Hewlett-Packard HP-31E

Hewlett-Packard introduced in January 1972 with the revolutionary HP-35 the World's first pocket sized electronic calculator performing both logarithmic and trigonometric functions, not only creating a new market but luring Texas Instruments, the Inventor of the Integrated Circuit, to rethink their business model. While Texas Instruments was supplying the main components to calculator manufacturers like Bowmar for their 901B and many, many more companies, seemed selling finished products being more rewarding. The introduction of the TI-2500 Datamath in April 1972 did not challenge Hewlett-Packard, it was the SR-50 that was targeting directly the successful HP-35 and started the cat and mouse game between the companies leading to products like the HP-67 or TI-59.

Here at the Datamath Calculator Museum we call this HP-31E a member of Hewlett-Packard's "Third Generation Handheld Calculators", following the HP-21 "Second Generation Handheld Calculator" and the HP-35 "First Generation Handheld Calculators". The calculator portfolio of the 30-Series was introduced in two waves in 1978 and 1979 leading to a combined 8 members, some of them manufactured till Summer 1983:

Courtesy Rick Furr, HP Calculators by Date of Introduction

To further reduce manufacturing costs of electronic calculators, Hewlett-Packard introduced with the HP-31E and its siblings a novel approach pushing the Integrated Circuits and other electronic components with a foam pad against a flexible printed circuit board (PCB) supported by a rigid metal plate avoiding soldering. While the calculators felt sturdy with the internal metal plate where the electric joints not reliable and HP switched within a few months back to a more traditional design with a rigid PCB and the components soldered onto one side and the snap discs of the keyboard soldered to the other side. The difference in weigh is obvious, while the featured HP-31E "original design" manufactured in December 1978 clocks in at 6.3 ounces / 178 grams without batteries did we measure 5.2 ounces / 133 grams on a HP-32E "revised design" manufactured in May 1979.

Milestones of HP calculators

Hewlett-Packard (HP) introduced in 1968 the World's first desktop scientific calculator, the HP 9100A. The programmable calculator stores programs on magnetic cards and lets scientists perform complex calculations without the need to access much larger computers. It is 10 times faster than most machines at solving science and engineering problems. Advertisements for the 9100A call the device a "personal computer," one of the first documented uses of the term.

Only 4 years later, on January 4, 1972, HP makes another advance in personal computing with the HP-35, the World's first scientific handheld calculator. Small enough to fit into a shirt pocket, the powerful HP-35 makes the engineer's slide rule obsolete. With the HP-80 a similar business model was introduced in February 1, 1973. In May of 1973 the HP-45 followed before the first programmable model HP-65 was introduced in January 19, 1974 with a retail price of $795. The HP-70 was introduced in August 1974 to complement the HP-80 as lower end business calculator and it took another few months till the introduction of the HP-55 in January 1975, the last calculator in Hewlett-Packard's series of "First Generation Handheld Calculators". Early in the year 1975 the price tag of the HP-35 dropped to $195 and the calculator was discontinued soon after with the introduction of its successor HP-21, a member of the "Second Generation Handheld Calculators". The introduction of the HP-31E in May 1978 together with its siblings HP-33E and HP-38E marked with the "Third Generation of Handheld Calculators" the end of HP calculators with LED Displays before introducing the revolutionary HP-41C with its alphanumeric LC-Display in July 1979 and the everlasting HP-12C and its sibling HP-11C in September 1981.

IIn the year 1975 dozens of companies manufactured calculators with 4 functions and a selling price below $20, scientific and business calculators in the range around $100 and programmable calculators priced about $250. The slide rule was outdated and famous companies like Dennert & Pape (ARISTO), A.W. Faber-Castell and Keuffel & Esser stopped the production.

If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, December 3, 2023. No reprints without written permission.