Why is the HP 42s so expensive?

OK, I give in! Why is the HP 42s so expensive on the used market? Prices between $300 and $400 seem to be very common on The Auction Site That Must Not Be Named. I've just been offered one for $275, and honestly I'm sorry to say that I'm tempted, because anything that expensive must really be the bee's knees, right?

I've never used one -- I went straight to the 48SX -- so I'm at a loss. What makes the 42S worth so much? Are they really that good, or are they just inflated because people buy and sell them for the monetary value alone? (I prefer to use my calculators, rather than let them sit. They're only worth money to me if I find them a pleasure to use or play with)


OK, I give in! Why is the HP 42s so expensive on the used market? Prices between $300 and $400 seem to be very common on The Auction Site That Must Not Be Named. I've just been offered one for $275, and honestly I'm sorry to say that I'm tempted

Buy it, resell on The Auction Site That Must Not Be Named, then use the profit to buy a shiny new HP 35S or two.



Good question! First, the 42s was the successor to the VERY popular (and some would say, industry-changing) 41 family. It sort of brought the best of all worlds to a much smaller form factor, and I think the intention was (at the time) to be the "ultimate" calculator in every way. Those who wanted all of the power of the 41 family -- without needing the expansion capabilities -- were in heaven. It was also a serious scientific calc, highly programmable, fast and it looked great. So it appealed to almost everyone.

Some will probably say that the 42s was the peak of perfection for the classic HP calcs. The 48sx went a completely different way, so it was hard to compare the two families. A different programming model, a completely different display, different approach, etc.

Also, the 42s is much harder to find than the 48 family, of which there are still zillions on the market. Scarcity makes for higher prices.

My all-time, pick-only-one favorite calc is probably the 19c; it's just way cool in a nostalgic way for me. Yet even with that said, and even owning 20+ other HP calcs all the way up to current models, I still think the 42s is one of my most favorite calculators. I would venture to say that a lot of people feel the same way. That's one reason why they are so expensive and highly desired.

My $0.02 anyhow. :-)



The 41C is still very popular, judging by the numbers that get posted to the nite that must not be samed. The 42S is compatible with the 41C at the user code level. There are many, many more 41Cs out there than 42Ses. Perhaps those two facts account for the premium price the latter commands.

If you just want to see what all the hubub is about, without laying out a lot of cash, go get Free42. It's a very nice and faithful software implementation of a 42S that runs on an incredibly wide set of platforms. Admittedly, clicking buttons on your screen is quite different from pressing keys on a real calculator. But aside from that, Free42 can give you an accurate picture of what the 42 is like to program and use.

I'm in the camp that says the 42S was the zenith of RPN keystroke programmable calculators. I need to revisit this opinion in detail with the recent release of the 35S, but my gut feeling is that the 42S still retains the crown. Even so, the 42S wasn't perfect. The lack of external I/O other than printing was the biggest flaw. But the 42S is also 20 years out of date now, and it's age shows in the slow CPU, small screen and limited memory. I'm still waiting for the machine that the lineal descendant of the 42S would have been, if the line hadn't abruptly veered off into RPL. The very nice HP35S gives me some hope I may see that one day.



Let me say the 42s

  • contains the most RPN calculating power per volume (cm^3 or milli-pint or whatever unit you prefer),
  • is comfortably programmable (alphanumeric display of steps, sufficient memory, alpha labeling),
  • has a very clean and elegant keyboard (almost hiding its power, comparable to Apple's iPod),
  • lives many months with one set of tiny batteries,
  • and is still shirt pocket size.
It's the *only* calc offering all this! Reasons enough for prices going high. Only the 27s and 32s (not sii!) present the same clean surface, but the 27s this is neither RPN nor programmable, and the 32s has less power in many ways. RPL calcs offer more power and a lot more features, but are too large (not for normal shirt pockets anymore), and way too complex even for many willing people of the community (as has been discussed here many times). Pulling out an HP42s in a meeting is understatement, doing the same with an HP48 would be the opposite.

IMHO the 42s would be a *perfect* pocket calc even nowadays if it had I/O and a better LCD. Any further upgrades would be just the cream on top, as people say here.

HTH, Walter


Have you read Valentin's
Long Live the HP42S! article?


My first collector purchase last year was a 42S and I got really soaked on it--over $300 for basically a field grade unit (name branding and a face plate that eventually needed flattening and regluing), but that included manual and box, which i am told drove up the price. It also works fine but I am forever disappointed with the wimpy display. I love Thomas Okken's Free42 and just had to have the real thing. I must confess I am glad I have the 42S as a collectible, but my main 42S work is actually done in Free42 on the computer or Palm--much faster, and there is I/O! I love the IDEA of the 42S, but I am just not in love with the real thing.

If that doesn't scandalize some here, I have a near mint 15C that I barely use. Just can't seem to get that fussed about it--and I paid a goodly sum for that too! I just can't get past the idea that, in benchmarking, it is so damn slow.

Let the indignant replies begin!



I'm in the camp that considers the HP42S to be the best RPN calculator yet made. I bought my first HP (HP-67) in 1976, and I've collected some 30-odd other HP calculators in the interim, so I've used many HPs in the past 30 years. My 24-year old HP-41CX and 21-year old HP-15C don't come close to matching the functions contained in the HP42S, nor its speed (five times that of the HP41C or HP-15C) and precision.

Unfortunately I didn't decide I wanted one until 1997, two years after the HP42S was discontinued. Even then the HP42S was almost as unobtainable as it is today. I was really lucky to find two new units in stock at the nearby University of Alabama at Huntsville bookstore for $114 each. They had been there unsold for four years, and had long dead batteries. You better believe I bought them immediately.

One of the best things about the HP42S is its full-spectrum support of complex number calculations. If a complex result is appropriate, it appears naturally. Try calculating the square root of -3, the arcsin of 1.5, the natural log of -5, etc. on most machines. The HP42S will return the appropriate complex domain answer.

The other thing I like is the ease of performing matrix operations.

These two categories of operations are far far easier on the HP42S, compared to the HP-41C or HP-15C. Complex number support of the HP32S, HP32SII, HP33S, and apparently the new HP35S is far inferior.

I have never found the 8K-byte RAM of the HP42S to be limiting in any practical sense. My largest program is a full-blown fourth-order Runga-Kutta differential equation solver, about 330 steps. I still have plenty of RAM left with it and several other programs in residence.

Currently, the calculator I use most often is a HP49G+, whose capabilities far exceed the HP48GX and HP42S. But I much prefer programming in RPN on the HP42S, rather than the RPL of the HP49G+. I'd really like to have a HP50G type of machine that had a choice of programming models...either RPL or RPN.



Previous respondents have already mentioned some of the reasons why people like the HP-42S, but there are still a few things missing in their replies. Here's my attempt at a eulogy:

  1. The simplicity of RPN and keystroke programming. While not as flexible and powerful as the RPL language of the HP-28 and 48/49/50 series, RPN and keystroke programming are easy to learn, and you'll be able to write interesting short- to medium-size programs within days.
  2. Fully supports the (unextended) HP-41C instruction set, including unlimited separate programs, multi-character alphanumeric labels, the ability to use any register as an index register (including the stack registers), lots of flags, and powerful loop control instructions.
  3. On top of the HP-41C programmability, the HP-42S has named variables, which can be used to store real and complex scalars and matrices, and 6-character alpha strings; all stack registers can hold all of these data types as well. The use of named variables can make programs easier to read, and it also works with the INTEG and SOLVE commands, which use menus much like their counterparts in the RPL series.
  4. While you can limit yourself to the HP-41C instruction set (HP-41C programs run without modification), by using the programmable menu and variable menu, you can spiff up your programs with self-documenting user interfaces -- and all of this is remarkably easy to learn and use.

This combination of features beats all other keystroke-programmable RPN calculators hands down, at least in terms of programming power. Nitpickers may point out the HP-42S' lack of I/O, and one or two areas in which the HP-15C's complex and matrix functionality are superior, but then you gradually move into the area of religious debate. ;-)

- Thomas


You guys seem to have said it all.

Valentin's article on the Advantage ROM for the HP-41C series states that "you'll never, ever, look at 15C/42S users with "envious eyes" (or to any other model for that matter)". I tend to agree with this statement, however the 42S is a fantastic machine and worth aquiring at a reasonable price.

I 'almost' had a pristine 42S a couple of years ago; a secretary at work posted a lost and found message about a calculator. When I inquired, it was in fact a like-new 42S without a case that someone had left in a washroom of all places. She wouldn't give it up until a reasonable amount of time had passed to give the rightful owner a chance to reclaim it. I loved the interface and form factor of my 32Sii and really wanted that calculator! I offered to pay for it too.

I kept checking in with her periodically until a few months later when she proclaimed that a full year would have to go by until she could let me have it, just in case... Long story short: after a year had gone by, she told me that she had given it to her 13 year old son who didn't really understand it but wouldn't give it up, even for a top-of-the-line TI graphing calculator. Go figure.

I use the Free42 on occasion, but I am partial to the 41C (fully-loaded) and the 15C, despite their relatively slow speed compared to the 42S. The 15C is the one that got me through Mech Eng. Heck, for fast calculations, there is always the 49G+.

My recommendation is to buy that calculator. You will not regret it if you like HP calculators.




but then you gradually move into the area of religious debate

Gradually? Funny, I never though of micro and milli-second posting response times being a gradual thing :)


Hear hear, Thomas.

The 42S is the absolute best of the programmable RPN models in terms of its breadth of functions and ease of programming. I just wish I could have one with unlimited memory that ran as fast as a modern PC. Oh.. wait.. 8)

Seriously, I kvetch about the lack of I/O and the slowness of the 42S, but I'm delighted to have mine. (It's one that can switch to "turbo" mode with a little hackery, so I get some of my speed need met.)

But I'm hard to please, so I keep wishing for a modern version. And as long as I'm at it, I wish for one whose design is driven by technical and aesthetic concerns, and not by the need to be a viable product in today's marketplace. At the same time, I wish this calculator were wildly popular, so that a large community of users would arise and bring back the glory days of the PPC, but with a GPL and web flavored modern twist.

It is all quite illogical. My id gets the better of me sometimes.



Maybe the question should be, why is the HP15C so expensive? That really baffles my mind.


Oh come on, please start a new topic :-)


Are you the topic police? I feel my comment is within the topic of "expensive" machines therefore it does not require to start a new topic. And unless the moderator tells me otherwise I am going to leave it the way it is. But if you disagree you have a choice, just do not read it.

Edited: 18 July 2007, 3:00 p.m.


Walter smiled .


Sure... but it looked like a cynical smile to me.


The 42s, 15c, 41cx, and 67/97 were all top-of-the line at the time. Each one is the best of its class, and so is still desirable. The 15c does an impressive amount in a one-line, key-per-function design, and is an amazing example of doing a lot with scarce resources.

The 11C is a basic scientific calculator with a decent programming capability. The 15C is unique in what it can do.



You modestly forgot to mention that Free42 does all of this, and faster, and more accurately thanks to the 25-digit internal precision in the Decimal version. Also, whenever, behaviour of Free42 departs from the real calculator, you fix it quickly when you learn of it.

I have been able to import piles of HP41 programs effortlessly from the Software Library. If they aren't in RAW format already, hp41uc will convert the text listing with no hassle. I can't remember the last time I keyed in a program of any substance into my real 42S.


Edited: 19 July 2007, 1:02 a.m. after one or more responses were posted



reading it again, I must admit my short post may be misunderstood. What I wanted you to ponder is to start a new thread for your question about the 15C. Unfortunately, this is called a "new topic" right here on top of this forum as you can see.

Why a new thread or topic? Because Seth started this thread asking for the merits of the 42s, as indicated by the subject line. You were the first one leaving that track immediately. So my modest proposal was you start something new like "Why is the 15C so expensive?" or whatever else may describe your intentions best, using the structures this forum offers (and attracting the 15C camp to your question).

I did not plan to attack you -- in fact I was surprised by your reaction: Thor's hammer hit me ;-) BTW, I searched the web, but was unable to find an emoticon for "cynical smile". Please help. Hope I will remember I must be *very* careful with you next time ;-)

Edited: 18 July 2007, 5:02 p.m.


Hi Les,

You modestly forgot to mention that Free42 does all of this, and faster

Thanks for banging my drum for me. ;-) Of course I wrote Free42 because I like the HP-42S so much, but then again Free42 is not a calculator per se, just a piece of software that makes certain types of hardware *act* like a calculator, which is why I usually don't mention it when people start debating the merits of various HP models.

I'm actually very happy running Free42 on my Palm Z22, which gives me an HP-42S that is fast, has a ton of memory, and bidirectional I/O. Of course a touchscreen is not the greatest keyboard, but heck, for $99 I have a nice calculator that also happens to be a fine PDA... And my real HP-42S rests safely in a drawer next to my equally unused HP-15C. :-D

- Thomas


BTW, I searched the web, but was unable to find an emoticon for "cynical smile".

I would say that a "cynical smile" would look something like a "crooked grin." So here are some suggestions:




* *

And so forth .. 8)



Well, you are correct, according with The Unofficial Smilie Dictionary http://www.charm.net/~kmarsh/smiley.html your smile was not a cynical one but a sarcastic one ;-)

Seriously, I appreciate your clarification and I apologize for coming down a bit hard on you. I see your point on starting a new topic, I still feel my comment is in the right place for what I wanted to convey, i.e. if Seth was surprised about the 42s being expensive I was more surprised about the prices paid for the 15C.

Regards, Thor

Edited: 19 July 2007, 12:29 a.m.


Hi, Mike --

Good post (as well as those of Thomas Okken and others on this topic)...

One of the best things about the HP42S is its full-spectrum support of complex number calculations. If a complex result is appropriate, it appears naturally. Try calculating the square root of -3, the arcsin of 1.5, the natural log of -5, etc. on most machines. The HP42S will return the appropriate complex domain answer.

A very good point. It should be noted that the user has a choice in the handling such calculations: Complex Result (CRES) mode will yield the primary complex-valued answer, whereas Real Result (RRES) mode will return errors. The HP-15C is similar, in which Flag 8 set corresponds to CRES mode, and Flag 8 clear corresponds to RRES mode. Gene Wright's article in Datafile indicates that the HP-35s does not have this sophistication.

The other thing I like is the ease of performing matrix operations.

These two categories of operations are far far easier on the HP42S, compared to the HP-41C or HP-15C.

I also like the matrix-related functionality of the HP-42S better than any other model (especially the RPL-based models, with all those delimiters and the cluttered Matrix Editor), but certain things about the HP-42S were done better on the HP-15C:

  1. The HP-42S allows a user to enter matrices into free RAM identfied only by a stack-level dimension-only descriptor. From there, a user can then perform calculations and operations that destroy the painstakingly-entered matrices without an UNDO to recover them, if he did not save the matrices to a named variable beforehand. The HP-15C forces the user to specify a single-letter identifier for each matrix.

  2. The lack of a name or letter identifier in the HP-42S matrix descriptor can cause confusion and erroneous results if the user is not careful. Only matrix addition is commutative, so the user's not remembering which input matrix is which, will be a problem.

On complex numbers, the HP-15C is almost as easy as the HP-42S, but a few functions and capabilities are not present. These include disassembly (RPL "C->R"), polar-mode calculations, and determinant of complex-valued matrices, among others. The HP-15C's display can show only one part of one complex-valued number at a time, compared with both parts of two numbers at greater precision with the HP-42S.

-- KS

Edited: 23 July 2007, 3:37 p.m.

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