Hewlett-Packard HP-35 Handheld Electronic Calculator

The HP-35 was the first handheld electronic calculator to display all the functions represented on a slide rule. It has a black plastic case and a total of thirty-five square or rectangular plastic keys. These include ten digit keys, a decimal point key and a pi key, all colored tan. In addition there are four arithmetic function left of the digit keys, a relatively long enter key, a change sign key, an enter exponent key, a clear x key, and a clear key, all in blue. Additional black keys are for powers, logs to base ten, natural logs, exponents, square roots, trigonometric functions (sine, cosine, tangent and the inverses of these), simple inverses, exchange, roll down, store, and recall. Above the keys is an on-off switch. There is no hole next to the switch to indicate that the display is on, as there was in the very first HP-35 calculators. Behind the switch is a red LED display that shows results. Numbers with absolute value between one hundredth and 10 billion are given in decimal form. Smaller or larger figures appear in scientific notation, with the appropriate power of ten occupying the three rightmost digit places (two for digits, one for a sign). The negative sign for the result, if needed, is at the far left. A mark on the front edge of the calculator reads: hp HEWLETT•PACKARD.

The back of the calculator has a plug for a three-prong power adapter, a compartment for a battery pack, four rubber feet, and a sticker entitled: HEWLETT•PACKARD MODEL 35 INSTRUCTIONS. Text below the sticker reads: HEWLETT-PACKARD (/) 3.75V 500MW (/) MADE IN USA PATENT PENDING. A sticker inside the battery pack reads: HEWLETT-PACKARD (/) SER.NO. 1249A 11780. The portion 1249 of the serial number indicates that it was made in the forty-ninth week of 1972. A red sticker on the lid of the battery pack reads: CAUTION (/) USE ONLY H. P. BATTERY PACK (/) MODEL NO 82001A (/) OTHER BATTERIES MAY DAMAGE CIRCUITS. A sticker on the outside top of the calculator reads: PROPERTY OF (/) Dr. R. E. Zupko.

In addition to the calculator, the gray plastic case contains a power adapter (1991.0210.01.2) labeled in part: HEWLETT - PACKARD (/) MODEL 82002A. It also has a carrying pouch (1991.0210.1.3). For the related manual, see 1991.0210.02.

In this and a few other early HP-35 electronic calculators, entering the function 2.02 ln (e ^x) gave a result of 2 rather than 2.02. In this example, the owner chose not to have the error fixed.

The donor, Ronald E. Zupko, was an historian of weights and measures and a professor at Marquette University in Milwaukee, Wisconsin.

References:

W.A.C. Mier-Jedrzejowicz, A Guide to HP Handheld Calculators and Computers , Tustin, California: Wilson/Burnett Publishing, 1997, pp. 36–39, 132.

David G. Hicks, The Museum of HP Calculators, http://www.hpmuseum.org/, accessed July, 2014.

Thomas M. Whitney, France Rodé, and Chung C. Tung, “The ‘Powerful Pocketful’: an Electronic Calculator Challenges the Slide Rule,” Hewlett-Packard Journal, June 1972, pp. 2-9.

Accession file.

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