HP calculators and decimal (BCD) floating-point precision...

[sur-behoffski <sur_behoffski@...>]

(Replying directly to the list; sorry, as usual, for breaking any
relevant threads.)

In the distant past, I owned, and loved to use it for many years,
a HP-29C with *CONTINUOUS MEMORY!!!!*  Also, it had 98 steps for
programming algorithms.

IIRC (but the Web is not backing me up here), there was a second
"Applications Book" of useful problem and elegant algorithms for
solutions... authored by William Kahan.

Anyway, to get to the point of HP calculators and the present
precision discussion:

My recollection is that all computation internally for the
built-in algorithms was performed in ** 13-digit ** registers,
and the final result was rounded to ten digits for display.

I don't know if the internal storage registers were limited to
10 digits, or if they also supported 13-digit floating-point
values.  This would have been relevant where user-defined
programs (and subroutines etc) were executed.

My recollection may be incorrect... but if not, it may explain
some of the results that people have been talking about.

cheers,

sur-behoffski etc etc