HP 35s

My HP 35s sits between the 2 halves of my split keyboard. I use it multiple times per day. It's just faster for quick calculations as the UI is very well done and it turns on instantly.

HP did license out the manufacture of 12cs at some point so if it's not a counterfeit it is almost certainly a manufacturing error by some licensee. Note that the 12-c is one of a legendary "voyager" series of HP calculators which have that landscape form factor and are highly prized by collectors. There is an HP15-C scientific calculator equivalent and a 16-C which is supposed to be for programmers so does the sorts of things we programmers do all the time like converting things from hex to octal etc. It has built-in support for bit twiddling and shifting operations too. If you ever see a landscape-style "voyager" HP calculator in a junk shop or whatever and it's not a 12-C (because they are quite common) it's quite rare and may be worth buying and reselling if it's in usable condition. I have 2 HP-12c calculators which I bought while I worked at Goldman. One was always on my desk at work and I had another at home. I can certainly confirm they were common in finance back in 2000-2009ish. That said even back then they were being replaced by non-RPN calculators for a lot of people and only people with nostalgia and the hardcore had a 12c. They're incredibly robust - famously a zookeeper once used an HP12-c to calculate proportions for animal feed, dropped it into the mix and it passed through the digestive tract of a hippo. It was still able to calculate the yield to maturity of a bond after cleaning. In addition their batteries last forever. Even though the versions I ha…

Not as much fun as the real thing. I've owned several HP calculators, going back to the 1980s. My 15C might be my favourite, actually, although my 35S is similarly pleasant to use. Frankly, though, the loveliest were those early-era ones that had rounded backs that were so comfortable to hold and use with just one hand. For me, they are the true classics for use in the lab or the field. I also used a large desktop as a student. It might have been a 9100, but I'm not sure. The keys were great (always a prime aspect of HPs) and it was hooked up to a little plotter that was very handy for seeing what a complicated function looked like. Come to think of it, the only non-HP calculator I ever used was a Sinclair Scientific. It was really fun, but it only lasted a few years before it had electrical problems. But for one-hand use, it was amazing. And it was tiny and weighed very little. It had a sweet little plastic case to protect it, so you could put it in a pants pocket with keys and there was no problem. Good times with RPN.

The boot-up time is really a killer. I also just can not get used to the input/keyboard of the nSpire. My actual workflow is to use DM42/HP-35s for anything I can do with those, and if it's more complicated, I'd rather launch Octave or MATLAB. I just can't make my nSpire work for me.