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# Calculator blog

Musings and comments about our common interest

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## Next Step: the cable!!

It is no secret we are developing a cable for the now-standard HP calculator connector (which appears in the HP12c, HP15c and the HP10bII+ calculators)

It is difficult because it does not have a standard 2,54mm pitch - but we will find a solution. With it, we can foresee fixing any bugs that are in current firmwares (so far, nothing in the "main" firmware, but something in the NOMAS part)

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## Still more tests for overlays!

This HP16c overlay version has a little blurred yellow print - the jet seems to be too far from the surface. We'll receive it in a few days to try it mechanically - how it works. It can be used in any new Voyager calculator with the suitable firmware (HP12c -attention, NOT Platinum-, or HP15c CE)

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## More voyager overlay HP16c pictures - tests

Here is another picture fo the tests we are doing with overlays. difficult to get the process to get the colors right! Also the blue labels are still not well centered - next tests tomorrow! At least the keyboard works well and adheres well too: you need to shake hard the calculator to get it out. It will work well on that count!

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## Another speed comparison for the HP15c Collector's Edition

Let's try another speed comparison for the HP15c Collector's Edition, this time with a financial workhorse for financial duties: the HP12c (original version)

We will compare the time to calculate the interest rate in a long Time Value of Money calculation. The HP12c using its native TVM functions; the HP15c, using the Time Value of Money program in the Advanced Functions Manual (shifted to another place in the program memory - with so much memory I have entered several other programs too in lower memory positions)

The data for the problem:

• 360 periods (n)
• 480.000€ initial value (PV)
• -2050€ payments (PMT)
• 0 final/future value (FV)
• Solve for i

There is no general analytical solution for i : there is no alternative for iterative solving ! The HP12c uses an optimized machine-code algorithm, but it has a slow processor, dating from 1981 and running at 880 khz (give or take) - 38% faster than the HP41c. On the other hand, the HP15c is running a keystroke program, using labels and the HP15c's Solve function called from within the program, running the keystroked TVM formula in a loop.

The results:

The newest HP12c is faster than either - but has none of the other features of the HP15c.

So, having entered programs for %T, NPV/IRR (using solve too) and TPV, and despite how comfortable feel the incr%, T% and % of the HP12c, I will take just one calculator with me! Still a lot of memory to solve equation systems oe enter other programs. There is more concern about the label codes left than memory!