I had an HP28c ( https://www.hpmuseum.org/hp28c.htm ) that saw me through high-school calculus and undergraduate work. In it's day, it was a revolutionary product.

I never got to play with the data sharing stuff, since none of my classmates had such an expensive or geeky piece of kit (I got mine used, but it was still expensive).

This is the correct answer. I'm still sore over someone stealing my HP-48G near the end of my last year of university. Though I'm looking forward to getting a SwissMicros HP-16 clone for my embedded projects...

https://www.swissmicros.com/

Heh, and keep imagining after you get one. The range is extremely poor, even an inch is tough. It's so limited there's an arrow on the calculator so you now EXACTLY how to align the calculators for a transmission. No way a reflection is going to work.

I had an HP 48g for some time and I loved the feeling of the buttons. It did take a long while to get used to the reverse polish notation. Sadly that calculator died on me. I still use an app on my phone as the go to calculator.