dm319

The official Swissmicros 2-line firmware dropped on the Winter Solstice as an early Christmas present. It also has a nice set of constants and conversions.

I'd been toying with the idea of what RPN calculator a kid could use at school here in the UK. I thought the sticking point would be that most RPNs are programmable, but turns out that isn't an explicit exclusion on the JCQ calculator guidance for GCSE and A-level exams. They can also use graphic calculators. There is a hard no on CAS. The HP-15c seemed the least likely to cause issues with invigilators, so went for this. We'll have to see if it works out though.

The HP-65 was not only HP's first programmable scientific, but it could also read and write magnetic cards. There were several 'pac's of cards allowing it to tackle financial, astronomical, aviation, electrical and other speciality field calculations. The buttons were double shot and have a lovely tactile click. The red LED screen is remarkably crisp and easy to read.

These are the tests which can give you quite a good profile and accuracy rating for your financial calculator. Any more contributions and confirmation are very much appreciated and I will update the swissmicros page (though I may need to move it off there at some point).

| #  | Ref        | N            | I%YR      | PV       | PMT          | FV        | P/YR | Mode  |
|----|------------|--------------|-----------|----------|--------------|-----------|------|-------|
| 1  | DM         | 38 x 12      | 5.25%     | 270'000  | ?            | 0         | 12   | end   |
| 1b | DM         | 38 x 12      | ?         | 270'000  | -14'584/12   | 0         | 12   | end   |
| 2  | SlideRule  | 360          | 15% → 12% | 100'000  | ?-?          | 0         | 12   | end   |
| 3  | Kahan 1983 | 60x60x24x365 | 10%       | 0        | -0.01        | ?         | =N   | end   |
| 4  | DM         | 480          | 0 → ?     | 100'000  | ?→ PMT       | 0         | 12   | end   |
| 5  | Dieter     | 10           | ?         | 50       | -30          | 400       | 1    | end   |
| 6  | Dieter     | 10           | ?         | 50       | -30          | 80        | 1    | end   |
| 7  | A Chan     | 10           | ?         | -100     | 10           | 1e-10     | 12   | end   |
| 8  | Miguel     | 32           | ?         | -999'999 | 0            | 1e6       | 1    | end   |
| 9  | DM         | ?            | 25        | 100000   | -2083.333334 | 0         | 12   | end   |
| 10 | DM         | ?            | 25        | 100000   | -2040.816327 | 0         | 12   | begin |
| 11 | robve      | 60x24x365    | 1/6% → ?  | 0        | -0.01        | ?→ FV     | =N   | end   |
| 12 | robve      | 40           | ? → I%YR  | 900      | -400         | -1000 → ? | 1    | begin |

2: https://www.hpmuseum.org/forum/thread-20707.html
3: https://www.hpmuseum.org/forum/thread-1012.html
5, 6: https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv021.cgi?read=234439
7: https://www.hpmuseum.org/forum/thread-18359-post-161549.html#pid161549
8: https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv017.cgi?read=120592
11, 12: https://www.hpmuseum.org/forum/thread-16565-page-2.html

Puzzle 2 is from here, and needs you to calculate PMT given n = 360, I%YR = 15%, PV = 100'000, FV = 0, then calculate PMT, but with I%YR = 12%. Subtract the two results, and put that back into PMT, then change n = 36 and I%YR = 15% again, and calculate PV.

Puzzle 3: you may need to divide I%PY by N depending on how your calculator handles i vs I%YR and what the limit is on P/YR.

Puzzle 4 needs you to calculate PMT first given I%YR = 0, then re-input this back into PMT and calculate I%YR. On the HP-12c this is best done by pressing x<>y twice before putting back into PMT.

Puzzle 11: calculate for FV first, re-input back to FV and compute I%YR.

Puzzle 12: calculate for i first, re-input back into i and compute FV.

The other puzzles are just a solve for '?'.

They can be a bit confusing, so I also did a couple of videos here and here solving them on a DM-42 and HP-12c.

RPN83P running on the TI-83 Plus

A random shot of my calculator 5000 miles from home while I enjoy a beer near the Pacific. We had been discussing how much water was on earth and what size of a ball it would make. I have no affiliation with the brewing company so apologies for the product placement.

HP's most accurate financial calculator, oddly enough, and despite only returning the ceiling of solve-for-n.

First post on Lemmy, and i see you like pens too :)