I really loved learning how to push this little gem to its limits, so many tricks were possible with the weird addressing schemes.
(I wrote a hobby OS for the HP48 series when I was a student)
I myself had an hp48 during my high school and now I own 6 of them I bought on Leboncoin or eBay for cheap. Also found an hp32sII for 5 euros but after three years I own it it decided to die in my hand.
Most of the models seems to age well except for the rubber-like connector between the key plane and the motherboard, and the keys are either not registering presses or you have to press hard on the body.
If it would have supported normal notation as well it would still have been a useful tool to me.
I have a serial cable and was able to upload program on it ( the famous dune game) I also grabbed some French books (classic one for hp48)
Diamonds was also very good.
My little collection
I had most of those books and a few others at some point.
My almost 30 years old GX was unfortunately stolen last year. :(
Didn’t know about Diamonds. Something to look up. Thanks!
Also, the model was popular in preparatory schools because of the expansion slots, it was possible to extend the memory by a huge margin.
This memory was useful to store, well everything you could, and at the time those calcs were not forbidden during exams.
Some people (including me) even wrote text editors and viewers with support to display a mix of text and picture for schematics, physics or chemical diagrams...
The US scene was also extremely helpful, with people such as JK Horn or Eric Rechlin.
Im 43 it guy and started playing with hp at 12, my own first « computer » with countless hours: playing, coding, debugging, reading txt files. Naturally when I bought my first intel computer at 19yo I installed freebsd, to later go to openbsd and Linux.
And the first thing I do on my android phone is to install hp48 emulator.
You may have heard of LZ4 or ZStd, the author is a French guy (currently employed by Facebook) who started hacking compressors on his HP48, this is how I met him a long time ago.
The software on this thing was pretty amazing, but surprisingly hacky in some ways. The RPL language had a system of embeddable objects in memory, but when the interpreter had to skip over an object (i.e all the time), there was no field marking its length, so it had to actually recurse through all the sub-objects to find the end.
IIRC there was the a hack where some memory locations could contain a direct pointer or a pointer to a pointer, and it would work either way because the same bits could be interpreted as a pointer or directly executed... or something of that sort.
https://www.amazon.com/2AP18AA-ABA-Prime-Graphing-Calculator...
but pretty good for the time.