21 October 2009
The invention: The first portable and reliable hand-held calculator
capable of performing a wide range of mathematical computations.
The people behind the invention:
Jack St. Clair Kilby (1923- ), the inventor of the
Jerry D. Merryman (1932- ), the first project manager of the
team that invented the first portable calculator
James Van Tassel (1929- ), an inventor and expert on
An Ancient Dream
In the earliest accounts of civilizations that developed number
systems to perform mathematical calculations, evidence has been
found of efforts to fashion a device that would permit people to perform
these calculations with reduced effort and increased accuracy.
The ancient Babylonians are regarded as the inventors of the first
abacus (or counting board, from the Greek abakos, meaning “board”
or “tablet”). It was originally little more than a row of shallow
grooves with pebbles or bone fragments as counters.
The next step in mechanical calculation did not occur until the
early seventeenth century. John Napier, a Scottish baron and mathematician,
originated the concept of “logarithms” as a mathematical
device to make calculating easier. This concept led to the first slide
rule, created by the English mathematician William Oughtred of
Cambridge. Oughtred’s invention consisted of two identical, circular
logarithmic scales held together and adjusted by hand. The slide
rule made it possible to perform rough but rapid multiplication and
division. Oughtred’s invention in 1623 was paralleled by the work
of a German professor,Wilhelm Schickard, who built a “calculating
clock” the same year. Because the record of Schickard’s work was
lost until 1935, however, the French mathematician Blaise Pascal
was generally thought to have built the first mechanical calculator,
the “Pascaline,” in 1645.Other versions of mechanical calculators were built in later centuries,
but none was rapid or compact enough to be useful beyond specific
laboratory or mercantile situations. Meanwhile, the dream of
such a machine continued to fascinate scientists and mathematicians.
The development that made a fast, small calculator possible did
not occur until the middle of the twentieth century, when Jack St.
Clair Kilby of Texas Instruments invented the silicon microchip (or
integrated circuit) in 1958. An integrated circuit is a tiny complex of
electronic components and their connections that is produced in or
on a small slice of semiconductor material such as silicon. Patrick
Haggerty, then president of Texas Instruments, wrote in 1964 that
“integrated electronics” would “remove limitations” that determined
the size of instruments, and he recognized that Kilby’s invention
of the microchip made possible the creation of a portable,
hand-held calculator. He challenged Kilby to put together a team to
design a calculator that would be as powerful as the large, electromechanical
models in use at the time but small enough to fit into a
coat pocket. Working with Jerry D. Merryman and James Van Tassel,
Kilby began to work on the project in October, 1965.
An Amazing Reality
At the outset, there were basically five elements that had to be designed.
These were the logic designs that enabled the machine to
perform the actual calculations, the keyboard or keypad, the power
supply, the readout display, and the outer case. Kilby recalls that
once a particular size for the unit had been determined (something
that could be easily held in the hand), project manager Merryman
was able to develop the initial logic designs in three days.Van Tassel
contributed his experience with semiconductor components to solve
the problems of packaging the integrated circuit. The display required
a thermal printer that would work on a low power source.
The machine also had to include a microencapsulated ink source so
that the paper readouts could be imprinted clearly. Then the paper
had to be advanced for the next calculation. Kilby, Merryman, and
Van Tassel filed for a patent on their work in 1967.
Although this relatively small, working prototype of the minicalculator
made obsolete the transistor-operated design of the much larger desk calculators, the cost of setting up new production lines
and the need to develop a market made it impractical to begin production
immediately. Instead, Texas Instruments and Canon of Tokyo
formed a joint venture, which led to the introduction of the
Canon Pocketronic Printing Calculator in Japan in April, 1970, and
in the United States that fall. Built entirely of Texas Instruments
parts, this four-function machine with three metal oxide semiconductor (MOS) circuits was similar to the prototype designed in 1967.
The calculator was priced at $400, weighed 740 grams, and measured
101 millimeters wide by 208 millimeters long by 49 millimeters
high. It could perform twelve-digit calculations and worked up
to four decimal places.
In September, 1972, Texas Instruments put the Datamath, its first
commercial hand-held calculator using a single MOS chip, on the
retail market. It weighed 340 grams and measured 75 millimeters
wide by 137 millimeters long by 42 millimeters high. The Datamath
was priced at $120 and included a full-floating decimal point that
could appear anywhere among the numbers on its eight-digit, lightemitting
diode (LED) display. It came with a rechargeable battery
that could also be connected to a standard alternating current (AC)
outlet. The Datamath also had the ability to conserve power while
awaiting the next keyboard entry. Finally, the machine had a built-in
limited amount of memory storage.Consequences
Prior to 1970, most calculating machines were of such dimensions
that professional mathematicians and engineers were either tied to
their desks or else carried slide rules whenever they had to be away
from their offices. By 1975, Keuffel&Esser, the largest slide rule manufacturer
in the world, was producing its last model, and mechanical
engineers found that problems that had previously taken a week
could now be solved in an hour using the new machines.
That year, the Smithsonian Institution accepted the world’s first
miniature electronic calculator for its permanent collection, noting
that it was the forerunner of more than one hundred million pocket
calculators then in use. By the 1990’s, more than fifty million portable
units were being sold each year in the United States. In general,
the electronic pocket calculator revolutionized the way in which
people related to the world of numbers.
Moreover, the portability of the hand-held calculator made it
ideal for use in remote locations, such as those a petroleum engineer
might have to explore. Its rapidity and reliability made it an indispensable
instrument for construction engineers, architects, and real
estate agents, who could figure the volume of a room and other
building dimensions almost instantly and then produce cost estimates
almost on the spot.