The Museum of HP Calculators

A Typical Late '60s Electronic Model

The first electronic calculators appeared just a few years before the HP 9100A. These machines were fairly large, typically performed the four basic functions and cost several thousand dollars when introduced, dropping to around $1000 by the late '60s. Even though they cost more than the existing mechanical calculators, they were popular because they were fast, quiet, easier to operate and needed little or no maintenance.

The Sharp model pictured below was typical of late '60s four function calculators. It used an adding machine-like logic system (it lacked + and - keys but it had two equals keys.) It had switches for setting the decimal point of both the display and the single memory. As with the HP-9100, core memory was used, but in a smaller amount due to the relative simplicity of the calculator. In the picture, you can tell that something in stored in memory by the M symbol to the right of the 16 nixie tube display. You can also tell that a multiplication is in progress because the x key is lit.
Picture of a Sharp 4 function nixie tube calculator
Display (73K)
Closeup on the Sharp's core memory>
Display (84K)
Closeup on the Sharp's nixie tube display. The display is off, and if you look closely, you can see the numbers in the tubes. (Each number has its own fully formed single filament so numbers have curves.)
Display (28K)

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