# A curator goes to the movies: The stuff of "Hidden Figures"

By Peggy A. Kidwell

Over the past few months, I’ve read Margot Lee Shetterly’s book Hidden Figures and seen the movie with the same title. These works tell stories about the African American women who worked as human computers at Langley Field, a center for research in aeronautics and later aerospace near Hampton, Virginia. They suggest much about the place of women and African Americans in the mid-20th-century United States, the history of aeronautics and space flight, and changes in American culture—be it transportation, homes, religious organizations, or fashion. These are important matters. However, as a curator who studies historic computing devices, I’m also interested in knowing what calculating devices were available to those who worked at Langley and discovering how these objects relate to Smithsonian collections. Happily, not only Shetterly but several other historians, including Paul Ceruzzi of the National Air and Space Museum, have written learnedly on Langley and on aerospace computing.

Langley Memorial Aeronautical Laboratory (named for a Secretary of the Smithsonian Institution)—later the Langley Research Center—was founded in 1917 to carry out experimental research on the design of aircraft. Initially, engineers did their own computations and plotted the data they found. In the mid-1930s, the laboratory began to hire people to perform calculations. During World War II, as the United States mobilized for full-scale warfare, the demand for human computers skyrocketed. Those running computing projects across the United States realized that women did computations competently, accepted lower salaries than men, and also were not subject to the draft.

In the course of the 1940s, Langley hired hundreds of women and invested in computing equipment for their use. One standard tool of the time, good for rough calculations, was the handheld slide rule. On a slide rule, numbers are represented by lengths. Sliding appropriately divided scales against another, one can multiply, divide, and take powers of numbers, as well as multiply or divide by trigonometric functions. The precision of the result depends on the length of the scales—using a slide rule 20 inches long, one can get roughly three significant figures. The slide rule was invented in the 1600s and began to become common among American scientists and engineers around 1900. Some were made in the United States, and some were imported from Europe. The Smithsonian has one similar to those at Langley.

Slide rules were cheap enough to be purchased and owned by individuals. For heavy duty work, the human computers at Langley Field relied more on calculating machines. The calculating machine also was invented in Europe, and not widely used in the United States until around 1900. Individual machines cost several hundred dollars. At the time, this amount was a good chunk of an ordinary person’s annual salary. The devices could add, subtract, multiply, and divide. By the time of World War II, several American firms made and sold calculating machines. Computers at Langley used the Comptometer, the Marchant, and the Friden. Langley also had ties to the Monroe Calculating Machine Company of New Jersey. A few words will introduce each of these names.

The Comptometer was invented by Dorr E. Felt of Chicago in the mid-1880s and subsequently improved. It was best for addition and subtraction, but could be used to multiply quite easily.

The Marchant brothers began by importing machines from France, rather than making them in the United States. By the time of World War I, they had designed machines themselves and manufactured them in Oakland, California. Their company later hired Swedish-born immigrant Carl Friden, who redesigned their products to include not only an electric motor but keys rather than levers for entering numbers.

Friden went on to sell calculating machines under his own name. They not only did arithmetic, but, by the 1950s, took square roots.

Products of the Monroe Calculating Machine Company had their roots in work of 19th century American inventor Frank S. Baldwin and businessman James Monroe. During World War II, several Langley human computers consulted on a Monroe publication on solving algebraic equations with calculating machines.

Even after speedier and more powerful programmable computing devices became available, people continued to use calculating machines. Only the electronic calculators of the 1960s and 1970s displaced them entirely.

Computing at Langley continued after World War II. In 1946 the laboratory received one of the most sophisticated reliable computing devices then available, a relay calculator designed at Bell Telephone Laboratories in New York City. It was called the BTL Model V (earlier versions had been called the Model I, II, III, and IV). With about 9,000 relays and 55 types of teletype equipment, the BTL Mod V weighed around ten tons and cost about \$500,000 at the time. It was at Langley until about 1958, when it was donated to Texas Technological College. However, the truck taking it to Texas tipped over, causing serious damage, and what was left ended up being used as spare parts for a second BTL Mod V, which had been built for the U.S. Army. These details come from the article “Early Digital Computers at Bell Telephone Laboratories,” published by M.M. Irvine in 2001. Portions of this second Mod V eventually ended up in the Smithsonian collections.

The BTL Mod V, unlike calculating machines, plays no role in Hidden Figures.

Langley soon began using IBM business computers like the Card Programmed Calculator. By 1957 it acquired an IBM 704 for aeronautical research. All of these computers used vacuum tubes. In 1960 Langley acquired the transistorized IBM 7090, a computer that is featured in the movie.

These new computers required far more tending than those available today. Some people learned to write programs, that is to say lines of code that told the computer what to do. At Langley, they used FORTRAN, a programming language developed by IBM for use on its products. Computer operators typed up programs on special punched cards that then were fed into the computer. An example of an IBM 7090, as well as IBM manuals giving instructions on programming it in FORTRAN, survive at the National Museum of American History.

Peggy Aldrich Kidwell is curator of mathematics.