Hewlett-Packard HP-28C Handheld Electronic Calculator

This advanced scientific calculator, to use the maker's phrase, was the first graphing handheld electronic calculator made by Hewlett-Packard. It also was the first HP calculator using algebraic expressions and the first to allow integration and differentiation. It was introduced in 1987 and sold into early 1988.
The object has a black plastic case hinged along the left edge. Opening it reveals a double keyboard. Thirty-five sloping rectangular keys are on the left side and another thirty-seven on the right. Keys on the left side have letters and symbols; keys on the right include digits, symbols for arithmetic operations, and symbols associated with trigonometry, statistics, plotting, integration, and differentiation.
Above the keyboard on the left is a list of object types (e.g. complex number), symbols used to designate that type (e.g. parenthesis for complex numbers) and examples (e.g. (123.45, 678.90) for the complex number 123.45 + 678.90i). The display on the right side shows four rows of text, indicating what number or command is stored in each of four stacks. The display also can be using to show the graph of functions. A mark above it reads: hp HEWLETT (/) PACKARD 28C.
The battery cover is on the right side. A mark on the back reads: COMPLIES WITH THE LIMITS FOR A CLASS B (/) COMPUTING DEVICE PURSUANT TO SUBPART (/) J OF PART 15OF ICC RULES (/) ATI confrome classe B 2729A04383 (/) MADE IN USA. The serial number indicates the device was made in the 29th week of 1987.
Programming for the calculator – both internally and by users – was in a programming language known as RPL (Reverse Polish Lisp or ROM-based Procedural Language), a variation on the programming language LISP.
For related documentation, see 1999.0291.02. For an example of the closely related calculator that succeeded it, the HP-28S, see 2012.0063.01. The HP28-C sold for $235.
This HP28C was used by Professor Norton Starr, who taught mathematics at Amherst College in Massachusetts.
W.A.C. Mier-Jedrzejowicz, A Guide to HP Handheld Calculators and Computers , Tustin, California: Wilson/Burnett Publishing, 1997, pp. 84–87, 133.
David G. Hicks, The Museum of HP Calculators, http://www.hpmuseum.org/, accessed July, 2014.
Yves Nievergelt, “The Chip with the College Education: the HP-28C,” The American Mathematical Monthly, vol. 94, # 9, November 1987, pp. 895–902.
Currently not on view
date made
Hewlett-Packard Company
place made
United States
Physical Description
plastic (case; keys; display cover; hinge material)
metal (circuitry material)
overall: 2 cm x 9.5 cm x 15.9 cm; 25/32 in x 3 3/4 in x 6 1/4 in
ID Number
accession number
catalog number
Credit Line
Gift of Norton Starr
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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