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Hewlett Packard HP-35

Hewlett Packard  HP-35
Hewlett Packard  HP-35 in hand

Hewlett Packard HP-35

Distinctive features: The first hand-held scientific calculator.

On April 14th 2009 Hewlett Packard was awarded the IEEE Milestone in Electrical Engineering and Computing for the HP-35 calculator for the first hand-held scientific calculator.

Technical details:
Display is scientific, 10 digits mantissa and 2 digits exponent, red LED.

Scientific, using Reverse Polish Notation (RPN) - as evidenced by the lack of an "=" key.

Main integrated circuits in this example - Mostek MK6020, MK6021, MK6022, MK6023, MK6024, which comprise an arithmetic and register chip, a control and timing chip, and three 256 x 10 bits ROMs.  This chip set was also second-sourced by AMI (American Micro-systems Inc.).

3.75v (3 x AA re-chargeable).

79 mm x 147 mm x 34 mm (3.1" x 5.8" x 1.4").

Introduced February 1972, cost $395 (about 165 GBP).

Made in U.S.A. & Singapore.

The calculator illustrated above is an early example since it has no model number on the front, just 'HewlettPackard', since this was the only hand-held calculator then marketed by Hewlett-Packard.  Later examples are labelled with the model number—'HewlettPackard 35', see below.

Hewlett Packard  HP-35

With the casing taken apart, revealing the circuit board with the integrated circuits.
The small ceramic package on the right is the MK6020 Arithmetic & Register Chip, the large ceramic package on the left is the MK6021 Control and Timing Chip, and the three cans in the middle are the MK6022, MK6023, and MK6024, all 256 x 10 bits ROM chips.  Here all chips are date-coded to late 1972.

Four HP35 Versions

The Hewlett-Packard HP-35 was modified during the time that it was produced.  Acquiring these variations is an interesting task for the admirer of this iconic calculator.  Douglas Mendez has kindly provided this photograph of HP-35 calculators, together with the serial numbers on the labels on their backs, and information about them.

From left to right:

Card HP-35 Marketing Item

Card HP35 flat in pocket

The card HP-35 flat in the shirt pocket.

The story goes  that after being shown the new HP 9100 desktop scientific calculator William Hewlett asked for a version to fit his shirt pocket[1].  This resulted in the development of the HP-35 featured on this page.

The HP-35 was a real game changer, packing the scientific functions into such a small package.  To demonstrate the small size to potential purchasers the card model illustrated here was produced as a marketing item.  As shown on the left it arrived flat in a sleeve made to look like a shirt pocket printed with the slogan 'The Shirt Pocket "Answer Machine"'.  On withdrawing the flat HP-35 from the 'pocket' a rubber band inside caused it to spring to its actual 3D shape and size, as shown below.

Card HP35

The flat card HP-35 springs to the 3D shape and size of the actual real calculator on withdrawing it from the pocket.

Rear of card HP35

The rear of the card HP-35 carries the same list of operating instructions as the actual calculator.

Interestingly, the model number at the top of the instructions is here printed as "MODEL 35A".  The first version of HP devices usually had the 'A' suffix, with later versions having suffix 'B', etc., but this was not actually applied to the hand-held calculators.

Grateful thanks to Robert Musil for supplying these photographs of this very unusual marketing item.

The press release for the award of the IEEE Milestone in Electrical Engineering and Computing for the HP-35 calculator (see below) says "Introduced in 1972, the HP-35 was the world's first handheld-sized scientific calculator.  An instant hit, the HP-35 ultimately made the slide rule, which had previously been used by generations of engineers and scientists, obsolete.

The HP-35, named for its 35 keys, was the first handheld calculator to perform transcendental functions such as trigonometric, logarithmic and exponential functions.

In the first three years after its introduction in 1972, sales of the HP-35 Scientific Calculator exceeded 300,000 units."

This was the first hand-held scientific calculator.  Previously, for their calculations, engineers and scientists would have used a slide-rule or a large desktop electronic scientific calculator.  Now they could use a pocket-sized electronic calculator, if they could afford the price or persuade their company to provide one.  Hewlett Packard calculators were very well made, and reliable, and their electronics instruments have always had a very good reputation.  Together with the high specification, this made their calculators the models of choice for many professionals.  In total, 300,000 HP-35 calculators were sold[1].

The cost of the HP-35 put it out of reach of many such as poor students, so other companies started to introduce scientific calculators with lower specifications and lower cost.  While nearly all of the other calculator manufacturers concentrated on reducing the cost of their calculators, Hewlett-Packard largely maintained the price and increased the functionality.  They launched the HP-65, the first hand-held programmable calculator, in 1974, though they did introduce their own lower specification and cost scientific calculator in the HP-21 in 1975.  Hewlett-Packard are one of the few companies to continue making calculators from the early 1970s to the present day.

 

There is a lot of interesting information available about the HP-35, including:

 

 

Hewlett Packard awarded the "IEEE Milestone in Electrical Engineering and Computing" for the HP-35 calculator

On April 14th 2009 Hewlett Packard announced that it had been awarded the prestigious "IEEE Milestone in Electrical Engineering and Computing" for the HP-35 calculator, the first hand-held scientific calculator.

Presentation

Left to right presenting the IEEE HP-35 Milestone Award are: Lewis Terman (IEEE), Dave Cochran (HP-35), Richard Gowen (IEEE).

Plaque

The press release of the award explains:

"Introduced in 1972, the HP-35 was the world's first handheld-sized scientific calculator. An instant hit, the HP-35 ultimately made the slide rule, which had previously been used by generations of engineers and scientists, obsolete.

The HP-35, named for its 35 keys, was the first handheld calculator to perform transcendental functions such as trigonometric, logarithmic and exponential functions.

In the first three years after its introduction in 1972, sales of the HP-35 Scientific Calculator exceeded 300,000 units.

An IEEE Milestone plaque recording the award will be permanently displayed at HP Labs in Palo Alto, Calif., the site where the HP-35 was originally developed."

HP 35s

July 2007: Hewlett Packard launches Retro HP 35s to Commemorate 35th Anniversary of First HP Handheld Calculator. More information on the Vintage Calculator News page.

Photograph of HP35s used with permission of HP.

See also the Hewlett Packard HP-80, the first hand-held business and financial calculator, and the Hewlett Packard HP-65, the first hand-held programmable calculator.

A Guide to HP Handheld Calculators and Computers

Revised Guide to HP Calculators Available

The fifth edition of Wlodek Mier-Jedrzejowicz's "A Guide to HP Handheld Calculators and Computers" has been published.

Reference:

  1. Mier-Jedrzejowicz, "A Guide to HP Handheld Calculators and Computers", Fifth Edition, 2007, Wilson/Barnett Publishing, ISBN: 978-1-888840-40-7, p40.

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© Text & photographs copyright Nigel Tout   2000-2021  except where noted otherwise.