Within a few years of its invention in 1959, the integrated circuit (microchip)--tiny, complex electronic circuits on a single chip of silicon--had become reliable and inexpensive. The president of Texas Instruments, Patrick Haggerty, wanted to demonstrate the potentially pervasive uses of the integrated circuit, which was mostly confined to military and industrial functions. In October 1965, Haggerty challenged Jack Kilby, a TI engineer and coinventor of the microchip, to design a miniature calculator that would be as powerful as desk models but small enough to fit into a coat pocket. Kilby was a man who thrived on solving difficult technical problems. He assembled a three-man team of himself and two fellow TI engineers that produced a prototype within a year. Jerry Merryman, a self-taught electrical engineer, designed the logic circuits to fit within the power and space limitations. James Van Tassel, an expert on semiconductor components, developed a small, power-efficient keyboard for the input. Kilby found a suitable rechargeable battery. Displaying the output remained a problem. Light-emitting diode LED (light-emitting diode) technology, which became the standard for calculator display, was not yet advanced enough to use. So Kilby invented a new thermal printer with a low-power printing head that pressed the paper readout against a heated digit. Kilby, Merryman, and Van Tassel applied for a patent on their "Miniature Electronic Calculator" in 1967.
Because the pocket calculator was an entirely new device, it took some years to get it into production. TI formed a joint venture with Canon of Tokyo and placed the Pocketronic Printing Calculator on the market in the United States in 1971. It was not nearly as portable and cheap as today's models: the Pocketronic weighed 2 1/2 pounds and cost $150. But it was an immediate success. Like the other electronic pocket calculators that soon began appearing, it surprised its inventors by appealing not just to businesspeople, engineers, and scientists, but also to average consumers, who used the devices to total grocery bills, figure square footage of rooms, prepare income-tax forms, and other common mathematical tasks. Improved models soon followed. In 1972 Hewlett-Packard introduced the HP-35. The first hand-held scientific calculator, it featured LED display. Also in 1972 TI marketed the Datamath, which used a single chip and had a full-floating decimal point, LED display, and limited memory. Today, pocket calculators with a wide range of functions are available, including programmable calculators which are in effect miniature computers. More than fifty million portable calculators are now sold in the United States each year, many for less than $10. In 1975 the Smithsonian Institution made the original pocket calculator part of its permanent collection. In 1976 Keuffel & Esser, manufacturer of millions of slide rules over the years, presented its last slide rule to the Smithsonian.
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