"DoN. Nichols" wrote in message
...
In article ,
Erik wrote:

Hmm ... I *think* that the 'C' in the model number indicates
that it is one of the early ones based on CMOS technology, instead of
the NMOS used in the earlier ones -- 35, 45, 55, 65, 67, etc. I
believe
that there was a 25C as well, a smaller version of the form factor of
the 35 et all, but with CMOS technology.

[ ... ]

I wouldn't bet my life on it, but I recall reading that the 'C' in all
those HP calculator model numbers meant they had continuous memory...
something really cuting edge at the time. I think the 25-C might have
been the first with it.

You might well be right about that -- but at least the memory
had to be CMOS to not drain the batteries over time, and mine still run
several years on a single set of three 357s.

Maybe I should hook it up to a power supply, and measure the
current drain when "on" and "off", just to see.

Enjoy,
DoN.

The '25 from 10' away looked like a mini version of the original '35 but the
'25 was a full-bore programmable calculator, registers, conditional
branching, could do some pretty neat things with it.

The '25C was the '25 with a battery backed-up CMOS for the program storage.
Both had red-LED displays and both ran on a pair of AA NiCd's.

The '15C and later 'C's by were LCD display and ran on watch batteries (i.e.
357).

The LED display calculators gave the impression of speed because the
displays flashed while they worked. The LCD models I recall seemed slow at
first because the display just blanked until it was done doing whatever.
They also took longer to respond to each key entry, maybe that was it.

I change the batteries in my '25 every 5 years or so. For whatever reason,
familiarity, I don't know, I have a bunch of the later LCD models but still
like the '25 best, and use it the most. That being a relative term, as
almost anything I don't crunch in my head is better off being done in a
spreadsheet.

Great tools. And they are all great around metal!

Bob