Musings and comments about our common interest
Back at their heyday, there were those that bought the HP 41c because it was the ultimate calculator, only to discover that the cheaper HP 15c had many more functions, and more conveniently located in the keyboard. Some things that the plain HP 41c did not have:
-extended factorial (gamma function)
The user of the hp41c could lie to himself “I can have all that if I buy the right modules”, but that would be an enormous money outlay. It must be said that the advantage module provided most of that missing functionality, but it was never as well integrated as it was on the 15c.
both competitors face to face. Forgive the picture quality!
For example, the complete 4-level complex stack in the 15c; or how well integrated were the matrix functions and the “user” mode to automatically change the pointer for matrix data entry; or the clever use of the permutations and combinations keys for matrix transformations. It really was a clever and elegant device, and still is: more than 25.000 units of the new version have been sold since September 2011.
The only two things where the hp41c always got the upper hand was in alpha capabilities and connectivity. (In fact, it can be argued that it has never been bettered in that area, the USB connection of the 50g family being a poor shadow of the many modules and printers that the HP 41c could drive).
30 years later, the HP 41c user got vindicated - finally. With the “CL” module, you have access to all the functions ever created for the HP 41c in the different modules - all at the same time.
My preferred current set-up (that is good for my work and my hobbies at the same time) is Advantage pack, Sandmath module (latest version) and HP 41Z module (the Z module has a much better complex support than the advantage pac, in my humble opinion - thanks Angel Martín!). With it, I can say I have let the HP15c behind. But it has taken ages and effort!
Many people, when they see me using a calculator in my job, argue about why using now a calculator, when there are so much more powerful alternatives. They always try to convince me about how much better is a spreadsheet, etc.
Let me try to organize my thoughts about what's the point of having a calculator nowadays, when we have computers and, let's not forget, smartphones. If you are reading this, chances are you are as nut about calculators as myself, and you are as well faced with those questions from time to time. I hope then I can give you some elements for discussion. I would like to ask you to post your own reflections, to reinforce my arguments as well.
(Other times I get challenged about collecting calculators, but for that, to be honest, I haven’t found any good argument in our defense!!)
In order to systematize the discussion, let’s see first which are the most likely alternatives to your calculator (the most likely, not all of them. Remember the HP-01? Or more typically, the Casio watch calculators?)
In this post I will deal with the first ones, leaving the others for a further post
PC running spreadsheets
On one side, it is true that an spreadsheet carries you further and with less effort - and it leaves a trace of what you are doing. You don’t need to write with your pencil the intermediate results.
Today spreadsheets have very powerful instruction sets. And it is very likely that what I now think that can't be done with spreadsheets, is more due to my lack of knowledge of the tool than actual lack of that feature. I am now thinking of all matrices-related things.
PC running a mathematical software (like Mathematica)
I have to be honest with you – the last time I used one of these, I was still using MSDOS, when I was studying engineering in the 80’s. For me, this option is limited to Academia – which is the environment that would buy and maintain this kind of software. I have to confess that my opinions on this area are based on very out-dated information, and I cannot add value. (here is where you, reader, can join in!)
Before the IBM PC was born, there was a Personal Computer produced by HP – the HP85. It was a fantastic machine, running a BASIC-oriented operating system, with a big number of mathematical operations for the time, and that could be programmed for any kind of mathematical challenge. In this case, some of you could tell me that it was not an alternative to calculators: it was, in fact, a calculator (its CPU was based on calculator CPUs, at a time where 6502, 8080 and Z80 microprocessors were common on other machines)
There were ROMs that enhanced its capabilities in areas that are the realm of calculators: matrices, etc.
PC running a calculator program
I am running in my Mac a couple of different HP15c, a HP42s, a HP41cx, and under the Windows screen in parallels, a HP50g. Even the most advanced scientific calculator (the wp34s), started its life based on the SDK of the 20b - if I am not mistaken. I have written a blog article for the humble Mac OSX calculator, that can be configured as RPN as well.
The choice would be even bigger, were I running Windows as main machine. I have not explored the options for Linux. I might be interested if I still was in the Windows camp, but I moved to Mac and I’m not thinking about changing again.
The discussion of the many working alternatives for calculator programs is well beyond the scope of a single post, and deserves an article or a series of articles from somebody much more knowledgeable than yours truly. Let’s focus instead on the advantages and disadvantages:
There are times when you can’t use a computer – meetings!
There are two kind of meetings in my company: with and without computers. When you see a meeting where everyone is using a computer, you can assert than more than 50% of the attendees are not really there, but emailing or finishing their presentations for their turn. Therefore, they are not listening to what whoever is speaking has to say.
More and more, some managers are insisting that laptops are closed while the meeting takes place – at least, while they are speaking! Therefore, the calculator is your only alternative to number crunching during a meeting.
As well, in a meeting you need to give a fast answer, and this would be difficult with a computer. With a calculator you can do fast and dirty calculations; with a computer, you lose and inordinate amount of time formatting even the most minute calculation. There is a brain switch that allows you to take approximations and shortcuts with a calculator, but impedes all but a perfect mathematical model when you try to do the same thing with Excel!
As conclusion of part one: it is not clear at all that a computer can take all the work a calculator does. Let’s see in part two what happens with the other devices mentioned at the beginning of the article.
If you remember, some time ago we reviewed a project for a clone HP15c calculator made in Switzerland. While the project was extremely interesting, it had the worst possible timing: it coincided with the reissue of the HP15c by Hewlett Packard. With good sense, the creators backed off and re-thought the project, in order to give the user something more than the original did.
I am carrying the HP15c Limited Edition every day with me, and while its size is smaller than most calculators, it is a tight fit in my shirt's pocket, and it fits well in my jacket's; but sometimes I would like it to be smaller.
Enter the HP15cc:
First a pre-production sample
Then a more developed sample:
I look forward to get one. and you?
We have a page about RPN: why it is a better way to use a calculator. So far it is embryonic - we need to go much further in the description. We need to have something simple enough to send to one of our friends, and attractive enough so that he gets interested in it.
I wanted to include an applet of an RPN calculator, but I have problems in storing files in this server - since is not mine. So far I have not been able to include a proper Java RPN calculator - yet.
What I have found is a nice site with emulators in several environments/operating systems - one of them as Java.
You will see that is a nice example. You can start practising with it...you'll probably want to hone your skills with it...just in case...
By the way: it is a very good tool for RPN training. Just make sure to open the window as big as you can: on the right side you will see the stack and the registers, and see the effect of what you're doing on the processor.
Of course: no liabilities accepted if the machine is not a perfect replica of HP 15c. I have not tried to program it, and just tried some examples with complex data; but did not do a full review of it.
Today I came across a very interesting project: The Kinome Voyager
It consists in a calculator of the Voyager series enhanced with hardware and memory that allows it to run the firmware of the different Voyager calculators. You can select, with a special switch on procedure, which one will you use. In the video below, you can see the user selecting between 15c and 16c.
Please click on the "cc" symbol on the lower right to get access to text subtitles that illustrate what the user is doing.
An interesting feature is that each "environment" keeps its memory even when running a different calculator model.
For more information, please read the following link in hpmuseum.org:
Read from message 33 onwards - the rest makes reference to this summer "#calculatortrendingtopic"...
If it is ever available, I will buy for sure one...I have enough calculator "donors" for frankencalc surgery...
I have read in the internet about a new venture whose aim is to reissue a HP15c clone. You can find about it here:
They show as well some renderings of how the machine would look like:
And you can see that they have been able to produce a working prototype:
There are some informations about price - around 69 CHF. Having lived in Switzerland myself, I can attest that it is not the cheapest country around by a long shot, and still this is a very good price.
There are several considerations when you think about it:
Finally, I include date calculations. The one I use more is the HP12c's DDAYS operation. I then set to find in the web software for it. I did not find it for the 15c, but I did for the 42s, that I then adapted. Attention - it has been modified to cater for European date format: dd.mmyyyy - you will have to go to the part where it decomposes the number into the parts and then change a few lines there.
The strategy is just to convert the date format to Julian number, convert the other date, and subtract. Fortunately, the DtoJ subroutine does not consume all 4 stack registers - or we would not be able to subtract them!
Once entered, you will still have 16 registers left. (we assume that we have set 11 registers for program use: from register 0 to .1 (so that you can enter the investment + 10 years + the number of years for the IRR program seen in past article). These 16 free registers allow you to invert a 4x4 matrix, or to solve 2 equation systems with the same coefficient matrix (a typical thing when you're solving structure problems - you apply the same set of linear equations to different conditions)
Here it is (and I have finished with it. The only possible addition would be the DATE+ function. The D->J is a part of the DDAYS program; We would just need to create the J->D - at the expense of losing necessary registers!)
The NPV and IRR are other favourites. There is another program in the Advanced Functions Handbook, that allows for up to 24 groups of cashflows (assuming you do not have any other program in memory!) and using 68 steps. However, as I said before, in my company we limit Capital Expenditure Proposal analysis to 10 years, so that I set to make a shorter program for 10 cashflows.
Register 0 is for the initial investment. Register ,1 contains the number of years to calculate (good to limit the loop and increase speed). Registers 1 to ,0 contain the flows of each year.
The system takes X as discount rate (in %). It can be then used to find the IRR through the Solve feature, entering a bracket of guesses in X and Y.
Now we come to a weighted average calculator. In many occasions I need to get the average margin of all the brands we sell.
But the weighting in HP12c works inverse as I would do. It calculates the average of Y weighted by X, instead of the average of x weighted by Y.
The calculators is mine and I do as I want with it ;-), so I will put it here, together with a cash discount calculation/comparison. We assign the weighted average to the same key, i.e. GSB 0:
One of the typical decisions in my job is to decide on cash discounts - both when buying and selling. I want to compare the cash discount % with a yearly rate - and then decide. I put the standard payment days in Y, and the discount % in X, and get the equivalent yearly interest that I am getting (if I'm buying) or I'm paying (if I'm selling)
Here it is:
Here you have a small function missing in the 15c: the %T !!
I have placed it close to its siblings: in the GSB 7 key:
I loved its simplicity since I saw it in an HP41cv manual:
As I have mentioned before, most of my duties involve financial calculations in an industrial environment.
The calculator I prefer among all, because of its simplicity (no menus) and its portability (fits in my jacket and occupies very limited space in a crowded desk, is the HP15.
Here is a dump of the program memory:
Let's start with an oldie, in the version that appears in the Advanced Functions handbook - no change needed. It uses the A to E keys in User mode, following the standard n -i- PV- PMT-FV. One key for entering the data and placing the program pointer in the right place; then R/S to execute:
I will continue in the next few blogs with the rest of the memory. For the sake of engineer futility, I have left space enough for a 3x3 + 3 equation system if some time was needed - and it has not been the case so far !!