This is timely.
I recently found my first and second calculator in an old drawer. I had no reason the think either would work, but I put fresh batteries in both — two AAs in the Casio and four button cells in the Sharp — and they still work.
The oldest (a
Casio CP-801C) was a Christmas gift I got when in Grade 5 and dates to 1975, give or take. The cool-ass blue-green fluorescent numbers still light up just fine.
The second calculator (a
Sharp CT-550), which is also a clock, day-date thingy and stopwatch, was a combo birthday and Christmas gift from the
entire family a year later. I seem to recall its being around $50 then, so a bazillion dollars in today's money. I wanted it so badly because it flipped open like a communicator and would beep when the stopwatch hit zero in countdown mode.
To round it out is an
HP-42S, a programmable RPN calculator that got me through a couple of science degrees.
It will let you know if you've created a black hole and it can work with complex numbers, which
is kinda neat. It also has a guzinta button -- e.g., 3 guzinta 12 four times.
Joe