First post on Lemmy, and i see you like pens too :)

Sorry the angle is a little funky, but this is one of my two workhorses, the Casio BN-20. This guy gets used almost every day, and is my primary source of truth for my calendar and contacts. It was released in 1998 and has 2 MB of user memory. The spreadsheet function is pretty rudimentary, and the only function that I don't have a lot of experience with. The expense function is the best expense tool I've ever seen on an electronic organizer. I run Xubuntu on modern hardware and can sync the data using Casio PC Sync through Wine and with a USB to serial converter.

Someone gave this to me 15 or so years ago.

Not really a calculator, but I saw that someone posted a series 3 :)

I wish this form factor was still a thing.

Yeah, I know Gemini exists but the software is already rotting...

A gift from my Calculus teacher upon graduation.

Yes manual included. Sadly the 0 (zero) button no longer works, due to battery corrosion... ☹️

This is the calculator that got me through junior high and high school. It even handles fractions, which is what you see on the display there.

355/113 is a very close approximation of PI, accurate to 6 decimal places.

Yes the calculator also has a proper constant for PI, but 355/113 is a pretty nifty trick in it of itself.

355/113 = 3.14159292, at least on this calculator.

This example was manufactured on the 7th week of 1979.

https://www.calculator.org/calculators/Texas_Instruments_TI-30.html

The Curta mechanical calculators were designed by the Austrian engineer Curt Herzstark, with initial designs from the early 1930s – being half-Jewish, he finished the design while being held prisoner at the Buchenwald concentration camp.

Here's some quotes from the wiki article:

While I was imprisoned inside Buchenwald I had, after a few days, told the [people] in the work production scheduling department of my ideas. The head of the department, Mr. Munich said, 'See, Herzstark, I understand you've been working on a new thing, a small calculating machine. Do you know, I can give you a tip. We will allow you to make and draw everything. If it is really worth something, then we will give it to the Führer as a present after we win the war. Then, surely, you will be made an Aryan.' For me, that was the first time I thought to myself, my God, if you do this, you can extend your life. And then and there I started to draw the CURTA, the way I had imagined it. — Curt Herzstark, Oral history interview with Curt Herzstark (1987), pp. 36-37

[…]

The Curta's design is a descendant of Gottfried Leibniz's Stepped Reckoner and Charles Thomas's Arithmometer, accumulating values on cogs, which are added or complemented by a stepped drum mechanism.

Numbers are entered using slides (one slide per digit) on the side of the device. The revolution counter and result counter reside around the shiftable carriage, at the top of the machine. A single turn of the crank adds the input number to the result counter, at any carriage position, and increments the corresponding digit of the revolution counter. Pulling the crank upwards slightly before turning performs a subtraction instead of an addition. Multiplication, division, and other functions require a series of crank and carriage-shifting operations.

My last acquisition has finally arrived. I am very happy

My 71B is telling me "Data Error" whenever I try to use the variable "F" - any ideas?

Calcula is an RPN calculator with 26 stack levels and 26 storage registers. It is not programmable except you get the Pascal source code and you can create new, possibly complex, functions for the calculator.

https://gitlab.com/waspentalive/calcula

I am looking for suggestions for other functions to add and testing for the existing functions. Free. GPL3 License.

This Casio took me through school, and most of uni. Well battle worn, still working. Please dont send me to calculator jail xD.

I've had this guy for about a 18 months and it is one of my favorites. It is slower than the HP Prime and the TI-nspire CX II CAS, but still blows the TI-89 Titanium out of the water as far as speed goes. The huge touchscreen gives it a unique UI that is easier to navigate than the TIs. I've found that this is the best of my collection for linear algebra, and it is the easiest of my CAS calculators to use.

You can see the bits moving around inside when you use it.