I recently purchased a Privileg 892NC calculator at a garage sale. It is a financial calculator which seems to be very similar to the Commodore F4146R. The keyboards are identical but the 892C is about an inch longer.

I am working my way through the capabilities of the 892C. Page 35 of the manual presents the solution to an elementary interest problem; i.e., for n = 3, I = 7% and a present value of 1000 what will be the future value? The solution sequence is given as

C 1000 PV 7 I 3 N CMP FV

where C is a clear key and CMP is a compute key which acts similarly to the CPT key on the TI-MBA and TI-BA-55. The answer is given as 1255.043 . The demonstration continues with the sequence

- DIS PV =

where the DIS PV sequence recalls the inputted present value of 1000 and the subtraction then yields the accumulated interest of 255.043 . All well and good up to that point, but for some reason I decided to see what would happen if instead of the - DIS PV = sequence I used - DIS I = . To my surprise the machine refuses to do that calculation. It will also refuse to perform in response to the - DIS N = sequence. It seems that the programmer recognized that the dimensional inconsistency was such that the calculation shoudn't be allowed. That's an idea that warms the heart of this old aero engineer.

The machine will accept a numneric keyboard entry after the minus sign. Apparently, the programmer made the reasonable assumption that if the user made an entry from the numeric keyboard then the user prbably know what he was doing.

There are several other Commodore and Privileg financial calculators. I don't have any of them in my collection so I can't say whether or not they impose dimensional consistency.

Calculators in my collection which permit the user to recall the contents of the financial registers but which do NOT impose a check on dimensional consistency include the TI-MBA, the TI-BA-55, the HP-10B, the HP-12C, the HP-17B-II, the HP-38C and the Sharp EL-733A.

Does anyone know if there are other financial calculators which impose dimensional consistency?

Palmer