HP41 Mcode Entrypoint for 'high precision numbers'

[PeterP]

Hi,

In PPCJ-V10-N7 Charles Bouldin talks about the normal arithmetic entrypoints ADD2_10 etc. In his first paragraph he also says "... additional entry points for high precision numbers which occupy a pair of addresses exist but will not be discussed here".

Does anyone else know about this entry-points and how to use them?

Thanks!

Cheers

Peter

[Eric Smith]

Addresses (hexadecimal):

ad2-10   1807

ad1-10   1809

ad2-13   180c

mp2-10   184d

mp1-10   184f

mp2-13   1852

dv2-10   1898

dv1-10   189a

dv2-13   189d

Comments from the source code:

******************************************************

*      common math entries                         ***

*          if number is 2-10,                      ***

*             then form is:                        ***

*                A has 10 digit form               ***

*                C has 10 digit form               ***

*          if number is 1-10,                      ***

*             then form is:                        ***

*                A has sign and exp                ***

*                B has 13 digit mantissa           ***

*                C has 10 digit form               ***

*          if number is 2-13,                      ***

*             then form is:                        ***

*                A and B as in 1-10                ***

*                M has sign and exp                ***

*                C has 13 digit mantissa           ***

*                                                  ***

*      on exit, C has 10 digit form                ***

*               A and B have 13 digit form         ***

*                                                  ***

******************************************************

[PeterP]

Thanks Eric! Now I just have to figure out how to use them :-)

Cheers

Peter
PS: it would appear that they are not double precision but just 13 digits instead of 10, correct?

[Eric Smith]

Yes, 13-digit mantissa. The intent was that they provide more precision for intermediate results in calculations of the elementary functions (trig, logs, exponentials, etc). The extra 3 digits makes a big difference, though it isn't sufficient to guarantee correct rounding for all cases.