hp 12c platinum
what about calculations
new to the 12cp is the ability to operate by algebraic entry (alg) as well as in rpn. the alg/rpn option is common to hp financial models and was also available on the hp17bii. the hp10b however was alg only whilst the original 12c was rpn only. the ability to choose is clearly the best of both worlds. the only noteworthy point of alg entry is that there is no operator precedence. so, for example, 2+3*5= calculates as (2+3)*5 = 25.
the 12cp covers the following general features: percentages, calendar date arithmetic, simple interest, compound interest, nominal and effective rate conversion, time value of money (tvm) with amortization and optional odd-periods. discounted cash flow analysis (npv and irr), bond price and yield (30/360 as well as actual), depreciation, 2d stats with linear regression, logs and usual calculator operations.
the unit is also programmable with 308 lines (steps) by default, which can be increased or decreased by partitioning memories. note: early versions of the 12cp have a bug preventing more than 253 steps being used properly.
for more information about the feature set, the 12cp manual can be downloaded from hp in pdf format.
lets try a tvm example
run of the mill tvm calculations should be just fine. lets try some slightly more tricky cases and see what we get.
for this, we have, PV=0, PMT= -0.01, n = 365*24*60*60 and i = 10%/n. enter these as
which is agrees with the 12c and is the correct answer (unlike the 10b). however, the opposite problem of determining i (the interest rate) from the other variables gives the 12cp a hard time. after performing the above calculation. enter, 0 i, to clear i, then press i again. this will attempt to solve for i (which we know) from the other variables and the newly computed value of FV.
unfortunately, the machine goes off "running" for 4 and 1/2 minutes (which is far too long). it appears in trouble converging to a solution, but has no internal mechanism to improve this. the original 12c, however, copes with this case easily and readily returns the correct answer. at least the eventual result from the 12cp is the correct one.
lets try another
for the 12c,
it goes as follows;
whilst the 12cp gives 3.125001600e-6% which is more accurate than the 12c. well done.
as a final tvm test for solving i, consider the unrealistic example of n=360, PMT= -10, PV = 100 and FV= 0 to solve for i. this is unrealistic because as you can see, a rate of i = 10% would never reach fv=0 and a value somewhat less than 10% would reach fv=0 in much less time than n=360. so we know that the value for i here is very close to 10% but not quite.
the actual answer is, i = 9.9999999999999874503000321496% which can only be shown in 10 digits as 10% exactly which can be seen to be the wrong answer. so what is a calculator to do?
the 12c gives 10% as the solution, which is correct insofar as it can display. this is interesting because it wont have converged to this result iteratively, but instead bailed out as best it can.
the 12cp, on the other hand, tries to iterate and fails to return a result. the purpose of this example is to show that there some borderline cases that cause the 12cp to fail to reach an answer. it would have been better, in these cases, to either detect and bail out (like the 12c) or return an error condition rather than continue running indefinitely.