Not sure what happened to all my old stuff. But you can still find a $4 Casio basic calculator for doing simple calculations. I never figured out HP's RPN so I never got one.
A relative gifted one of the Sharp computers that could program basic, but I only used it as a calculator. First time I'd ever operated anything using a CR2032 battery, which were expensive back then. I remember as the batteries wore down, the contrast of the LCD would go down, but there was a dial to boost it, albeit at the expense of draining the battery faster. The thing I remember it did that used the most electricity was to compute factorials. I think it did it via brute force rather than using lookup tables. I would enter something like 67! and I could actually hear it buzzing as it did the calculation. I think that was the biggest value because any more and it would overflow, but only after trying.
I knew someone who had an ancient early 70s TI calculator. It only operated off a power adapter (might have been possible to rig batteries to the connector) and had digits via 11-segment red LED display.