HP-12C undocumented registers

[iMatt04bit]

Hello,

I am writing a Java HP-12C calculator sim, mostly because I wanted a fun exercise for learning Java, and because I really like HP calculators.

I have read the 12c manual and implemented the equivalent of registers in code, and these are working well. But I have the feeling that there may be some registers used during financial computations that are not described in the manual.

I am working on the TVM functions which are producing good precision as tested against other sims and by linear spreadsheet analysis.

If anyone has further insight they could offer on the inner workings it would be much appreciated, thanks,

Matt