HP 35s: Hewlett-Packard Resurrects and Improves a Super Scientific Calculator

I have the hp35s now for 11 months - i am used to the lovely old hp32sii but it was stolen recently (you know i live in South Africa). The 35s is confusing to use - lately the "2" key started to work intermittently - i am fed-up and hope they will replace the complete calculator for me.

HP 35s is not good in automatic number system conversions.

I bought an HP-35s about a month ago and I am very satisfied with it. I even wrote a simple program to solve quadratics just to get the feel of what it is like to program this machine. The calculator layout is very similar to the old HP-41 and that is the major reason why I bought it. I also own an HP-50g, which I believe is the most powerful calculator in the planet, but the machine does not appeal to me as well as the HP-35s. Only one gripe with the machine that I have is that taking the square root of a negative number does not give you a complex number as you would expect. It works that way on the HP-50g. When you take the square root of a negative number you get the message "Sqrt(Neg)". When I wrote the quadratic equation program, I had to check for the sign of the discriminant and then branch out to a subroutine if it was negative to build the complex number myself. I find that behavior with complex numbers somwhat inconsistent and very odd. The same program in the HP-50g does not require me to check for the sign of the discriminant since the square root of a negative number gives me a complex number as expected. Overall, it is a very powerful calculator and I enjoy using it more so than the HP-50g.

In 1984 my boss at the time suggested (maybe even forced) me to buy an HP calculator as he had one and loved it. I bought the 11c and it is still going strong today with daily use. I''''''''''''''''ve only had to replace the batteries 4 times over the previous 25 years. I can only hope this calculator lasts another 25 years.

I own an HP-35S and can confirm that indeed the unit has keystroke registration issues. I had one replaced within warranty since it was missing the "4" and "ENTER" key too often to be just me mis-pressing the keys. Others at the Hpmuseum.org bulletin board have had similar problems. I am not alone with the gripe. I could reproduce the problem sometimes by pressing the key at an angle. The replacement unit isn''t as anywhere as bad but it occasionally misses keystrokes. It''s not me, it is the calc. I''ve used HP calcs since 1981. I had an HP41C (still think it''s the best calc ever built), an HP32SII (still have it, great machine), an HP48G (too complicated for what I do but still have it), an HP33S (lousy keyboard layout but keys work well), and the 35S. The 35S is the only HP calc that has given me keyboard issues. I love it''s design and the layout (for the most part), but the keyboard is not well designed.

I grew up admiring HP calculators from a distance, since I couln't afford one. Since then I've owned a few, my favorite being the 32sii, and they're mostly still available. My wife gave me a complete vintage HP-25 for Christmas, and I really like that, too. As an imbedded programmer, I wore out a 16c, the best software model ever made. Anyway, I overall like the 35s, but I don't really tax it too hard. I don't have any need for polar/rect. conversions, and if I need to program something for repetitive use, that's what my laptop (w/Excel or Mathcad, or whatever) is for. So, to me it's a nice RPN calculator that has more of the feel of the 32s series, good for getting quick arithmetic done. All I really want in a handheld, anyway.

Thanks but no thanks! I''ll stick with my 28S & 48GX so I don''t get sentimental and begin wishing HP would revert away from being a Chinese toy factory...

Thanks so much for responding to my question, even though this post is old. However, I noticed some posts were recent so I thought I might get an answer to what that recall was about. I came upon your blog while looking for feedback from HP new owners of the HP-35s as well as reviews from the experts in HP calculators. Mainly, the HP-35s was on sales for $47.99 with free shipping. Very attractive price for a powerful calculator. But I just want to be sure the product does not have annoying bugs or features before buying one. What I learned from perusing the The Museum of HP Calculators, here on your blog and elsewhere, there are certain things that can definitely make the HP-35S more desireable, if the bugs and useability are improved based on the feedback everywhere. I own a couple of HP calculators: HP48SX and HP32SII. So I can certainly relate to the build quality everyone is talking about. I do hope HP listens and starts making better calculators again. I hope because they would have earn my business. :)

Quan, more than a year ago, there was rumor of an HP 35s recall. I never saw any resolution to that. Some HP 35s users reported misaligned displays and were told that HP would exchange calculators if they were returned at the customer's expense. In addition to that, there are lots of calculator fanatics who have found some operational bugs and many more providing public wish lists of features they wish HP had included in the 35s. Mostly, they wish the 35s had the build quality of the original HP 35 while selling at 20% of the 1973 price.

I just post a comment but it didn't show up. So, if this is a duplicate post, please delete it. There was a comment about a recall. What was that recall for? Has the problem been fixed? Thanks.

Air Run Haul Away: If I understand you correctly, you are typing so fast that you are losing keystrokes. Quite possibly, you are pressing keys faster than the debounce time for the software debounce routines. If so, you have exceeded the calculator's design envelope. I've not heard of other people having this experience.

The key presses on the hp-35s are so hard with such a loud clicking noise that you would have to be dead if you are not sure if you pressed a key or not. But this design feature is all for nothing because the key press recognition is not reliable. I have been using my hp-35s for three months now and I am consistently getting wrong answers when I enter calculations quickly. I know the problem is not me, because this is not my first scientific calculator, and I have never had this reliability problem with my ti-83, ti-86, ti-89 or hp-48g. What is the point of having such loud clicking keys if the dog gone calculator does not remember all of the keys that were pressed? I really hope this is a factory defect because I like almost everything else about this calculator, and the features I like the most on this calculator are not available on any other calculator that is allowed on the PE Exam. When I get the right answers the hp-35s is very fun to use. But I have to press the keys slowly to make sure that I get the right answers. And it really takes a lot of the fun out of using an RPN calculator if you have to look at the screen while you are typing the numbers in order to catch the frequent key presses that are apparently not captured by the calculator''s operating system. "Aaarrrrrggggghhhhh!!!!!"

I just watched the fantastic video of Tom Osborne, inventor of Hp 35 and 65. ( see the right hand side bar for a link to video ) WOW. In my earlier post I mentioned programming the 65 for dec to Bin, but failed to mention it was Hexadecimal output that I wanted and got. If you like the RPN, 35's, 65, etc. do take a look at the video.

I had an Hp 45 great calculator. The power of the 35s seems enormous. More like a computer than a calculator.

Howard, I'm very sorry for your loss (the 11C and the 42s) but has someone reported you for calculator abuse yet? Take a look at www.fixthatcalc.com for possible help.

I have 2x 42S, an 11C and a 15C, but in the last week, both the 11C and one of the 42S's have died (trauma!)... my old 11C was like a part of me, it has survived 22 years, two falls of over 20 m, been hit by dust, chemicals, water, radiation and children. Am hoping to get it and the faithful 42S fixed, but don't hold out much hope. May buy a 35S as an RPN backup, just in case.

Kerby, you must have loved the HP 85 desktop machine. It only had enough power to run the CRT display or the tape drive, so when the tape spun, the display blanked.

Does this mean I don't have to buy new battries for my Sinclar Scientific? I love watching the LEDs turn off when it does a calculation! I liked my HP35 enough to get the HP45 and add the card reader with the wand.

The designer of the 33s should have been tortured first then shot...It is interesting that HP are still trying to sell that piece of s.h.i.t. I was constantly hitting wrong buttons and the action on the buttons were terrible. I had no confidence in the calculator The 35s is a much better calculator. I have confidence in the results. God I still wish they would come out with a new HP 15C

I've owned numerous HP models over the years starting with the 42e which took me to the state UIL calculator competition twice in the 80's. The 10c and 41CX got me through college. I later bought a 32sII and thought I was in heaven. After years of not needing a scientific calculator I sold my 32sII. I recently had to take the FE exam and needed a solid HP calculator for the exam, but found out the only HP models alowed are the 33s and the 35s. I bought both to try them. I agree that the designer of the 33s should have been fired or shot - it is a disgrace to the name. The 35s is another story. After using it to pass the FE, I came across a 32sII and much to my suprise, I prefer the keyboard and layout of the 35s. The buttons are larger and more spaced out than the 32s. I wish HP still made a unit with the operators on the left like the old 32e, but short of that I think the 35s comes close to being perfect. I've since bought a second 35s as a backup, because if history proves me right, HP will probably discontinue this one and replace it with an inferior model or possibly do away with RPN altogher. I hope not. I do wish HP would make another "c" type calculator like the 10c or the 11c. The keyboard layout of those was great and it fit into a shirt pocket so nicely.

I love the llok and feel of this calculator. It has the Classic Look of a professional tool yet is reasonable priced. My only beef is that mine did not come with a printed manual although the (brief) quick start guide says a free printed version is available from 1-800-HP-INVENT. I haven''t ordered it yet. I really wish HP would buck this growing trend of NOT providing full manuals except on CDROM. In any case I found the operation to be surprisingly robust. While anyone can quibble about the key layout that is just a matter of personal preference - can''t satisfy everyone! Keep in mind that this is NOT intended to be a replacbment for the 41 or 42 series. Those days are gone for now. I am quite happy with tis model for what it does. I, too, was VERY disappointed with the 33S. I hope whoever designed that keyboard was summarily fired!

a very good calculator, the look and feel is near hp15c or hp41c, two calculator i used at school, a very good calculator, and a good replacement to 15 years old hp48gx that had keyboard problems,hop hp will launch an hp50g replacement of the same quality one day.

It may sound strange that a calculator can be bought based on its looks but there is certainly beauty in this device and is one of its strong points. It looks and feels like a professional tool. I have been working with it for a few weeks now and have a few comments about its programming capabilities. Before jumping to programming I like to say that the built-in Integrate and Solve functions are excellent. It can numerically solve and integrate fairly complicated equations with great precision. This is a great feature that adds a lot of power. You can use it for instance to work Time Value of Money calculations with ease. First the good parts. The programming is robust and versatile enough. I have implemented some fairly complicated calculations such as sunrise/sunset times for a particular date or dew/bubble point for a binary mixture. For the bad side I would say that having a relatively large memory, 32K, it is a pitty that there is no prevision for interaction with a PC. You can write a lot of lines in 32 K and you will have to enter it all on its keyboard. Another important limitation is that variables can only be named using one letter ("A", "B", etc). There is a way of using 800 variables through indirect reference, so the number of the variables is not the limitation but the inability to name them other than with one letter. For somewhat complicated programs it becomes very difficult to follow track. But, all in all, I think this is an excellent device for its price tag and very happy with the price/capabilities ratio.

Looks similar to the old units from this once great manufacturer. Feels a bit like the old units as well. Very robust case comparable to the so called classics (35 to 67 models) and the 10c series from the eighties. Functionality is sufficient although complex number support could be better. Also, the vector arithmetic is limited to dimensions d<4 and therefore rather poor. The keys have the classical "HP-click" but still they feel somewhat mush due to the fact that they not only bend along their "x-axis" upon pressing (as intended) but also along the "y-axis" giving a somewhat insecure feeling typical for TI''s from the 1980''s (HP/Kinpo: fix this issue! (along with the (minor) bugs reported for this machine)). Overall speaking still one of the best "scientifics" out there on the market presently but one has to realize that quality has become a scarce commodity on that market nowadays.

Don?t waste your money!!!! It is a shame that HP has released such a ergonomically poor design, although the calculator has the look and feel of the older classic calculators; that is about the only thing you get for your money. The functionality of this calculator can be described as confusing and very poorly thought out, it is hard to believe that HP has released this model with its present flaws. As an example; simple things like numerical base conversions which should be a straight forward function using a few key strokes, will leave you wondering. However, when you try such conversion in this calculator it will leave you scratching your head for an answer and don?t bother looking for the answer in the user?s manual, because the so called ?user?s manual? has very little information about anything and it is pretty much useless.

I have two HP41cxs (non-virtual), and a HP25. For the 41s, I have the CMT HPIL digital meter, HPIL link and the HPIL floppy disk drive. Still use them at work. Will never part with them. Tom A.

I've got a 41C that I carry everyday. It's a download in my palm pilot. Too bad it doesn't support synthetic programming.

I'll keep using the HP65 I have on my desk.

If you own a 42s, there is no reason to buy this one. The 35s looks great, and is better built than recent hp models, but beware: - the keyboard has a nice feel, but does not equal the key touch of good old times. - there are *obvious* flaws in design and software that should have been corrected before production, to wit: - no builtin way to split Re and Im part of a complex number (this is a GLARING failure). - complex arithmetic is slightly better than with 32sii, with the same flaws (i.e., some functions allowed, some other not). Overall, this makes this complex support quite defective and little usable. - vector support is simply ridiculous. Again no way to split a vector nor doing something useful with it - major design failures: STO is a shifted key, as are exp, log, 10^x, ln. - Bugs of hp 33s (of which this calculator is a better-quality-build rehash) stay here (e.g. cosine bug). Don''t get me wrong, this is a very good calculator that makes for a much better 33s adding some of the good things of older models (32sII, essentially), but to compare *decently* to models 10 years old or more this would need a major face lift.

The batteries in my 42S died long ago. I started life with a $495 HP45. $100 for the polar to rectangular key was well worth it. I might buy one of these just to encourage HP to keep it up instead of giving in to the equal key. I have long believed that if kids used a simple RPN calculator at school they would never have trouble with algebra. They would learn the order of operations and how to think the problem through like a game. Typing an equation in and pressing = teaches them nothing.

I use a 41cv but it died. So I got a the new HP35S. I use about 5 programs which I assign to the top row of keys. I have one that converts a decimal number into FT Inches & sixteenth and one to do the reverse, a weight calculation formula and a simple multiplier key. Anyway the Hp 35s doesn't appear to a way to assign keys which makes it useless to me. Is there a way to assign shortcut keys to run more than one program with one key stroke like the 41CV?

I was seriously considering a 35S, but after reading some of the comments, I think that I will keep using my 42S. They do look similar and most of the keys are in similar positions, but I don't want to spend $60 on a cheap HP labeled Chinese Calculator. I would prefer to spend $100 or more on a solid reliable calculator. Maybe HP can get the problems fixed and then I might spring for one. I have been using HP calcs since my 1st in 1975, a HP25, then a 41cv, and a 42s and last a 48sx. If I'm careful, maybe the 42 and 48 will last until I retire.

Mike Gomez (above) says he got one but was disappointed with the results. It is NOT a viable replacement for the 42s. That's all I needed to know. Thanks to MG for saving me $60 and a ton of aggravation.

I just started looking at the 35s, hoping for a 42s replacement. I bought the 33s but was highly disappointed. $400+ on Ebay is not an option. The 35s keyboard LOOKS promising but I am hesitant about blowing $60 as my $50 mistake (33s) is still staring at me. It was really more like $80 because I bought a lot of programming instructions from third parties. In the meantime, try www.fixthatcalc.com I tried it and was satisfied with the results. BTW, I'm still using my 42s as I haven't found a reasonable replacement.

35 s looks great. looks similar to my 1981 model 34C. (still running OK) Have later used 11C, 42S, 48GX and 49G. My favorite is still the 42S. I think I have to buy the 35S. I am still waiting for a re-launche of the 42S; please HP. One quart of the LCD of my 42S is not showing anything. Possible to fix??

A great calculator : beautiful design, more than 800 memories; just left and rigth arrows on blue and yellow keys : is it really usefull ? may be HP will fix that for the next (and soon) issue.

I'm looking for a calculator that programs like the no longer made HP42s. Is the Hp 35s the one? Can someone let me know. mgomezcivil@hotmail.com

Unfortunately, I've been quite disappointed with the 35s. Within a few days, the faceplate popped up around the display and this unit was purchased after the recall! In my opinion, another cheap piece of crap from China! Perhaps I should test it for lead!!!

Very similar to the HP-20S, but RPN with 2 line display. Does complex numbers and vectors. Doesn't do differentiation. Does do numerical integration. Does Hexadecimal, Octal and Binary bases, and limited binary operations (boolean only, no shifts/rotates). Solver. I'll keep my HP-28C (more powerful, but bulkier and slower to use), but I'll probably retire the 20S.

It looks great, but these days, I would want a usb connection to a PC with the minimum functionally of backing up and restoring programs. A program on the pc function would be nice for serious work.

I still have a working HP 35, with case and charger. The batteries are long dead, but it runs fine on the charger. Many years back when the HP 65 was introduced, we accidentally left it exposed to a large radiation source for about 10 seconds. Every LED and decimal point was lit when we turned it on after the exposure. HP wanted it to evaluate the effects of the radiation. HP replaced it with a new one and we were much more careful with the replacement.

The HP 35s looks terrific! But it looks more like the HP 41C than it does the HP 35.

The return to a clean, classic look for the latest HP calculator. This is an awesome calculator. I ordered mine from the HP SMB online store and got it quickly. I am pleased with the calculator, the manual, and HP's service. I hope they follow the looks in the next iteration of the HP 50g. I would buy the next iteration of the HP 50 if the only change was to this same look and style.

Thanks for the tip, Jedi. I'll blog it separately.

And now HP is recalling them to correct a design flaw!

This is the best calculator to come out of HP for years. It reminds me of my old HP-15c, which I sold long ago when I was a starving grad student. The keys have the same feel I recall from the HP-15c. Plus, it is really a calculator rather than a squeezed down (and not too useful in my opinion) version of Mathematica found in the graphical series of products.

Wow! Thanks for the mini review. Anyone else?

I never thought anything could top my old 11c but this sure comes close. Many things are actually simpler and easier! What? My favorite improvement is that you can use the calculator while it is still in the case. This may not sound like much but I really like it. It keeps you from misplacing the case (something I do all the time) and it protects the back of the case from scratches. I have a near mint 12c (1987) and the only blemish is a small scratch on the back. The display is almost as good as the 11c and a vast improvement over the 33s. You can now see the decimal point without a magnifying class. The same is true for the keyboard layout. Clean and neat just like the 11c and WAY better the that confused mess that is the 33s. I never thought I would say this but the programming is better than the 11c. SHOCK! The best thing is the way the program lines are displayed. It shows the line and the program that it is associated with instead of just number, 001 in the 11c. The 35s shows A001 indicating that this line is associated with program A. I like it! Another program improvement is the way the function is displayed. It shows what the functions is, like X for times instead of the key location 20 (line 2, key 10) as in the 11c. This a big help in debugging a program. Almost as useful is the up and down caret key to move through a program. The only really dysfunctional item is the orientation of the yellow and blue arrow keys. They refer to the keyboard layout of the 33s. Doh! They should be: LEFT to RIGHT up for the yellow key and left to right DOWN! for the blue key. Maybe they will fix this on latter production runs and I will have a rarity. Ya, right. All in all I really like this machine. It may finally be time to retire the 11c and 15c to the display case. Looks like they have been replaced.

Note the big lovely enter bar. Sold.

Beautiful.