faithful recreation of HP 42s behavior, but I do like having a device that is fairly bug-free and which can make use of the large existing library of HP 4xx programs. Finally there is a 4xx-compatible device with USB connectivity so programs can be loaded without having to type them in. Browsing HP software repositories hits my nostaligia buttons pretty hard and makes me long for the pre-social-media days of the internet. The much-complained about keyboard is OK but really should be improved, though I’ve fallen in love with the big high-contrast LCD that shows the whole stack at once and marks this as a premium product. I have a collection of programs available for the DM42/Free42/HP42s here:

https://github.com/akbarnes/hp42s

Elektronika MK 52

This is an odd beastie, an RPN calculator made at the tail end of the Soviet Union from 1983 to 1992. There’s a number of deadstock units avaiable on Ebay for cheap. A lot of them don’t work as on account of poor manufacturing quality the VFD’s often go bad. This includes the one I bought. I thought about trying to get a working one, but despite allegedly going to space on Soyuz, the keypad quality and build quality in general is so poor I doubt I’d ever actually use it. HP’s these are not.

Elektronika MK 52