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I bought one of these new in 1987, and used it for 30 years daily in my work as a chemical engineer in industrial R&D. When it was recently lost (or perhaps stolen), I looked at other calculator options to replace it. There are many scientific calculators available today, but none offer the combination of the required functionality, simple use, compact and lightweight form, and nearly indestructible reliability presented by the HP-11C. So, I purchased another one on ebay, and am very happy to have my calculator back. This type of HP calculator has achieved a near legendary status among those that value such items as professional tools, and for good reason.
Verified purchase: Yes
These are a great legacy RPN calculator. IF you do not know what RPN stands for, check it out with Google. Be suspect of condition of keyboard and if it is missing the badge, This is a sure sign of abuse... Buyer beware. You can get the replacement rubber pads on the back, its easy to replace them. Look for good mechanical key operation and a seller willing to take it back if it does not perform! You will get what you pay for. This was a calculator with a bad display (inconsistent), keyboard function labels are bubbling like a solvent was used on it. Great calculator, this particular one was a bad purchase.
Verified purchase: Yes
It is the 2nd one of these I now have in my possession (both in near mint condition) - as well as the HP-15C (with Original Manual) I just purchased in near mint condition (only a small minor 4 letter tag on back bottom). All work as good as new out of their box! I use one of the HP-11C's for some actual calculations and it sits next to my home desktop for quick access. As a professional structural engineer - these calculators are the very best ever made for my type of calculations done - even though much of the grunt work is now done by spreadsheet and computer analysis software.
Verified purchase: Yes | Condition: Pre-owned
In 2014 NY, a lady using HP12C, and I wondered the calculator has no = key. She told me it's RPN. (Reverse Polish Notation) I recalled RPN was an efficient input method for both programmers and users, especially its memory was very small and limited. It was kinda re-discovered or news that RPN calculators are still in use. After I came back to Japan, got to know the history of Scientific/Finacial calculator, which was developed by HP. And I have never had this HP11C but HP15C, quite same functions except Matrix or imaginary numbers. The design of the HP1xC series is absolutely sophisticated and compact as HP200LX but this one really fits in my small pocket. The button layout is wonderful, I used to have some sci. calculators and normal calculators by casio, only the good thing on casio is solar powered. I have still fx260a but I am not happy about its button layout, way too many useless keys and useful keys are behind them... HP1xC series, the layout is the work of Leonardo da Vinci. These modern days, this kind of calculators must be more sophisticated than 30 years ago and I don't see any of Casio or Sharp, even HP itself make a better product than this HP11/15C. They are cheap, not inexpensive just cheap, many bugs, unfriendly user interface, bad key touch, etc. So price doesn't matter to me, I like the way of operating this calculator and superb beauty like a fashion model. And when I look at the HP1xC, it makes me realized the long history of mathematics, physics with the abacus and slide rulers. This machine is the most shiny and brilliant moment of our pre-internet ere. I carry this item everyday in my pocket or in my bag. Only one acceptable replacement is HP32S/IIRead full review
The HP 11C calculator has stood the test of time in terms of construction and function. It is compact and full of features. It can even be programmed by the user. The keys are hinged and tactile so they do not wobble and provide positive feedback. If you can find one on eBay for less than $100, grab it or a 15C. They'll both serve you well.
Verified purchase: Yes | Condition: Pre-owned