Personal Calculator Has Key to Solve Any Equation (1979) [pdf]

I used to wear HP t-shirts in the era of this article; "ENTER > =" and would earnestly argue about the wonders of RPN over algebraic notation. This is a wonderful glimpse at the algorithm that made that magical "Solve" button work. A couple of years ago I saw but neglected to save an article about how HP implemented all this in the chips of the day.

40+ years later I note that my day-to-day work either never uses the capabilities of an HP-34C or requires crunching more tabular data than a calculator can handle. While I still like RPN, I would not like to enter RPN expressions into the programming languages I do use. As great as it is in calculators, it is damn hard to revisit and figure out what I had intended let alone what someone else's code may have intended.

Damn shame what happened to the HP company and reputation in the intervening years.