The HP-35

1972 · Scientific Pocket Calculator · Work 938 of 1,871

A drawing office in an engineering firm in California, on a tilted drawing board a white sheet with fine pencil lines of a machine part, a pale wooden slide rule with plain smooth scales pushed aside to the edge, in front a flat black hand-held calculator fifteen centimetres long in a thin metal frame, at the top a long narrow dark red window with a soft red glow, below it rows of small black keys, blue keys and tan keys, every key plain smooth and unmarked, a hand in a white shirt sleeve with a pencil between two fingers pressing a blue key, fluorescent light from above.

What it was used for
Hewlett-Packard introduced the HP-35 scientific pocket calculator in January 1972 at 395 dollars. It worked in reverse Polish notation with 14-digit registers of 56 bits, showed 10 digits and covered the range from 10 to the minus 99 to 10 to the 99 with automatic decimal point placement. The clock ran at 200 kHz and a transcendental function was computed within a second. The battery lasted 3 to 5 hours of continuous use. The machine measured 5.8 × 3.2 × 1.3 inches and weighed 8.7 ounces; the display was made of LEDs with moulded lenses.
What was new
IEEE Milestone plaque no. 82, dedicated on 14 April 2009, calls the HP-35 the first handheld calculator to perform transcendental functions, that is trigonometric, logarithmic and exponential ones. PMOS technology made it possible, bipolar circuits being too power-hungry and too large. The barb is in HP's own record: the market study Bill Hewlett commissioned advised against the project and forecast at best about 1,000 units a month. Hewlett built it anyway. After introduction some 10,000 units a month were sold, and more than 300,000 before it was discontinued in 1975.

What the sources leave open: Price and sales figures come from the HP Memory Project: the price from a quotation of John Minck (Inside HP Narrative), the figures from the page's own text; Bill Terry (the ORIGINS video) attests there only the discouraging market study; the technical data come from the IEEE Milestone page, which gives no price. The well-known replacement campaign over a calculation error appears in neither source and is left out here.

Connections

Every connection names its kind. “Forerunner” on its own would be a claim.

  1. Follows fromThe HP 9100A1968The IEEE Milestone for the HP-35 names the HP-9100 desktop machine as its starting point: company president Bill Hewlett wanted the same capability in his shirt pocket. Every few months he walked into the corporate labs and asked how the team was doing.Source: Milestones: Development of the HP-35, the First Handheld Scientific Calculator, 1972 (IEEE, ETHW)

Further reading