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HP41 Mcode Entrypoint for 'high precision numbers'
Message #1 Posted by PeterP on 29 July 2008, 12:53 p.m.

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

      
Re: HP41 Mcode Entrypoint for 'high precision numbers'
Message #2 Posted by Eric Smith on 29 July 2008, 5:28 p.m.,
in response to message #1 by PeterP

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         ***
*                                                  ***
******************************************************
            
Re: HP41 Mcode Entrypoint for 'high precision numbers'
Message #3 Posted by PeterP on 30 July 2008, 1:37 p.m.,
in response to message #2 by Eric Smith

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?

                  
Re: HP41 Mcode Entrypoint for 'high precision numbers'
Message #4 Posted by Eric Smith on 30 July 2008, 2:37 p.m.,
in response to message #3 by PeterP

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.

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