[readingnews]

I have an old HP 15C RPN scientific calculator.

- I know where the buttons are without looking.

- It has functions my Android calculator does not have (directly or that I know of).

- It has a strange satisfying tactile feedback.

- It never interrupts me. Ever.

- It never distracts me. Ever.

I reach for it frequently.

[commakozzi]

IMHO the HP 15C RPN is the best calculator ever made. I still have the original with the slip case and manual. However, more often these days i just use my phone's calculator without RPN (i don't need to do a lot of complicated math for mechanical engineering -- we use tables for most stuff). I reached a point/decision several years ago to protect my HP 15C for posterity.

[rented_mule]

I can't think of another electronic device that has survived and remained useful for half the 43 years my 15C has - through two years of high school, a math degree, and an entire software engineering career. When I calculate something any other way, it involves thinking about what my thumbs automatically do on my 15C and translating that.

When I'm away from it, there's a wonderful emulation of the 15C (and 16C) at https://jrpn.jovial.com. The numeric algorithms behave identically as far as I can tell, and it even includes the back panel (3-dot menu near the logo, then "Help"). The visuals make me feel right at home. If only they could reproduce the tactile experience.

[silvestrov]

I've never owner any other piece of technology with buttons this good.

It is really a lost art.

[pseudohadamard]

I have some generic Sharp calculator with an apparently-immortal battery and a nice multiline display. It has all sorts of fancy functions that I never use. Apart from that, everything the OP said.

[kqr]

I smilarly use the HP 12c. There is nothing more convenient for solving simple compound interest/discounting problems.

[zippyman55]

I still have mine too! My non-techncial wife learned to use it, and I smile everytime she used RPN.