
Look for Parens calculator online and you will find the old HTM manual. This is the calculator used in Treos and Visors.
Extract:
"TVM (TimeValue of Money)
TVM is the standard financial jargon acronym for TimeValue of Money, and is used for computing the effects of compound interest in loans, savings accounts, mortgages, pension funds, annuities, etc. To use the TVM function, you must set the values of 4 out of the 5 TVM variables: PV (present value), FV (future value), Pmt (payment per period), APR (annual percentage rate of interest), and N (number of payments). The number of payment periods per year must be set in the P/Yr variable. Once you've entered these values, you can tell Parens to solve for the remaining variable. To set a value for a variable, enter the number and tap the appropriate variable key. To solve for a variable once the others have been entered, tap the Graffiti area once to put the PalmPilot into Punctuation Shift mode (a big dot will appear in the upper left part of the display) and then tap the variable key to solve. Once you've entered and/or solved for all the variables, you can easily play around with different loan parameters by changing one or more values and then resolving.
For example, to compute the payment required for a loan of $1000 dollars at 7% annual interest paid in 12 monthly payments, enter 1000[PV] 0[FV] 7[APR] 12[N] 12[P/Yr], tap for Punctuation Shift mode, [Pmt]. The result is 86.53. Negative numbers indicate payments you make, while positive numbers indicate money you receive. Now to see how much the same loan would cost if repaid over 18 months, just enter 18[N] dotshift[Pmt] to see the result of 58.68.
You can also recall the current value of a variable without solving for it by drawing a slash from the upper left to the lower right corners of the Graffiti alpha area to put the PalmPilot into Extended Shift mode (a slash will appear in the display) before tapping the variable key to recall. Finally, you can tap the Edit key to bring up a text display of all the TVM variables at one time, where you can edit them using Graffiti instead of using the calculator keypad. You can solve for a variable in this display by erasing the value in one of the number fields and then tapping the Solve button. There's also an option on this page to select "Begin" or "End" mode for all TVM calculations. Normal loans are computed in "End" mode, meaning that a payment is made at the end of each payment period. Some kinds of annuities and other strange beasts are paid in "Begin" mode, where a payment is made at the beginning of each payment period; this selection allows Parens to swing both ways.
Once you've filled in and solved all the TVM variables, you can tap the Amrt (amortization) key to display a nifty amortization schedule showing how much of each payment will go towards paying off the loan (principal), how much will go towards interest, and what the remaining balance will be after each payment. Check the box at the bottom to see how much total principal and interest will have been paid so far after each payment. Note: Parens uses a fullprecision idealized computation for the amortization schedule, rather than rounding the payments to whole cents. The listed values may vary by a few cents from a given loan's actual payment schedule over time, due to the various ways that different lenders handle rounding the amounts. Also, due to the extremely tight space requirements on this display, Parens will always display this list in Fixed(2) format regardless of your main display settings. I recommend that users who work in Lire, Yen, or other "integer" currencies divide their monetary input variables by 100 to cram as many digits as possible into the display."


