Reverse Polish Calculators
Standalone calculators are rapidly disappearing and becoming collector’s items. I still use mine quite often in spite of an ever present computer with far more capability.
The first electronic calculator that I used was an HP9810 back around 1975. This was a beautiful piece of equipment, very well made, readable and usable buttons with great tactile feel. And it was used reverse polish notation, i.e. you put in two numbers then added or whatever. I thought this was great since you could pretty much start anywhere in a fairly complex equation and solve it without resorting to storing values in memory and without planning ahead how you were going to go about solving it. Later used an HP 9845 graphical desktop computer as well. Kind of like a really fancy calculator.
Later, at the same company, they bought the first HP handheld calculator the HP35. As with the desktop calculator the keys had great tactile feedback and I really liked the reverse polish format.
Later when I bought my own calculator I first bought and HP21, then was given an HP11C and then thought I had lost it (found again a year later) and bought an HP42S. I still use the 11C and 42S today even though they are pretty much collector’s items. I hope they’re replaceable if they should finally die. And really wish that HP still had a calculator division. Now I do also have quite a large number of slide rules but I really don’t use them any more. Hmm, if batteries become an issue… just maybe…