New owner of 41c seeks advice


I picked up a used hp 41c with a quad memory module installed for a decent price. I intend on using it for my graduate engineering coursework (mainly for exams). I was thinking of buying an x- functions module, but other than that, what other items would you recommend. Right now, It seems I'm working a lot with tensors.


Edited: 12 Sept 2012, 10:39 p.m.


I highly recommend the Advantage ROM. It has the Solver, Integrate, and matrix operations, among other goodies.



What would you expect to pay for one?


You should watch eBay for reasonable auctions around $80. some sellers ask for $125 or higher.


How about Diego's NoV-64 module ( ), and get several other module images loaded into it, including Angel's 41Z ( ). The Advantage module is great (I use mine all the time), but still inefficient with complex numbers. The 41Z gives a true 4-level complex stack and tons of more-efficient complex-number functions.

Edited: 13 Sept 2012, 12:29 a.m.


Appreciate the praise to the 41Z. Truth is it's one of my favorite projects - very close to my heart and resisting the passing of time very well.

And using it on the CL... well, it flies!


You can always turn it into a 41CL and not have to worry about which modules to buy.


I agree. I have never regretted my 41CL purchase. It has transformed my HP41.


41CL: ,

Yes, if you have a coconut 41c, which is likely, as opposed to the later halfnut, the 41CL would be the best. I don't go for it myself because I have a halfnut 41cx and I cannot get along without the time module portion of it, and separate time modules are nearly impossible to find.

The original HP-41's were internally code-named "Coconut" by HP. Later, in the summer of 1983, they planned to come out with a less-expensive version, partly by cutting the number of ports in half, hence the code name "Halfnut." They made it less expensive to produce and more reliable, but they ended up keeping all the ports, despite the company's internal code name for it. Halfnuts started shipping to dealers in approximately September of 1985. Today you can replace the original Coconut's logic printed circuit board with the 41CL board which is much, much faster and has ROM images for over 140 modules built in; but you cannot do that with the later Halfnut version. Since you have a 41c, not 41cv or 41cx, I suspect you have a coconut, not a halfnut, as the 41c was only provided in halfnut version for service replacements by the time the halfnut came out. Outside of that, 41's were all 41cv or 41cx by then. In spite of the jargon that flies around here, note that there never was one code-named "fullnut"!! No such thing. If you get the museum DVDs, you can read about the halfnut in the article "HALFNUT -- AN INTERNALLY IMPROVED HP-41C, CV, CX," by Richard Nelson and Jeremy Smith, in the CHHU Chronicle V2N4 (Jul/Aug 1985), pages 9 through 11.



Indeed, some options overlap each other having the same premise: using up-to-date technology - 41CL, NoV/Clonix series, MLDL2000 - OR keeping the old ones - Advantage module and so.

I have some of the original modules - X-Functions, Advantage - and some of the new - Clonix, MLDL200, 41CL (about to come...) - and it is necessary to say that you'll need:

- some knowledge and skills in electronics (or know who has) to convert your HP41C into a 41CL, or to build an MLDL200;

- some time to get acquainted to the new modules and their configuration/customization, or else they'll be kind of empty vessels;

- get used to the features themselves, or else they will be filled vessels not so easy to carry.

You'll have plenty of time if you are starting right now, considering the HP41 is a 'swiss knife' when you know the nuts 'n bolts, and once you are in the engineering field, your options are quite opened now, in the beginning.

My personal choice would be: having enough bux and the opportunity, grab a 41CL board and an X-functions right now so you can use your 41C with some features available in the X-functions you'll find in the 41CL when you update it. You can either evolve to the 41CL later or, have you (unfortunately...) found yourself in the verge of using something else, the 41CL board and the HP41C by itself will not be hard to sale (I'd buy them both anytime...).

I think both options to go ahead and to back of must be shown when we are in the very first stages and choosing. I must congratulate you for choosing a well recognized, classic tool for engineering, it won't let you down.


Luiz (Brazil)

Edited: 13 Sept 2012, 7:36 a.m.


I'd get a working card reader first so you can get programs in and out of the calculator.

When I was in school, I found the printer remarkably helpful. I'd set it on trace(?) mode while working through calculations. When I was done, I could look through the printout to verify my work.


Neither my 32-year-old HP-41C nor even my 27-year-old HP-41CX (both purchased when new on market) with its Advantage, Math/Stat, Extended Mem, and IR printer modules would be in the top ten HPs I'd choose were I back pursuing an EE degree. The 41C series has awkward and very limited complex number handling, and that comes only with the so-called Advantage module. It's extremely slow and display-limited. Yes, it was once undisputed king of handhelds...a third of a century ago!

Regardless, the HP-41C series units that I have owned do have the finest keyboard "feel" of any calculator I've ever used.

I'd choose for any serious use outside hobbyist calculator collecting an HP-42S, HP 50g, or HP-15C (but LE version only if you have no other choice). All have vastly superior complex number support (well, the 15C less than the first two) and are far more physically durable for daily use.


Thanks for all the feedback, there are quite a few options I wasn't aware of. First, you should probably know that I'm an experienced engineer, returning to graduate school after many years work experience. The calculator purchase was intended for in-class use (homework, exams, etc.). I foresee a lot of matrix and vector calculations (stress tensors). I know the Advantage module has functions to handle matrices and vectors, but what about Laplacian (or del^2) operations?

What should I expect to pay for a card reader?

Modifications such as the 41cl I'll leave for another day.


You can read Valentín Albillo's article about the Advantage module at . Again, check out the 41Z module mentioned above.

Instead of the card reader, I got the HPIL tape drive; but with the 41's constant memory, I've had some of my frequently-used programs in it for over 20 years, never re-loading, so I haven't used the tape drive on it in years (although I recently used it on the 71 because of a memory hardware problem).

Edited: 14 Sept 2012, 12:35 a.m.


Hi, again.

Jumping from an HP10C to an HP41C is relatively comfortable if compared to jumping from the HP10C to the HP50G. All RPN features are directly transposed, stack structure, transcendental functions and other features. Programming structure has been enhanced with arbitrary labels, controlled loops, indexed register and flags. Not to mention ALPHA and USER add-ons.

I guess many of us - I include myself - followed your request of what to buy after you have already chosen the HP41C. As you could see, other contributors showed other options for calculators and systems, but once you have set the course of action, considering other calculators seemed off course. I'm still fond to the HP41 system, and I am expecting to add two 41CL to the list... (almost here, almost here... about 80,000 minutes away).

If you need Matrix calculations, the Advantage ROM has most of the original CCD ROM features plus some more. I am not sure about other modules with matrices features, but there are some downloadable, new ROM's that might also add extra functionality for dealing with matrices (see the invaluable Ángel Martin's and others set), but you'd need 'vessels' to carry them (CLONIX/NOVRAM, MLDL2000, 41CL, etc...). The Advantage ROM and the CCD ROM exist as ROM modules.

As you are probably aware of, the HP15C is the closest HP10C's replacement with easy keystroke access to powerful matrix operations. This one is indeed a must have.


Luiz (Brazil)

Edited: 13 Sept 2012, 11:39 p.m.


There's a (large and apparently comprehensive) Laplace Transforms program for the 41 platform posted at TOS - link unavailable but you can follow the thread...


IMO the best tool for that job is an HP 50g.


HP41c Card Reader prices are all over the map. You can pay as little as $50, but will likely need the ever-present "gummi wheel" repair. For a good, working card reader the prices typically range from $95-$150 on eBay.


Hi mbrethen,

I certainly am an HP-41 enthusiast (the 41 was my 2nd programmable device - the 1st, I admit, was a TI-57). But, honestly, wouldn't it be much wiser to get a state of the art calculator (e.g. an HP-50) for your designated use?

All the Best (espec. for your exams),


If you do get a 50g, be sure to get a better manual than what comes with it. Hopefully someone else here can give a link to it since I don't seem to have it. I got a 50g a couple of years ago and after going through the manual that came with it I was absolutely totally turned off and really wanted to have nothing to do with it.


If you do get a 50g, be sure to get a better manual than what comes with it.

I agree. The printed "User's Manual" that comes with the 50g is useless for someone who isn't used to the 48/49/50 series calculators. It is more at the level of the pocket reference guides from the old calculators. The fact that it's 184 pages speaks to the huge amount that the calculator can do.

You can get Tim Wessman's Quick Start Guide here. It's a great place to start.

I prefer the "User's Guide" that comes on the CD. This has enough detail to help you learn the calculator without tearing your hair out.

Please note that the X<>Y function (called "SWAP" on the 50g) is the right arrow key. Tim's quick start guide mentions this but it's buried deep in the User's Guide and Manual.



The finest and, unexpectedly, lowest cost hard copies of HP 50G manuals are found at in the form of the Advanced User's Reference (691 essential pages in two volumes) and User's Guide (887 nice-to-have pages in two volumes). But the website says these both are on backorder until October 31.


Also note that right arrow doesn't work during entry, forever annoying me.

Edited: 16 Sept 2012, 2:18 a.m.


> Also note that right arrow doesn't work during entry, forever annoying me.

You can avoid the annoyance by doing this:

{ 36.21 SWAP 45.21 DROP 105.21 DUP } STOKEYS

This creates these new User Mode key assignments:

SWAP becomes left-shift-and-hold right-cursor,
DROP becomes left-shift-and-hold backspace, and
DUP becomes left-shift-and-hold ENTER.

Then turn on User Mode and leave it on all the time. If you make your key assignments strategically, you can leave USER mode on all the time without losing any of the standard keys.



I certainly am an HP-41 enthusiast (the 41 was my 2nd programmable device - the 1st, I admit, was a TI-57).
Although being in the other side of the ocean, if I am telling you about myself these words of yours would match to the commas and periods.


Luiz (Brazil)


Hi Luiz,

nice to see that you're more active again after a longer period of inactivity in the forum. Looking forward to reading from you :-)

All the Best, Juergen


Danke Schöen!

I was given (thanks GWB) a WP34S about two months ago and have not yet found the time to actually 'delve into' the calculator... But I hope as soon as I get the two 41CL and build the calculators themselves, I'll have no excuses NOT getting back to business...

Best regards.

Luiz (Brazil)


Muito bom dia Luiz,

You will find it worthwhile plunging into the WP 34S :-) Looking forward to your responses.




I looked at the 35s and 50g. The 35s will solve 2 or 3 systems of linear equations and can be had for relatively little cost online. Stefan's Matrix Multi-tool adds matrix entry and multiplication (but not of 2 matrices). The way it uses direct/indirect registers seems like extra work to me to store and recall variables. The 50g is more expensive and may be overkill for my intended use. I don't foresee a need for working with complex numbers; my course work is related to solid mechanics.

In summary, I need something that I can quickly get up to speed using. And have the ability to manipulate 3x3 matrices (stress transformations, eigenvalues, etc.), operate vectors: 1st order vector differentiation (gradients), 2nd order partial differentials (Laplacian).

Also, any programs I write need to be accessible throughout the semester.



Still, chances are your HP41C with quad memory, X-functions and a CLONIX module loaded with Advantage and some other ROM images will do the job. And your HP41C will have a free port for whatever you want to use, just take care configuring the CLONIX module accordingly. And if you have a NoVRAM or a NoV32 or a NoV64 instead of a CLONIX you'll have the chance to build a ROM with many programs (user code) and use them as extra features (you'll need another ROM image to handle this), leaving the whole 319 registers (41C + quad memory) for storing data.

Nothing comes for free, though... Some, little basic knowledge about the HP41 internals will help you going ahead exploring these features.


Luiz (Brazil)


Is Clonix an actual module you plug into the calculator? Where can one be purchased?


Yep! Please, try here and contact Diego. He'll surely make your HP41 happier!

I'd honestly go for NoVRAM if you plan to store your programs and use them extensively. Although CLONIX allows you to hold at least 6 ROM images, the NoV-series offer FLASH memory so you can easily build your own user-coded ROM images.


Luiz (Brazil)


One stumbling block I foresee is getting the roms onto the module. I do not have a windows machine to run the software (Unix or Mac only). I've emailed Diego, perhaps he can preload them.


That's what I'm hoping. This Linux user is not going back to Windows either.

Edited: 17 Sept 2012, 12:30 p.m.


I just can't avoid Windows for both my professional work and my (calculator) hobby but my main system is an iMac. Parallels with Win XP inside does the job nicely for me.


I wonder if it will also run under wine? Wine translates Windows API calls into POSIX calls on-the-fly.


Hi all,

As it often happens lately, many posts here gets under my radar, mostly while I'm between flights to/from Europe and Americas.

Thanks for the references to my projects placed by some users here (this makes me think that the Clonix/NoV modules are offering good service ;-) and that's what they were intended for.)

Some time ago I did check Mac Os functionality using a Windows box. If someone could shed some light on the Linux approach I'd appreciate. Several users have mailed me but regrettably I have not the tools (nor the knowledge) to properly reply.

Thanks again and best wishes from Caribbean Sea.



You might want to take a look at the "JMB-Matrix" ROM. The image and documentation are available at "TOS". This ROM is pre-loaded on the 41CL. I still think that you will be better off, dollar-wise, with a 41CL than the other alternatives, but I admit to being biased.

Now that I have multiple CLs I have a number of physical modules that I'm planning on selling if you still want to go that route. X-functions, Advantage, Stress, Structural, etc.



LMK if you decide to sell your advantage module.


I have two of them listed in the "classifieds" section.



I must agree with Monte: the 41CL is a dollar-wise option because of many reasons, and I myself point out two facts: it IS new, i.e., uses available components that can be bought these days, and has about everything you can think of 'stuffing' into the HP41 in one single shot, 'shake'n bake' ready (not quite, I know). Actual ROM modules once gone, are gone. Their images can be loaded anytime, though.

One could also point out that it keeps compatibility with most of what exists for the HP41 system, but this is kinda 'external'.
As stated, some biasing is needed so we can keep up with teh user needs...

And Monte, about the modules: how do you intend to sell them???? AHN???? Some o'them are interesting to have as physical units.


Luiz (Brazil)


Hi Luiz,

I was planning on making a list and posting it here in the ads section first. Then "that auction site" for whatever remains. I hope to get the list together in the next week or so.

Best Regards, Monte


Luiz, the list of modules that I have for sale is posted in the "classifieds" section.


... I'd make that list my wish list 8^D

I was aware of the possibilities of finding some 'wanna have' items, but I'd never guess some of them would come with the original instruction manual and box.

A couple of weeks ago I bought a partially destroyed HP41CV (I did not know what I was buying but the owner surely knew what he was selling) and it came with three modules: a Financial 1C, an X-Functions 1B (read about, downloaded the ROM image but this is the first time I actually see one of these) and an X-Memory, all of these are working items. The calculator mainboard is working, but the case will be kept for experiments (both half cases were glued to each other...). In my understanding, modules with exclusive hardware are the ones I'd need the most: Time Module, X-Functions & X-Memory, Test Module. And the original X-Functions documentation (manual) would be the very one I'd gladly add to the ones I have, mostly because it took me less than half an hour (there goes lunch time ) to read it all and test all functions back then, in the 80's. Fascinating! And I remember quite well the manual's typeface: typewriting machine in black (main text) and blue (functions and LCD data) colors, all beautifully arranged. Yep, one can say I ate the manual... but I was starving for new HP41 functionality!

Because it would be hard for me to get any one of these precious items, I'll gladly hope for some of us here to actually keep them, so they will be in good hands.

Congratulations, Monte, and thanks for allowing us to have access to them. In time: my brother bought the book and is taking it with the 'package'. I'm sure I'll not 'eat it' in half the lunch time, but I'll surely read it all. And thanks again (and as many times as I can tell it so) for the 41CL.


Luiz (Brazil)

Edited: 21 Sept 2012, 1:05 a.m.


Thank you for the kind words, Luiz. I accumulated the majority of these via auctions over the years before I got serious about the 41CL project. I doubt that I will recover more than a fraction of what I spent on them, unfortunately. Kind of like the 41CL project itself (and the book, too.) But I really do need to convert them into cash...

As far as the Time Module, I have a completed design (a 15mm x 25mm daughter-board) that can be used with the 41CL, but I haven't fabricated it because I expect that it is going to be too expensive for most people. I am considering moving the design to a different programmable logic technology, which would makes the parts cost significantly lower, but require much tighter design rules (like state-of-the-art) for the PCB. I'll post progress on the 41CL website if I decide to proceed.

Feel free to send me feedback when your CLs arrive (on the 41CL or the book.)

Best regards, Monte


If you have to do vector calculus the reasonable thing is a CAS (you can't perform differential operations on arrays of numbers... well, actually you can, the results are zero) You have just two choices, either the HP 50g (and relatives) or the TI-89 (and relatives). The first one has that capability out of the box for Cartesian coordinates, in the second one it can be implemented trivially.

Alternatively you can implement numerical differentiation (see for instance To put it bluntly, using a calculator for that is a waste of time and accuracy.

(I still think that doing those kind of calculations by hand is usually faster :) )


I've been learning Reduce CAS and use it with Antonio's I41CX+ app on the iPhone.

Possibly Related Threads…
Thread Author Replies Views Last Post
  WP 34S Owner's Handbook Walter B 5 2,689 11-09-2013, 05:34 PM
Last Post: Harald
  WP 34S Owner's Manual released for print Walter B 28 7,541 12-10-2012, 08:36 AM
Last Post: Walter B
  HP 50g advice Chris Smith 17 4,556 12-04-2012, 11:47 AM
Last Post: Peter Murphy (Livermore)
  HP-15C LE, wow! New owner euphoria. Sasu Mattila 16 4,304 09-07-2012, 06:55 PM
Last Post: lars Bergström
  One owner HP 11c Ethan Conner 2 1,315 08-11-2012, 09:13 PM
Last Post: Fabricio
  WP 34S Owner's Manual released Walter B 42 10,245 08-05-2012, 11:01 AM
Last Post: Etienne Victoria
  Advice on using the HP-50G Matt Agajanian 22 5,881 05-19-2012, 01:52 PM
Last Post: Matt Agajanian
  Restoring an HP-55, advice appreciated ! Alberto Fenini 4 1,681 05-15-2012, 03:43 AM
Last Post: Alberto Fenini
  Right, thanks to a typo, I am now proud owner of a HP71B Harald 22 6,205 05-10-2012, 11:34 PM
Last Post: Eddie W. Shore
  Advice needed John Abbott (S. Africa) 15 4,191 04-19-2012, 04:04 PM
Last Post: Luiz C. Vieira (Brazil)

Forum Jump: