PPC Journal V2N6 - TVM i% unknown on HP-65

[Dieter]

(10-17-2015 01:56 PM)SlideRule Wrote:  see attached
(...)
hope I'm typo free

Ah, my experimental program. ;-)

There is an error in the keycode of the y^x command. But, more important, the remark between step 4 and 5 in the user instructions was taken from the original PPC version, while my program uses the same sign convention as later HPs, i.e. PV, PMT and FV may be positive or negative. That's why there is a minus instead of a plus in the initial guess calculation.

Sure, all the stuff starting at LBL A can be removed if the input values are stored directly in R1...R5. The idea was – like in the original program – that the keys of the second annuity program (the one that solves for the other variables) are mirrored so that the user only has to load another card while the A...E keys do the same as before. If this part is removed the code can be improved in several ways. For instance the program may exit if the initial guess is exactly zero (in this case that's the exact solution), or the program may check the relative instead of the absolute error after each iteration.

Dieter