What's your favorite non-RPN HP?

[Dave Britten]

Perish the thought, I know. But in reality some of them were pretty decent. For example, the almost-programmable 17B and 19B. In a lot of cases, the solver makes it easier to create a "program" for relatively simple tasks.

Then there's the HP-2XS range, which I think were all strictly algebraic. The 20S and 21S are keystroke programmable, the 22S has a basic solver in it (I think), and the 27S appears to be a (non-programmable) hybrid of the 17B and 42S with at least some portion of the HP solver brought over. (Didn't they have to trim some of the functionality due to limited ROM space? Or am I thinking of something else?)

I'm partial to the 20S, personally. There's something rewarding about cramming a useful program into 100 steps and 10 registers, relying on undocumented quirks of INPUT and SWAP to do so. Plus it's just a quick, well built, nice looking machine.