It's obsolete now, but it's the best calculator design in the history of calculator designs. I wish there was a modern version. The old ones are starting to break down, and many cost more today than they did new. Many common operations are very, very slow relative to modern models.
The TI calculators are horrible in comparison, and the HP Prime is a blunt kludge.
Key features I'd like:
- High-quality keys
- RPN
- Being able to handle units. Can't tell you how many times that's saved me from metaphorically blowing up a space shuttle.
- Very rapid use of variables. `<< 1/ SWAP 1/ + 1/ >> P A R STO` and 11 keystrokes later, I have a function defined for parallel resistors.
- Comprehensive equation libraries
- Ideally, some level of backwards-compatibility (even through an emulator kludge)
Key modernizations:
- A fast CPU
- A high-resolution color touch screen, with nice rendering of symbolic equations
- A more modern engine for symbolic manipulation
- Python (integrated with RPL, for the numeric libraries)
- Modern connectivity (802.11+USB-C+bluetooth, supporting data streaming, external keyboards / mice, acting as a keyboard / mouse, streaming to an external screen, etc)
- Open-source, and software packages (apt-get style, ideally, and app store style, possibly)
One thing I've considered doing -- if I ever had time -- was to make an HP48 keyboard for my desktop. I don't need the portability, and I wouldn't even mind if the software were running on my desktop.