The Museum of HP Calculators

The Museum FAQ

If you have a question that isn't answered here, try the HP Forum.

Do you own all of these calculators?

Yes, the curator is a confirmed HP calculator fanatic and has a weakness for some mechanical calculators as well.

Did you buy them all new?

No, most were bought used. I've been buying HP calculators since 1975 but didn't think of myself as a collector until quite recently.

Is there a physical museum?

There is no publicly accessible physical display. The Web pages are the museum. A physical display is possible at some point in the future.

When was the museum established?

The museum was established in May of 1995.

Who is the curator?

David Hicks. More information is available on my personal page.

How can I contact the Curator?

Via this contact form. Requests for calculators, manuals, batteries etc. are best handled via the Museum Classified Ads where they will be seen by many collectors. General questions about calculators are best handled in the HP Forum.

Why doesn't the museum display an HP-XX?

Usually because it's "too new". I have all the small models but don't feel that recent models should be treated as "museum pieces". The cut-off date for the larger 98xx series is earlier simply because I've run out of (physical) space for them. (Also, I'm somewhat less interested in BASIC models than RPN/RPL models.)

Aren't some of the exhibits really computers?

Well yes, in fact all of them are. (See the next question.)

What's the difference between computers and calculators?

Computer is a fairly vague term meaning a processor and "some other stuff". In the case of some early personal computers "some other stuff" didn't even include memory meaning that without "options" they were entirely useless.

Long ago, calculators were built to "calculate in hardware". Sometime around the 1960's however in early attempts to design electronic calculators, people realized that designing a central processor in hardware, and then writing software to simulate a calculator was a much better idea. (Simpler logic, easier to debug, easier to add features.) This revelation, has happened elsewhere and is the basis of the "microprocessor revolution".

A modern calculator is a computer processor with built-in software (firmware) for performing certain mathematical operations, a keyboard for input, a display for output and possibly other peripherals. Thus, while all the calculators in the museum have (or contain) computers, not all computers are calculators.

People tend to call one unit a calculator and another a computer based on size, price, language spoken, capabilities etc. Manufacturers may have agendas of their own. For example, some of the early 9800 series "Calculators" were extremely powerful and spoke high level languages. However, when they were made, "Computers" were things installed and run by trained operators in controlled environments. Many companies and government agencies had special approval processes in place to buy "computers". However, "Calculators" could be purchased by individuals and individuals assumed they could operate them. (Another company called its products Programmed Data Processors - PDPs for a similar reason.) By the late 1970's however, "computers" were "in" and thus the 80's series were called "computers" rather than "calculators".

One important exception to this: HP called the HP-65 "The Personal Computer" in some literature. (It may have been the first use of the term "Personal Computer".) However, they probably felt that a handheld device was inherently non-threatening and so the term wouldn't scare anyone off. Just in case, however, the official product name that went on the purchase orders was "Programmable Pocket Calculator."

Do you know where I can find an HP-XX?

What is an HP-XX Worth?

The Collector's Corner contains prices seen recently. Buyers and sellers should realize, however, that the market is quite diverse and should not feel in any way restrained by these prices. HPs tend to be expensive at eBay and more reasonable at flea markets, forsale newsgroups etc.

What's a slide rule or calculating machine worth?

There is no price guide for these items so shop around. Prices vary greatly but tend to be much higher on the net. Straight slide rules of typical lengths are generally quite inexpensive (free-$40). Circular devices in metal casings like the Fowler tend to cost more and the cylindrical models can cost hundreds or thousands of dollars. Cardboard slide rules often designed for special purposes are generally under $5.

Calculating machines vary from free to thousands of dollars depending on model and condition. I don't have pricing data on specific models but four function calculators generally sell for much more than adding machines. Even huge classy-looking adding machines with glass sides tend to be plentiful and sell for well under $100. The cheap-looking stylus driven machines are plentiful and generally cost under $7. Curtas generally sell for $70-$700 depending on whether the seller knows how collectable they are. (See the question above for HP prices.)

Can you send me a copy of...?

Most HP calculator and software manuals are now available on CD. Items that aren't on the CD either aren't in my possession or are missing because I don't have permission to copy them. If it's not on the CD, check your local used bookstores.

Where can I get batteries and chargers?

Batteries were easily obtainable until recently. If you need new ones now, you may need to make your own or contact a battery repairer. Also, try posting an ad in the Museum Classifieds.

Where can I get manuals and accessories?

Most older manuals are available in electronic form here. For accessories or paper manuals try the sources above or try placing an advertisement in the Museum Classifieds.

Where can I get technical or repair information?

Try the repairs page or the HP Forum.

Help! My HP-10C series calculator has commas and points switched!

This is a feature that allows the calculator to display numbers correctly around the world. To toggle the feature, start with the calculator off. Press and hold the ON key, press and hold the '.' key, release the ON key then release the '.' key. It is amazing how often small children are able to find this sequence on their parent's calculators.

Help! My HP-41C series calculator has commas and points switched!

This is a feature that allows the calculator to display numbers correctly around the world. Flag 28 controls the decimal indicator. To display numbers like 1,000,000.00 press <shift> SF 28. To display numbers like: 1.000.000,00 press <shift> CF 28. If you don't want digits separated in thousands like: 1000000.00, then clear flag 28 (<shift> CF 29.)

What does a flashing asterisk mean on my HP-10C series calculator?

It means it's (finally) time to replace the batteries.

How do I set the display mode and number of digits?

Most HPs have FIX, SCI and ENG buttons. You press one of these followed by the number of digits to display. Many of the newer calculators place this feature on a MODES or DISP menu. The HP-42S is the same but expects two digits or one digit and the ENTER key after FIX, SCI or ENG. The HP-28/48 models are more purely RPN so you enter the number of digits and then select the mode.

Some models including the HP-12C, HP-10, HP-80, HP-81, some HP-30 series etc. require you to press the shift key followed by the number of digits. On the HP-80 and HP-81, 0-6 indicate fixed mode displays and 7-9 indicate scientific displays. The 12C allows scientific mode to be selected by pressing the shift key and then the . key. The number of digits is not specified in this mode. On the HP-10 pressing the shift key and then the . key enables automatic decimal mode for adding dollars and cents. In this mode, the calculator automatically places the decimal point two places from the right of any number entered.

Some calculators have a DSP key. On the HP 70, DSP 0-9 selects 0-9 digits in a fixed mode display and DSP . 0-9 selects 0-9 digits in a scientific display. The HP-65 is just the opposite with DSP . 0-9 indicating fixed and DSP 0-9 indicating scientific. The HP 67 and HP-97 use the DSP key to indicate the number of digits but also have FIX, SCI and ENG keys to set the display style. The HP-91 is similar only it doesn't have a DSP key. Instead, the number of digits is set by the shift key followed by 0-9 with the display style set by FIX, SCI or ENG.

On the HP-16C you press FLOAT 0-9 to select fixed mode display with 0-9 digits. (This may sound odd if you're not familiar with this model which also provides integer math in hexadecimal, decimal, octal and binary.) FLOAT . selects scientific mode.

How do I get my HP-15C out of Complex Mode?

Clear Flag 8. (g CF 8)

How do I use an RPN calculator?

See the RPN page.

Other questions

Try the HP Forum.

Why are calculator keypads and telephone keypads laid out differently?

Keyboards first appeared on calculators well over a century ago and I don't believe anyone knows for sure how the 9 at the top became a standard, but they were clearly set in their ways long before touch tone phones appeared. My best guess is that Felt set the de facto standard with the Comptometer 1887 and this model was so wildly successful that everyone copied it.

Older calculators were set using levers but some machines had 9 at the top and others at the bottom. (For example, compare the Burkhardt and Odhner pictures, However, if you look at all the keyboarded models, you'll see that they are consistent with current designs.)

Touch tone telephones are much more recent and according to AT&T/Bell documents, they were designed that way to be closer to dial phones which had 1, 2, 3 at the top of the dial and because testing showed that people made fewer dialing errors that way. (Which, of course, may be caused by the former reason.)

Go back to the main exhibit hall