[opencl]

It uses a pack of rechargable AAs, I have an HP-45 (the immediate successor, with the same battery pack) and replaced the original NiCD cells with NiMH. When I got it the batteries were clearly already a few decades old. AAs NiCDs were pretty common back then, I have an old TI and Soviet-made Electronika calculator that also use them.

[ghaff]

Right. It mostly wasn't a problem so long as you remembered to charge them before exams, etc. In college, I'd still bring a slide rule to final exams as backup just in case something happened although I never had a problem.

I started college just as scientific calculators were appearing on the scene. I had a TO for a couple of years because the HPs were still so expensive but I was able to pickup an HP-55 after a bit for a relatively affordable price (still probably talking about high 3 digits in today's dollars). That's what I used until I bought an HP-41CV when I went back to school and needed a more programmable calculator.