The calculators I eventually settled on in college and grad school were HP's RPL line, the 28S and the 48SX (the latter got stolen--it was too expensive to leave lying around). There were several later models. Eventually HP open-sourced the firmware for them, so a lot of free mobile emulators exist--and these were the most powerful calculators they ever released, though RPL subtly changed the way HP's RPN calculation worked in ways that were not to everyone's taste.
But RPL was a great programming language, sort of a strange cross between LISP and FORTH--it gave the stack unlimited depth and allowed putting everything from graphical objects to programs on it, instead of just numbers. In some ways it was a functional programming language. These calculators also introduced some CAS capability: they could do symbolic algebra and calculus to a limited degree, though it was a bit cumbersome compared to what you could get for a computer.
These days, I don't use all of those capabilities on a regular basis, but a 48GX emulator is my go-to calculator.
Those are all much later models than the ones you're looking at, from the late 1980s and early 1990s, with multi-line LCDs and graphing capability.
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But RPL was a great programming language, sort of a strange cross between LISP and FORTH--it gave the stack unlimited depth and allowed putting everything from graphical objects to programs on it, instead of just numbers. In some ways it was a functional programming language. These calculators also introduced some CAS capability: they could do symbolic algebra and calculus to a limited degree, though it was a bit cumbersome compared to what you could get for a computer.
These days, I don't use all of those capabilities on a regular basis, but a 48GX emulator is my go-to calculator.
Those are all much later models than the ones you're looking at, from the late 1980s and early 1990s, with multi-line LCDs and graphing capability.