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Musings and comments about our common interest


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How I have configured my HP15c for financial duties (III)

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:



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How I have configured my HP15c for financial duties (II)

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:


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How I have configured my HP 15c for financial duties

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 !!

Time Value of Money
2 STO 1
3 R/S
4 GSB .1
6 R/S
7 RCL*0
8 RCL 5
9 X<>Y
10 -
11 LST X
12 RCL+3
13 X=0?
14 GTO .0
15 /
16 CHS
17 TEST 4
18 GTO .0
19 LN
20 RCL 6
21 LN
22 /
23 STO 1
24 RTN
25 LBL B
26 STO 2
27 R/S
28 ,
29 2
31 EEX
32 CHS
33 3
34 CF 1
35 SOLVE .3
36 GOTO .4
37 GOTO .0
38 LBL .4
39 EEX
40 2
41 *
42 STO 2
43 RTN
44 LBL C
45 STO 3
46 R/S
47 GSB .1
48 GSB 2
49 CHS
50 STO 3
51 RTN
52 LBL D
53 STO 4
54 R/S
55 1
56 STO 4
57 GSB .1
58 RCL 3
59 GSB 2
60 X<>Y
61 /
62 CHS
63 STO 4
64 RTN
65 LBL E
66 STO 5
67 R/S
68 GSB .1
69 RCL+3
70 RCL+7
71 CHS
72 STO 5
73 RTN
74 LBL .1
75 SF 1
76 1
77 RCL 2
78 /
79 LBL .3
80 STO 8
81 1
82 STO 0
83 +
84 TEST 4
85 GOTO .0
86 STO 6
87 F?0
88 STO 0
89 RCL 1
90 CHS
91 Y^X
92 STO 7
93 1
94 X<>Y
95 -
96 X=0?
97 GOTO .0
98 RCL*0
99 RCL 4
100 RCL/8
101 *
102 F?1
103 RTN
104 RCL+3
105 LBL 2
106 RCL 5
107 RCL*7
108 +
109 RTN
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New flashing service

Today I have received a USB to com adaptor. Since most of our computers are laptops and quite new, we did not have serial adapters. I have then proceeded to update a 12c+ with the latest available software. In this particular case, it did not increase speed (it was already 150 times faster, so I am not deceived), but it corrected a number of issues compared with the original firmware.

We have decided to offer firmware flashing as a service for our purchases of a calculator. It will have a 10 € charge. The rules:

  • Calculators elegible for firmware flashing are HP10bII+, HP20b, HP30b, HP12c (ARM version)
  • The customer supplies the firmware through email.
  • The calculator to be flashed will be a new, out-of-the-box (or plastic package!). The serial number and proof of purchase bits of the packaging will be included in the shipping to the customer. (It is the customer decision to register the calculator in HP's website). Sorry, we will not flash calculators not brand new!

One of the most exciting projects is the repurposing of the hp20b and hp30b financial calculators with ultra-slick scientific firmware. The project is called wp34s and is run by Marcus von Cube, Walter Bonin and Paul Dale (in no specific order!).

You can find it on

There have been a number of releases (build number was 800 at the time of writing), and you can check whether you like the software by running the included .exe file and testing the features. The .exe file has the advantage of having the right labels on the keys!

I have not yet tested the flasher cable and software on a HP30b but I plan to do it shortly. I will then report on the results!

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If you always envied the young look of your colleague's Casios and Texas...

Please take a look to the Blue-white HP 50g


It sure doesn't look engineer-like but school-like; but then, most of my customers for this product are in college!

There have been discussions as well about label contrast and readability - despite its looks, methinks this one scores high. Take a look at this close up. Sorry for not taking it out of the sleeve - I do not intend to use one myself. But for collectors: I have available as many as you want!


This is the presentation - exactly like the "normal" one. I have found it just in Spanish/Portuguese, while it could be done in any language, if volume was enough:




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The new HP10bII+ has arrived!

The new HP10bII+ has arrived!

A complete review will appear in a future blog instalment - I am too excited to wait for that and will just give you my first impressions.

While I love RPN machines, I have to accept that this one clicks more than some buttons in my heart. Three pictures will suffice to see what I mean:

Look at all buttons filled with blue and organge shifts!

You can see the typical financial keys, but there are as well mathematical functions like trigonometrics, inverse trigonometrics, Hyperbolics, date functions, and several useful additional features, like breakeven analysis (in all the companies I have worked for, the breakeven calculation (how fixed costs, variable costs and units sold relate to reach a given result) is used to predict the monthly results)

Now look at the screen:


Readability is very high, and the metallic trim looks classy - in fact, the whole calculator looks classier than the 20b and 30b. Key click is miles ahead of the 20b and similar (altough different) to the other calculators (30b, 17bII), and better than the 50g - surprising on an entry level calculator.

Finally, take a look at what I found when I opened the battery door:


You can see the same connector that appears in the HP12c+ - which means that this calculator may be re-flashed to update software - or to repurpose it. I understand it uses the same ARM processor as the 12c+

At this point in time I have not dared to disassemble it - to check if there are more connectors inside.

The machine has the lower round edges of the new HP generation (20b, 30b, 35s, 17bII+ silver), that greatly enhances use with a single hand (opposed to Pioneer series). although it is substantially thinner. I stress that it does not look cheap at all - in fact, it looks more expensive than the 20b (and has better keyboard, too) and the 30b.

I would still give the nod to the 30b - it can be keystroke-programmable while the 10bII+ cannot.

I have as well a sweet spot for non-menu calculators. In many cases, when you are in a meeting and everybody expects your answer, it is painful to navigate the menus to find the right one for your application. While the 30b keys can be assigned to specific programs, it is more cumbersome to do so. I have long favoured the 15c as my all-terrain calculator. I can understand the 10bII+ can be the same for a non-RPN calculator user.

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A trace mode "accountant type" for the HP 50g

If you have an HP 50g and you want to print something, your best way to printing is the HP 82240B. The distance betwen printer and calculator must be very small (around 1 inch), and the list of printing commands is not too big, in particular if you want to print accounting calculations like you would do in the 17bII.


I am sorry to come back to finance-related things. Most of my readers will be typically science-oriented folks; but many of us end up as well in jobs that involve "bean-counting": if we run a project, we need to control the budget; we need to justify our investments with NPV, paybacks and IRRs. And in that respect, we are disadvantaged with our fantastic graphic calculators.

Sometimes I just want to mimic the printing of a list of additions and subtractions that the guy sitting besides does with his lowly, chain-entry, printing calculator, with my HP 50g. So I said, "let's switch to trace mode". Oops. There is no trace mode. There is very limited information about printing. How come I am not able to print just like the HP 17bII was able to do, twenty-something years ago?

The advanced users reference book talks about vectored input: two variables, alpha-ENTER and beta-ENTER, that are executed before and after of the command that is in the command line. It requires flags 62 and 63 to be set, and 34 to be off. It is intended for a "programming trace", that is, printing the whole stack at each step.

I have modified them to be more similar to the typical "accounting trace" mode of the HP 17bII. It requires also to set automatic linefeed off, i.e flag 38 ON.

Here it is:



<< PR1 OBJ-> >>


<< "[" SWAP + "]" + PR1 CR DROP PR1 CR >>


Both Alpha and Beta need to be written with the greek letter, i.e. right-shift A, right-shift B

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A comparison between HP 17bII, HP 17bII+ gold and HP 17bII+ silver

I wanted to check how the new designs fare when compared with the old Pioneer series. Here you have my impressions:



Key feel:

The original HP 17bII wins, hands down. Second, and not too far from it, the HP 17bII+ silver. The slanted keys of the latter are more comfortable to put the finger on, but the rounded keys of the original model are not too bad. (In the current line, I still prefer the ARM 12c but not by much)

The gold HP 17bII+ is a very distant third. There is a plastic, hollow feel to the keys that is not so agreeable as with the rest. However, there is still a healthy keystroke feedback.

I have lost a couple of keystrokes with the gold model. Not enough experience with the silver. Never with the original one.

Of course, for those of us for whom the double sized ENTER key is fundamental, the gold is again in the last position.


The rounded lower edges of the newer silver model make it more comfortable to handle it with a single hand. The fingers can better reach farther keys. The original's more square body makes it a little bit uncomfortable, but the thinness helps - while the gold is awkward to handle.



Here the ranking is: 1st silver, 2nd gold, distant 3rd the original one.

The contrast in the original is in another (lower) league.

It is worth noticing that the screen in the newer ones has provision for trigonometric modes (GRAD) and the upwards and downwards triangles - it is HP 42s- ready!!!


I started to use this calculator around 1990, when I betrayed the engineering profession and started an MBA. It was my work calculator for the best part of 10 years, so I am quite familiar with it. At the moment, and coming from the scientific line, the fact that there were many f-keys left empty made one feel that it was an inferior product. But then we realised that the solver tool was very powerful, and that with a little ingenuity you could program most anything you needed.

This is still the case with the new models, but seemingly in the latter models some functions have been left out compared with the original (the Let and Get ones). In any case, these functions were not referenced in any manuals that I know, and were discovered by using HP 19bII programming in the 17BII.

The new models include an additional menu for currency conversion. I have 2 units of the old model (one bought in Europe and the other in America), and one has the currency exchange menu (the European one) while the other does not. However, even the European one does not handle the Euro - they could not predict it at the time!

Having the 19BII+ with RPN, it was understandable at the time to handicap the 17BII with respect to the upper model, by taking out the trigonometrics and other functions; however, now the HP 17BII is THE upper model in the range - a little effort could have been done to complete the function range of the HP 17BII with the rest of the functionality of the 19BII.

(The latter was an excellent calculator - seeing three lines of the stack was a great help to plan you calculations, but the ugly and uncomfortable layout made it difficult to be used in real life. The reliability of the battery door made it a nightmare as well - most of my friends got theirs broken, and fixed with electrical tape.)

The memory is 8 kb in the first model, 32 kb in the newer ones.


We put the following function in the solver:


HP 17bII original: 81 seconds

HP 17bII+ gold: 78 seconds

HP 17bII silver:172 seconds

The 17bII original was based on the Saturn processor, while the silver is based on the 8502 processor. It is amazing that an architecture designed in the early 80 can compete with a current production processor - until you realize that the 8502 was the Commodore 128 !!!.

There is nothing new under the sun...until the ARM based machines came in!!

A final comment: For utilisation in the real world, any of them beats any other calculator in the line up. The menu logic is better than the 30b (despite its extended functionality and programmability.And you can do a lot of things more than the 12c/cp (while the latter portability makes it better for the jacket pocket)

If you can at all afford it, even after so many years, this is still the one to have!!

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Just received my first 30b - first impressions

Today I opened the box of the 30b and had my first stint with it. I will do a formal review in some time from now, but cannot avoid making some comments on the fly.


To give a reference, I think that the best financial calculator is the HP17bII - from the viewpoint of having all of them. I think also that the latest HP17bII+ is the best of all, followed by the first HP 17bII.

I have been surprised by the 30b. It has an amazing number of functions, including hyperbolics and inverse trigonometrics. SIN, COS and TAN are not even hidden in menus. It has menus for a number of items that we had to program in the past. The menus, although not as efficient as the screen keys of the HP17bII, are surprisingly logic. It took me all of 2 minutes -without looking at the manuals- to figure out how they work. (I have the break even formula programmed in a way or another in all of the calcs I have - now I have a specific menu for it). Date menus are very intuitive and contain DATE+ and DDAYS within the same menu (just like the calendar functions of the 17bII) Overflow is at E499, instead of E99. Factorial is applicable to real numbers (really a gamma function then). I see 12 significant digits. A curious feature is that you can edit the number in the screen anytime - even when it is a result!

I see it as a very all-weather, all-terrain calculator: so far I have not seen anythin I do on a daily basis that I cannot with the HP 30b.

Keys are clearly better than the competition, but still not at the same level of 12c or 17bII. Still, a very clear feedback and had no missed or duplicated keystrokes. Screen is well protected by the bevel at the border, and it has a good contrast. A small criticism: the black shiny back keeps all the fingerprints until cleaned. It is a very light machine as well, not as classy as the 12c or the 17bII but much better than the 20b.

There are many areas that I have not explored yet - like programming, decimal logs, Black and Scholes, etc.

Stay tuned for the full review!

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The HP85 and my 7 year old

This last Saturday my 7 year old asked me about the green suitcase in the mountains cabin. "What's this, Dad?



"A portable computer, Guillermo"

"That big? Can I see it?"

"Yes you can"


"What can you do with it? Can we see YouTube with it?" (sometime ago he asked me "when you were a child, did you like to use Google?" How to explain that there was no Youtube, no Google, no www, and in my case, no network even around 1981 )


"No, you can't"

"what can you do with it, then?"

"You can make programs. You instruct the computer to do what you want"


"you are joking, aren't you? Does it work?"

"Yes it does. See?"


"What's that thing on the right?"

"A tape drive. It is like a USB memory - just slower and with less memory. You can write your programs in it, and you can retrieve other programs other people have written. Do you want to tell something to do to the computer? Let me help you."

"OK. Let's have it print 'IRONMAN' on the printer.


20 END

"OK. How can it print it many, many times?"

"Let's try"


20 GOTO 10

"Isn't GOTO misspelled?"

"No. It is a program keyword. It is not English. It is a computer language, similar to English. It is used to give instructions to the computer. Let's try something else. Now you are learning how to multiply. Let's have the computer print the multiplication tables, OK?"


10 REM GUILLERMO'S MULTIPLICATION TABLES (some explanations on what is a comment)


30 INPUT T ("T is the name of a box where we put the number we want to print the table for. It is called "a variable"")

40 FOR I=1 TO

50 PRINT I;" X ";T;" = ";I*T


60 END

"Dad, can we tell the computer to play a game?"

"Yes, we can, but that'll take longer. Besides, you need now to do your homework. Next week end, OK?"


It had been a wonderful afternoon. He was hooked. Next week we will try to do some drawings.

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