## Guido's RPN calculators |

The algebraic notation as used by most calculators LOOKS simpler. Telling a student "Just type it in as you find it in the textbook" is easier than explaining how RPN works. Have however a look at this interessting experiment that compares calculators with RPN and algebraic notation.

The gsrpn calculator |

I have been using HP RPN calculators since the beginning of my university years. Now that PCs and Laptops are one every office table I have been looking for a good calculator that just runs independent of the operating system on any computer out there. I did not find one so I wrote one my self. Beginning of 1997 I started to write rpnjcalc. I have used it once in a while but it never really felt like a real HP pocket calculator. I always found my self looking for a real HP pocket calculator when I had to do some calculations. So finally in March 2008 I decided that it must be possible to write a more usable calculator in Javascript and I developed gsrpn

Later I discovered that Greg Hewgill has written a very authentic version of HP 15c which is available at http://hp15c.com/ [Local copy]. He did a very good job. If you prefer to install a hp15c on your PC then try http://hp-15c.homepage.t-online.de.

It's interessting that this calculator is "1 * π inch" high and "Φ * π inch" wide (where Φ=1.61803...=(1+sqrt(5))/2 prounouce: phi, Φ is also known as the "golden ratio", π=3.141... prounouce: pi, Φ*π=5.083).

For several month a petition was circulating on the internet to bring back the 15c and it seems HP took notice and produced end of 2011 a "15c Limited Edition", the HP15c-LE. It does not only look similar to the original it is very much like the original with some small differences. On the down side are a number of firmware faults: hpmuseum.org, list of 15c LE bugs but on the up side is the advantage that the 15c-LE runs faster than the original 15c and it has the same good quality keyboard with an excellent "click".

The list of faults of the HP15c-LE might look long list but the only real problem is the fact that the PSE (pause) function can only be called once per program execution. The non working low battery indicator is pretty bad too but you can just use a voltmeter and test the batteries once in a while as described in my hp15c-le battery test article. There is no need to take the batteries out for testing.

All programs that I have ever written are however not affected by that PSE bug.

It's a bit unfortunate that the HP company of today is not any more the company that took pride in producing high quality measurement equipment and calculators. They have not provided a firmware update until a year later and I don't think they will.

I have investigated the HP15c-le power and battery problems and written about them at http://tuxgraphics.org/npa/hp15c-le-power-test/

www.swissmicros.com (previously known as www.rpn-calc.ch) produces a hp15c compatible calculator. It's emulating the original Voyager processor on new hardware and runs runs original HP15c firmware. The hardware is designed with firmware updates in mind. It has therefore as opposed to the HP15c-LE no software bugs. I like the fact that the color scheme follows the original hp15c. The keyboard could however be improved further. The pouch is made from real leather.

The DM-15 HP clone

- convert a floating point number into a fraction (numerator and denominator)
- quadratic equation solver, x
^{2}+p*x+q=0 - number conversion dec->binary
- Euclidean algorithm, Greatest Common Divisor (GCD)
- A dice
- Generic unit conversion

I have long been looking for a good replacement pouch for the 15c. Especially the HP15c-LE pouch is too hard and too sturdy my old one is on the other hand wearing out and getting too loose. After trying several options I made some pouches out of neoprene and they are really good. If you want one, you can order them here: http://shop.tuxgraphics.org/fan/hp15c-hp12c-pouch.html.

The HP12c has no trigonometric functions but you could use the following approximations if you ever need those functions.

- linuxfocus.org RPN calculator article
- gsrpn -- a HP alike RPN calculator
- http://www.hp-collection.org/
- http://hp15c.com/, online simulator
- http://www.hp42s.com/, everything hp42s
- http://hp-15c.homepage.t-online.de, a hp15c simulator for Windows, Linux and Mac OS X
- http://www.hpmuseum.org/
- http://www.hp.com/calculators/, HP produces again some of the classic RPN calculators.
- http://www.hpcc.org/calculators/hp15.html

© Guido Socher