Hewlett Packard HP-35

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The HP-35 calculator, released in 1972, was the first full-function, pocket-sized scientific calculator to perform transcendental functions (such as trigonometric, logarithmic and exponential functions). Introduced at US$395, the HP-35 was available from 1972 to 1975. It had been originally known simply as "The Calculator", but Hewlett suggested that it be called the HP-35 because it had 35 keys.

Prior to the release of this calculator, most pocket calculators could only perform the four basic operations - addition, subtraction, multiplication and division. The only option for a portable device to carry out scientific calculations was by using a slide rule. However the slide rule was quickly displaced as the HP-35 was able to perform all the functions of the slide rule to ten-digit precision instantaneously anywhere. The calculator came with a rechargeable battery pack, which gave the user 3-5 hours of continuous use from a fully-charged battery.

The HP-35 was Hewlett-Packard's first product that contained both integrated circuits and LEDs (light-emitting diodes), both of which were developed in HP Labs. However, the LED display power requirement was responsible for the HP-35's short battery life between charges — about three hours. To extend operating time and avoid wearing out the on/off slide switch, users would press the decimal point key to force the display to illuminate just a single LED junction.

Like some of HP's desktop calculators it used reverse Polish notation. The HP-35 calculated arithmetic, logarithmic, and trigonometric functions but the complete implementation used only 767 carefully chosen instructions (7670 bits). It was also the first pocket calculator with a numeric range that covered 200 decades (10+/-100).

Market studies at the time had shown no market for pocket sized calculators as they would be too expensive. In about 1970, HP co-founder Bill Hewlett challenged his co-workers to create a "shirt-pocket sized HP-9100". Thus, the first 12 HP-35 portable calculators were made as a "hack" by and for other engineers at HP. It is rumoured that the development engineer got carried away and implemented a full suite of scientific functions to satisfy requests from his co-workers. When these prototypes proved popular, HP decided to turn the HP-35 into a commercial product. The HP-35 was exactly 5.8 inches long and 3.2 inches wide. This was the size of William Hewlett's shirt pocket, hence "pocket calculator".

In the first months orders were exceeding HP's expectations as to the entire market size, which was 10,000 units per year. Introduction of the HP-35 and similar scientific calculators by Texas Instruments soon thereafter signalled the demise of the slide rule as a status symbol among science and engineering students. Slide rule holsters rapidly gave way to "electronic slide rule" holsters, and colleges began to drop slide-rule classes from their curricula. 100,000 HP-35 calculators were sold in the first year, and over 300,000 by the time it was discontinued in 1975—3½ years after its introduction.

In 1972, the year of its release, it was the first scientific calculator to fly in space (along with the HP-65 and HP-41).

In 2007 HP released the HP-35s to commemorate the 35th anniversary of the release of the original HP-35, including a limited production version with a shiny black overlay and engraving of "Celebrating 35 years".

In 2009, the IEEE, the world’s largest technical professional association, announced that it had named the HP-35 scientific calculator as an IEEE Milestone.

Our HP-35 calculator has a reference number of 1143S 3374 and is complete with manual, power supply, adapter, hard and soft case. This was very kindly donated to The Centre For Computing History by Aubrey Thyer.

Manufacturer: Hewlett Packard
Date: 1972

Other Systems Related To Hewlett Packard HP-35:

Item Manufacturer Date
Hewlett-Packard HP-71B Programmable Calculator Hewlett Packard Unknown
Hewlett-Packard HP-34C Programmable Scientific Calculator Hewlett Packard Unknown
Hewlett-Packard HP-11C Hewlett Packard Unknown
Hewlett-Packard HP-9825A Hewlett Packard 1976
Hewlett-Packard HP-9825B Hewlett Packard 1976

This exhibit has a reference ID of CH12274. Please quote this reference ID in any communication with the Centre for Computing History.


Hewlett Packard HP-35

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