HP41: accuracy of 13-digit routines

[Ángel Martin]

(09-02-2015 10:18 AM)Dieter Wrote:  Thank you very much. So the 13-digit routines truncate after 13 digits. I assume this also applies to the transcendental functions (log, exp, trig etc.). Now if I set a WP34s to RM 4 (truncate) and apply a RSD 13 to every result, this should yield the same result as the 41's 13-digit routines?

Typically that seems to be the case: the 13-digit result is held in the {A,B} registers, with the 13-digit mantissa in B<12:0> and the sign and exponent in A. Once the math routine is done it transfers the mantissa from B to the C register, most usually using the instruction C=B M - thus it is a 10-digit version made by direct truncation.

I however have done some rounding *prior* to this truncation in some of my own math functions - hard to remember which ones though...

Cheers,
ÁM