HP 15c HP-42s or HP 41cx


I am looking to purchase a HP calc for my husband. He is a returning college student who always complains about his classes requiring a TI calc. He uses it fine when he needs to, but he's always talking about HP calcs.
I know he owns a HP-20s or two, but complains that they are not RPN or something. Which should I get him: 15c, 42s, or 41cx. He is a mathematics major/computer sci minor and will be using this pretty much every day when he isn't forced to use the TI. I think he owned a HP 32 a while ago, but from what I have read it doesn't do matrices, so that is out.
Which is the best choice for my hubby? If you give an answer, can you please explain in non engineering/mathematical terms as to why it is a better choice? Thank you.


I'd vote for the HP-42S,
because your husband seems to be used to the form factor, because he uses a 20S,
The 42S can easily do matrices with it's editor, has a two line display, is easily programmable, has enough memory for most tasks, and the batteries can last years.

There are more reasons for the 42S, but these should suffice for the first turn;-)

There are of course reasons for the HP-15C, or the 41CX.




All of these calcs are pretty hard to find for a decent price. All of them have different things that make them better for different purposes. The 15c has built in matrix functions. However, it has no output capability except to the display. But it is quite pocketable as is the 42S. The 42S also has built in matrix functions and further has infra red output capability to a printer so that you can have a permanent record of what his working on. The only input capability is through the keyboard. The 41CX has no built in matrix capability but it can be added through a module called the Advantage Module. The 41CX has several storage choices such as a magnetic card reader, a disk drive, and a tape drive. All of the information and programs saved on these devices can be saved indefinitely until needed. Altogether, the 41CX is probably the most flexible choice; but, you need to have more items to have matrix capability. The 15C is limited by having no output capability. In my opinion the 42S bridges the gap between the 15C and the 41CX pretty well, but has the disadvantage of having no long-term storage capability except in the memory of the machine. Any programs or information lost in the memory of the machine due to lock up or accidental clearing would have to be loaded again through the keyboard.


All of the machines will *work*

The 15C is probably the least useful (sacrilege, I know) for a CS major. But it cna be had for under $150 pretty handily.

the 42S (WITH THE RAM UPGRADE) is much more useful, and is probably the most useful dollar for dollar. An IR printer (the a model) can be had for under $60 generally, and the 32K RAM version should be available off and on for a reasonable price from fixthatcalc.com (I'd estimate under $300, perhaps as little as $250) - With 32K RAM you have enough room to model algorthms, code up some nifty time savers (network calculators, binary calculations, etc), and run some large matrices.

The 41(CX) has the most goodies- but you pay for the goodies. Estimate about $150 for a good working CX with maybe one useful module- $30-$80 each for extended memory (two), $100 minimum for a working disk drive, $30 to $100 depending on condition and type of printer, then there's the HPIL module, etc. (I'm a heathen. I love my 41CXs, but the calc that I CARRY as a computer professional is a 42S(upgraded)

the 48GX is also a great option if it is allowable. GREAT option. You can even code original computer languages in assembler on it. (but I still carry the 42S every day)


If $$$$ is not an issue, the Hp42s is probably a good solid choice (actually, you just named 3 of the best ever calculators). And you won't have to deal with hubby spending any more money on 41c periphials and ROM cartridges.

However all three are discontinued and actually quite sought after.

For a more powerful present day graphics, I suggest an Hp48G+ or a 48GX if you wanted to (or needed to) buy today.

Next month Hp will release a new line of graphics calculators that look to be really nice. However, they are not proven machines and with Hp's recent track record, could be loaded with Cockroaches or other nasty parasites (some seem to live on or eat batteries).

I use an Hp48GX and am very happy with it. I also have the newer and then discontinued Hp49G. The 49G is faster and has better software features than my 48GX, but doesn't compare in keyboard quality FEEL (I have heard from reliable sources that while the keyboard of the 49G doesn't feel as good, it is designed to outlast the older Hp's: I can't argue against this point because MINE WILL, but only because I don't use it!).

Two places to look for the three calculators you mentioned(and none are really reasonable for the average calculator user). As I stated earlier, the three you ask for are three of the best.


and ebay.

Else look at the Hp48G series. It is your best buy for the features and value (and handles Martices really well).


I looked at the HP 48gx and I don't think he wants anything like that due to the size issue. It looks as big as his TI calc. I read through some of the info on the 48gx and it uses RPL. I though I was looking for an RPN calc.


Though there are many who would argue this. It is keystroke similiar and to general use RPN.


Yes, RPL is different from RPN, but only slightly or greatly, depending on what you want to do! For hand calculations on the keys (no programming) they are almost identical, except that "number ENTER x^2" gives the square of a number in RPN, but "number ENTER ENTER x^2" is required in RPL (this is a very minor difference and in essentially all other things, they are the same). RPL also has an "infinite" stack and no "lastx" feature, but a 4 level limited stack, and lastx, are easily implememented on RPL machines (I got the "lastx" from someone here on this forum!).

The real difference between RPN and RPL is in the programming. It is a really significant change in thinking to go from a 32s type of programming to the 48 series or RPL language. Yes, RPL is more powerful, structured etc but for someone like me, a practicing engineer, it has been a significant learning curve to get proficient on RPL--in some ways it is like PASCAL or BASIC and so seems easy, but then in other ways is is not so clear.....

The "form factor" difference is also important. The 48 is really big. The 15c is beautifully small. The 42s is a very nice size. The 15c is significantly slower than the 42s--noticable with small programs especially if they use transendentals or trig.

The 41cv is generally less expensive than the 42s on e-bay, but you have to be VERY careful about damage to the battery compartment and broken screw posts (just ask lots of questions before bidding). If you want to do matrices, you must get a module (Advantage) which I don't think is all that expensive.

Also, look at the following:


it looks like HP is bringing out a new RPN programmable in the next month. yes, it looks different, but it is a possibility.


Bill Platt bill at plattdesign dot net

Edited: 11 Sept 2003, 11:28 a.m.


One other reasonable consideration. The Hp28S. He may like this machine (I don't). It will be fairly cheap, is smaller than a 48G (actually its direct predicessor), and still easy to get via ebay.

Buy one in as good of condition as you can get. Make SURE you get one with a GOOD battery door.

Feature wise, a really nice pocket calculator (if you have a slightly oversized pocket). Looks good.

But again if $$$$ is not an issue, I vote for a 42s.


As already stated, these 3 calcs are excellent, and they all have their + and - but at the end they all score in the same range.

I'd also vote for the 42S as it is the most powerful and the fastest of these 3.

Nevertheless I would also seriously consider 48GX and 49G+ for academic use. The CAS is a very luch advanced tool that really help when discovering new topics in maths. For a lower price than a nice 15C, 41CX or 42S you could find on ebay.


I think I have decided to go with the HP 42 since it has a few more features than the HP 15c and it has the same body style as the HP 20s.

Now, is the programming on the HP 42 the same as on the HP 41x?

Also, why did HP stop making this calculator if it was such a nice piece of equipment?



Hi Krystal,

THe 42s is designed to be compatible pretty directly with 41c/v/x programs. I am not personally familiar with this aspect, but have heard a bit about it:


scroll down to the "programming" part.

Sadly, it was off the market before I knew it existed--so I bought a 32sii instead (in 1996).

Maybe the 42s was discontinued due to the release of the 48 series. It is sort of like being a boat manufacturer---do you produce a 20' 22' 25' 28' 29', or do you drop the 28 footer?


Bill at plattdesign dot net


The 42S is supposesd to be compatible with programs written for the 41.

At a certain programming level, you might regret the full alpha keyboard on the 41CX, onlmy accessible with menus on the 42S, but other people swear that with a bit of habit it's not an issue anymore.

Anyway it is an excellent choice.


It is all a question of taste, but I would vote for the HP-42S. It is the only of the three that has a two line LCD, it has more memory, is faster and contains all the functionality that you would have to spend a fortune on special modules to get for the HP-41C(V/X).


Erik Ehrling (Sweden)



For every day use and cost effectiveness, my choice is a 4th calc, the HP48GX. If you are getting one because he always wanted one of those 3 calcs that is different. I have had and used the 41C, 41Cv, and the 42S. I don't use any of them anymore. I have borrowed and used a 15C, but didn't like it. After using the 48GX, I am sold on it's performance. I now own 3 of them as well and use them in my work as an R&D Engineer.

I think the 3 machines mentioned will all be more expensive than a new 48GX, but will be less capable. The size makes a difference to some, but not to me. I don't walk around with a calc in my pocket. Ever. If I go to a meeting, it is not really all that big to carry with me. For longer hikes to another building, I always take my briefcase/bag with me anyway. The 48GX is powerful, has tons of software and programs for it, and is easy to use.

It's your choice of course, but collectors have driven the price of the 3 calculators that you mentioned to collector level prices, not daily use affordability. While still expensive, the 48GX is available new, has later technology, and is durable. It was billed as the supreme engineering calculator and it's longevity and popularity support that claim.

As for RPN vs. RPL, I really can't tell much difference in use for the most part other than the stack difference.

As a bonus, you can pick up a 48GX, 48G, or 48G+ pretty cheap on EBay compared to the other calcs you mentioned.

Good luck.


Krystal wrote:

"Hello, I am looking to purchase a HP calc for my husband. [...] I know he owns a HP-20s or two, but
complains that they are not RPN or something. Which should I get him: 15c, 42s, or 41cx. [...] If you give an answer, can you please explain in non engineering/mathematical
terms as to why it is a better choice?"

The ideal choice would be an HP42S. Reasons:

  • Same form factor as the HP20S. If he's used to that
    and only regrets it not being RPN, the 42S is same physical quality, like shape, but much more powerful, and RPN to boot. It easily fits a shirt pocket, try that with a bulky 41C.

  • The HP42S is much faster (more than 15 times), has
    much more memory (more than 15 times) and is much more capable than the HP-15C, and the same applies re the HP-41
    He will be able to do all kind of matrix manipulations with utmost ease, as well as many other advanced functions, while using glorious, classic RPN.

  • The HP42S has a fully alphanumeric, graphic, two-line display, whereas the other models feature a non-graphic, one line display. This will allow him to clearly see all messages and results with full prompts and texts, and even some small but useful graphics.

Matter of fact a small routine can be prepared that, the moment your husband is presented with and turns on the machine, it will display an "I LOVE YOU" message on the display, complete with music and even a big, graphic heart and all!!.  It would make for the nicest surprise, don't you think ?  :-)

Best regards from V.

Edited: 11 Sept 2003, 11:43 a.m.


I forgot to mention the graphics.

They really do matter. For minehunter and yahtzee (still working on that, using the dice roller code on the site)

But also for plots (I admit to using this as a technically allowed cheating aid - the prof never believed the the calculator was programmable and allowed it on exams- to help me sanity check some solutions.

-oh, and the statistics on the 42S are great, and very expandable.


Keing in the program is an excellent exercise for both alpha keyboard learning and debugging techniques...


Don't forget the yahtzee program over at my site for the 41/42 series. Works well and is just waiting for some graphics. :-)



AH- that should make the whole project a lot faster :)

thanks, Gene!


How many "Don Juan" helping you, milady. ;-)


Hi Krystal,

The 3 calcs you mentioned are among very best HP manufactured and I understand your dilemna: none of the 3 can totally outperform the other 2 in every aspects:

I) 15C
- Strenghts:

1) Very nice form factor, the best ratio features / volume ever and probably the "most classy" award
2) one of the very few calculators to feature a complex stack (the first one actually)
3) limited but nice matrix integration (you can even recall a matrix pointer of the stack, long before the HP28/48 series)
4) complete set of advanced features accessible directly from the keyboard (hyperbolics, random number, combination & permuation, gamma, solve, integrate).
5) Recall arithmetics (RCL+,...) and all 12 conditionals.

- Weaknesses:

1) -Very- slow...
2) No alphanumeric display. Not even an alpha display of program steps, which makes programming (otherwise quite powerful) and degugging a -real- pain.
3) No I/O whatsoever. Don't even think about exporting or importing a program...
4) Matrix handling looks nice on the surface, but actually requires a lot of key stroke to enter a matrix, even in "User" mode - which is not even as convenient as the '41 Advantage module, supposely less integrated. Complex matrix is a nightmare (you need to enter the matrix in real form, call a matrix function to transform it into a complex form, and convert back after finishing the operation).

II) 41CX


1) The most flexible calc ever, due to the expansion ports. No other calc can claim to be as versatile: advanced math, finance, aviation, chemistry - everthing is there. But you need to pay for extra modules.
2) I/O: Provided you buy the necessary hardware (again...), you can load/save programs with various kind of hardware.
2) Very good handling of alphanumerics, with letters directly accessible on the keyboard.
3) Extended memory: this offers a lot of flexibility, especially the ability to manage files (ascii or binary).
4) Timer functions: if you want to use your calc as a clock/"PDA" (less useful nowadays - but this is a myth as the NASA made HP build the time module to take the '41 on board the space shuttle in 1981).
5) Synthetic programming: The calc is a hackable machine that allows to enter extra instructions (some kind of machine code) - while neither 15C or 42S can. But you need to have a 'hacker' mind...
6) Prestige: Along with the '48, the '41 is the most mythical device ever produced ! You have to remember that the first version (41C) was out in 1979 (i.e. prehistory) and nevertheless is still a very useful tool today !


1) Quite slow (but still twice faster as the 15C).
2) Quite big (not pocket-friendly, due to the expansion ports).
3) Will cost you a lot in add-on modules, cf. next point.
4) Lack of build-in functionality (this is a deliberate choice - the machine is meant to be expanded, hence there are few built-in features). Compared to the 15C and the 42S, the '41 is especially lacking a complex stack (even the Advantage Module only offer a 2-number "stack" implementation, not very ideal). But you may not need to compute complex operations. On the other hand, matrixes are quite well handleded by the routines of the Advantage Module: although they are not as integrated as those of the 15C and the 42S, they do the job very well and offer additional functionality of its 2 competitors (especially for matrix manipulation).
5) Lack of recall arithmetics and only 10 conditionals (minor point to me anyway).
6) Lack of Gamma function, combination and permuation, random number - all of which are easily programmable and some of which being present in the PPC ROM, so, not that much of an issue (if you can find the ROM).
7) No named variables as on the 42S - you have to deal with registers only, which makes it hard to remember what you really wanted to do in a program when you review it after a long time.



1) The almost perfect calc: The programmation power of the 41, the features of the 15C, and much more.
2) Elegant and pocket-friendly.
3) Very fast
4) Smooth and nice complex & matrix integration. Just as the 28 or the 48, can handle various object types on the stack (matrix, complex, strings - but no lists, programs, or algebraic expressions/equations).


1) No other I/O than I/R one-way printing, which is -a shame- for a calc of this quality. No other way to input a program than your fingers. That's why the '41 survived still for 2 years after the 42 release. The 42 was actually more a 15C upgrade than a 41C upgrade, and only the 48SX would definitely berry the good old 41. A 42SX project was sadely cancelled (probably not to undermine the '48 sales).
2) Ackward alphanumeric entry. No matter how people can claim that you can get used to it, the fact remains that you will never type a text a fast on the 42 than on the 41, simply because each letter requires 2 key strokes instead of 1. If you are very keen on using your calc as a memo pad, I strongly recommend you choose the 41 instead.
3) Limited memory (8K, which is little more than a '41CX with 2 extended memory module). A 32K upgrade is possible, but is a very manual operation and you will have a hard time to do it.
4) No time function - but these are not so useful on a calc nowadays.
5) No extended memory, meaning no "files" as on the 41CX. You can type additional text editing programs, though. But again, see my point on the '42S alphanumerics entry...
6) No way to enter complex numbers in a different mode than the dislay mode (rectangular or polar). An "angle" key like on the 48 would be welcome.
6) No algebraic equations for the solver. The more recent 32SII added this handy feature (while I love RPN, I think that it is easier to type 'P*V=N*R*T' than ' LBL "GAZ" MVAR "P" MVAR "V" MVAR "N" MVAR "R" MVAR "T" RCL "P" RCL "V" * RCL "N" RCL "R" * RCL "T" * - RTN' :) A matter of choice..
7) A 42SII could also have introduced the very nice fraction support of the 32SII.

That's it for now :) Other points you could consider:

1) If you do not need matrixes and are not too demanding on complex numbers, you can go for the 32SII - simple and solid.
2) If you want power of RPL in a nice format, the HP28S is a good alternative.
3) If you have a Palm device and do not mind using a sytlus instead of a keyboard, I recomment the "P41CX" '41CX emulator for PalmOS from Charles (www.palmgear.com). You can have *all* 41 modules for a mere $10. The emulator is very good. If you own a PocketPC, you might want to look at ev41, or the very good Pocket15C 15C simulator (www.lygea.com).

My 2 cents.
Vincent Weber

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