This prototype handheld electronic calculator was built in the Semiconductor Research and Development Laboratory at Texas Instruments in Dallas, Texas, by a team led by Jack Kilby (1923–2005), co-inventor of the integrated circuit. By the mid-1960s, TI was building microchips for industrial and military applications. The company president, Pat Haggerty, sought a consumer product that would use chips, just as earlier TI transistors had found wide use in transistor radios. Haggerty proposed a variety of possible products, and Kilby and his colleagues settled on making a small electronic calculator. TI had given an earlier development program the code name Project MIT. The calculator work, also confidential, was dubbed Project Cal Tech.
Machines that performed basic arithmetic had sold from the mid-19th century, for use in business and government. Desktop electronic calculators with vacuum tubes sold from 1961, and with transistors from 1964. Kilby envisioned something much smaller that would be roughly the size of a book. This required a smaller keyboard, a new form of display, a portable power supply, and a new memory and central processor. Kilby assigned design of the keyboard to James Van Tassel, and gave work on the memory and processor to Jerry Merryman. He took responsibility for the output and power supply himself.
By September 1967 Kilby, Merryman, and Van Tassel had made enough progress to apply for a patent. The submitted a revised patent in May 1971 and a further revision in December 1972. This final application received U.S. Patent No. 3,819,921 on June 25, 1974.
The prototype resembles the “miniature electronic calculator” shown in the patent drawings. It has a metal case painted black and an array of seventeen keys and a zero bar. In addition to nine digit keys, there are keys for a decimal point, four arithmetic functions, clear (C), error (E), and print (P). The on/off switch is at the back right and a thermal printer with a thin strip of paper at the back left. The power supply plugs into the back of the calculator and into the wall.
An inscription on the front of the calculator reads: THE FIRST CAL TECH (/) PRESENTED TO P. E. HAGGERTY (/) MARCH 29, 1967.
Depressing a button on the front edge of the machine releases the cover and reveals an intricate “integrated circuit array” (to use the terminology of the patent description) and three chips. The array contained four integrated circuits, each the size of a wafer usually made with several chips on it.
Further refinement of the Cal Tech led to the commercial Pocketronic calculator, introduced by Canon in Japan in 1970 and in the United States in 1971. Texas Instruments began selling calculators under its own name in 1972.
Kathy B. Hamrick, “The History of the Hand-Held Electronic Calculator,” American Mathematical Monthly, 102, October 1996, pp. 633–639.
Jack Kilby, Oral History with Arthur L. Norberg, June 21, 1984, Charles Babbage Institute, University of Minnesota, Minneapolis, Minnesota. A transcript is available online. Accessed June 18, 2015.
T. R. Reid, The Chip: How Two Americans Invented the Microchip and Launched a Revolution, New York: Simon & Schuster, 1985.
Jeffrey Zygmont, Microchip: An Idea, Its Genesis, and the Revolution It Created, Cambridge, MA: Perseus Publishing, 2003.
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