I have two of these - one for the workshop/shed and one for general use. I try to keep them programmed with the same functions mostly.

The HP35s is a useful RPN programmable scientific calculator, with a few annoyances, but I'm glad I've got a couple lying around to play with. Of course it's not possible to interface a computer with the HP35s, so I have no electronic records of my programs. I write everything down in a notebook, in case I need to re-enter it later, but sharing it online isn't quite as straightforward as with the SwissMicros calculators.

• See HP35s Progs