Hewlett-Packard HP-55 Programmable Handheld Electronic Calculator

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Introduced in early 1975, the HP-55 handheld electronic calculator was a less expensive alternative to the HP-65. It had no card reader or program cards, but programs of up to forty-nine steps could be entered by the user. In addition, there were eighty-six pre-programmed functions and operations.
The lower part of the keyboard includes data entry keys for ten digits, as well as decimal point, enter, change sign, enter exponent, and clear display keys. It also has keys for the four arithmetic operations. Using alternate meanings for these keys offers extensive opportunities to convert between metric and standard units, as well as entering angles as degrees, radians or grads. Pressing the "R/S" (run/stop) key in the bottom right corner begins program execution.
Above this set of keys are prefix keys (function, second function, store, recall) that are combined with one or two more keystrokes to complete a command. Further keys allow programming. The calculator also includes a digital timer.
Behind the keyboard are the on/off switch and a second switch that may be set for writing programs or for running them.
Behind the switches is a red LED display for up to ten significant digits, plus two-digit exponent and appropriate signs for both. A mark along the front edge reads: hp HEWLETT•PACKARD 55.
The back of the calculator has an outlet for a power adapter, a battery case, and a sticker that reads in part: HEWLETT-PACKARD HP-55 INSTRUCTIONS. A sticker below this reads: HEWLETT•PACKARD (/) SER. NO. 1704S 01114. The first four digits of the serial number indicate that the calculator was made in the fourth week (January) of 1977. The S signifies manufacture in Singapore.
In the cardboard box with the calculator are a battery pack with three batteries, a Hewlett-Packard 8200A battery charger and power adapter, and a leather, cloth-lined case. The calculator initially sold for $395.
For related documentation received with this calculator see 1980.0813.02, 1981.0813.03, and 1980.0813.04. For other documentation see 1982.0222.05.
W.A.C. Mier-Jedrzejowicz, A Guide to HP Handheld Calculators and Computers , Tustin, California: Wilson/Burnett Publishing, 1997, pp. 44–45, 132.
David G. Hicks, The Museum of HP Calculators, http://www.hpmuseum.org/, accessed July 2014.
[Advertisement], “Hewlett-Packard introduces another uncompromising calculator, the new HP-55 Programmable Scientific,” Electronics, vol. 48, #8, April 17, 1975, pp. 60-61.
Currently not on view
date made
Hewlett-Packard Company
place made
Physical Description
plastic (case; keys; display cover material)
leather (carrying case material)
cloth (carrying case liner material)
cardboard (box material)
metal (circuitry material)
ceramic (display circuit board material)
overall: .15 cm x .08 cm x .03 cm; 1/16 in x 1/16 in x in
ID Number
catalog number
accession number
Credit Line
Gift of Nicholas Grossman
See more items in
Medicine and Science: Computers
Handheld Electronic Calculators
Computers & Business Machines
Data Source
National Museum of American History, Kenneth E. Behring Center


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