The Museum of HP Calculators
The Museum of HP Calculators
If you have a question that isn't answered here, try the HP Forum.
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 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."
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.)
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.
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