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# Calculators: A Pocket-Sized Revolution

## Overview

The invention of the electronic pocket calculator in the 1960s ignited a world-wide microelectronics revolution. Hand-held calculating machines, portable and accurate, subsequently became valuable fixtures in science, engineering, business, and education.

## Background

Calculating machines date back to ancient Babylonian devices used to perform rote mathematical operations. Although many hand-crank and machine-type devices existed (the venerable keypunch cash register is such a mechanical calculator), prior to the 1960s, calculating machines were universally heavy, cumbersome, and expensive. The more sophisticated models—those able to perform more than just fundamental mathematical operations—were available only to government, the military, and a few large businesses. Although producing accurate results, the large, fixed-site machines required specialized training and were reserved for elaborate calculations, such as those carried out during the creation of the first atomic bombs by Project Trinity at Los Alamos during the 1940s, and required teams of men to operate the expensively maintained machines. WWII also created the desperate need to perform mathematical calculations quickly, sometimes under adverse conditions. The success or failure of a bombing run or the accuracy of artillery often depended upon the nimble fingers of soldiers struggling with mechanical-type calculators.

Prior to the introduction of the electronic pocket calculator, scientists and engineers had, since the seventeenth century, relied on the slide rule (the modern version dating back to French military officer Amedee Mannheim's 1850 design based on the operation of logarithms) to make multiplication, division, extraction of roots, and raising to powers easier to perform. Although totally supplanted by the hand-held calculator, the slide rule was an important device that, it may be fairly asserted, helped take man to the Moon. The design of the rockets and spacecraft in the pioneering days of the space race was accomplished by scientists and engineers who relied on slide rules that—instead of offering precise results to many figures—relied on the operator's experience and knowledge to make correct estimations regarding the appropriate solution to a mathematical problem.

In the mid 1960s a state-of-the-art, battery-powered, transistorized portable calculating machine might weigh more than 50 pounds (23 kg) and cost in excess of \$2,000.

In 1967, American scientists and engineers Jack St. Clair Kilby (1923- ), Jerry Merryman, and James Van Tassel revolutionized the way mathematical calculations were thereafter performed when the Texas Instruments team invented the Pocketronic—the first pocket-sized calculator. The Pocketronic was the first successful commercial usage of the monolithic integrated circuit (generally referred to as a computer microchip). The integrated circuit is an electrical circuit consisting of resistors, capacitors, diodes, and transistors, generally made from silicon, and integrated on a single silicon chip. In fact, the development of the calculator was driven by a need to find a practical commercial use for the integrated circuit. Following the success of the pocket calculator, demand for microchip technology soared throughout the world.

## Impact

Although the Pocketronic performed only the simplest of mathematical operations (enabling its users only to add, subtract, multiply, and divide), the speed and accuracy (up to 12 digit answers) of the machine proved sensational.

Kilby, whose design of the integrated circuit nosed out by few months the similar work being performed by inventors Bob Noyce (1927-1990) and Gordon Moore (1929- ), is also credited with the design for the thermal printer and more than 60 patents. Kilby was named to the National Inventors Hall of Fame and, in 1970, was awarded the National Medal of Science. In 1989, the American Society of Mechanical Engineers awarded Kilby, Merryman, and James Van Tassel a medal for their engineering feat.

In 1972, the Hewlett Packard company introduced the HP-35 pocket calculator that started a steep rise in the capacity of calculators. In addition to performing basic operations, the HP-35 enabled users to utilize advanced mathematical functions. The HP-35 was the first scientific, hand-held calculator because it carried the ability to perform a wide number of logarithmic and trigonometric functions. In addition, the HP-35 was able to store intermediate solutions and to utilize scientific notations.

The drive to create the HP-35 was supplied by Hewlett Packard co-founder William Hewlett, who was interested in developing an advance calculating machine that could fit in a shirt pocket. Almost overnight, the HP-35 became the standard in computational problem solving required in scientific, industrial, and educational settings. It is interesting to note that the first calculators (including the HP-35) were often marketed as "electronic slide rules."

In addition to advanced functions the HP-35's precision was matched only by the most sophisticated computers. Because the HP-35 could handle numbers as small as 10-99 and as large as 1099, their application to physics and engineering was unlimited. They could easily compute with far greater mathematical precision quantities far outside the range of the physical dimensions of the Cosmos.

When the HP-35 came onto the market it precipitated major changes in demand for portable calculating devices. Not only were calculators in demand by scientists and engineers but the general public clamored for the latest devices. Within a few years portable calculators replaced the use of slide rules even in high school physics and chemistry classes.

Freedom from mundane manipulations was not reserved for students, however, the HP-35 sparked interest from the business and finance communities as well. The business community soon clamored for a specialized "business computer" able to simplify often vexing financial calculations such as computing interest rates and creating amortization schedules.

On the heels of the stunning commercial success of the HP-35, the tempo of advances in calculator technology began to rise. In 1974, the first fully programmable calculator was introduced. Calculators with continuous memory functions (i.e., they maintained instructions and numbers after the units were shut off) were put on the market. In 1979 Hewlett Packard developed the first fully programmable, continuous memory, alphanumeric calculator (the HP-41 series).

The changes to education were profound and immediate. Students armed with portable calculating devices quickly and accurately performed once daunting mathematical work. Instead of being limited to highly stylized problems (i.e., problems that had whole number solutions or that contained simplified mathematical operations), teachers at all levels were, for the first time, challenged to give students more "real-world" type problems.

The introduction of the scientific calculators was not, however, without controversy. Although many teachers of mathematics viewed calculators as a tool that liberated students from pedestrian calculations, some teachers became concerned that an over-reliance on calculators was a contributing factor to sliding scores on standardized mathematics exams. Although calculators made students' work more accurate, critics of calculator usage feared a lowering of ability to perform what were once simple and rote operations. Teachers struggled with the idea that long-cherished multiplication tables might be replaced by workbooks filled with calculator exercises that ultimately became button-pushing exercises for students. During the last two decades of the twentieth century, considerable study and debate within the mathematics education community took place regarding the appropriate integration of calculator-based technology into the mathematics curriculum.

The meteoric rise in the accessibility and popularity of calculators were significantly encouraged by the low cost to the units. With mass production, prices dropped all during a time when demand, availability, and complexity of calculators rose sharply. Incredibly, Texas Instruments's Pocketronic was not even designed for mass production. In fact, Texas Instruments allowed a Japanese company (Canon, Inc. of Tokyo) to produce and market the first commercial model. Accordingly, from its quiet 1970's debut in the Japanese market, the Pocketronic's notoriety grew exponentially. The first Pocketronic, sold in the United States a few months later, carried a price tag of approximately \$400. As demand rose, however, advances in technology allowed manufacturers to actually lower costs on subsequent units. By the end the end of the twentieth century, calculators able to perform far more complex math functions than the Pocketronic sold for under \$10.

Seemingly near the limit in range of mathematical operations, calculator technology focused on lowering cost and improving displays through the use of Liquid Crystal Displays (LCDs). Power and durability were also targets for performance improvement (the batteries on the Pocketronic lasted for about four hours), and use of alternative power sources (e.g., rechargeable batteries and solar power) became important mechanisms to extend calculator utility. Calculators were made available to an increasingly diverse user group with the development of miniaturized Braille keyboards and talking displays.

During the 1980s improved calculator designs increased the range of operations to complex, multi-step algebraic, geometric, trigonometric, statistical, and calculus type functions. Hewlett Packard marketed alpha-numeric calculators with screens that displayed words and numbers that could be programmed to perform complex calculations within seconds. Even aboard the most sophisticated military aircraft, commercially available calculators became standard backup devices for navigators and pilots plotting vectors.

NASA placed the alpha-numeric successor to the HP-35, the HP-41 series, aboard the Space Shuttle spacecraft so that astronauts could, if the need arose, manually calculate the critical and exacting angles required to safely re-enter the Earth's atmosphere. By the end of the twentieth century, the hand-held pocket calculator descendants of the Pocketronic were able to rapidly graph complex equations with the power and speed once reserved to computers.

BRENDA WILMOTH LERNER

### Books

Bronowski, J. The Ascent of Man. Little Brown, 1973.

Haddock, Thomas F. A Collector's Guide to Personal Computers and Pocket Calculators. Books Americana, 1993.

Mitchell, Robert. Contemporary's Calculator Power: A Modern Approach to Math Skills. NTC/Contemporary, 1996.

Packard, David, David Kirby, and Karen Lewis, eds. The HP Way: How Bill Hewlett and I Built Our Company. Harperbusiness, 1996.

### Periodical Articles

Kim, Irene. "Functions at Your Fingerprints." Mechanical Engineering Magazine Vol. 112, No. 1 (January 1990).