Who Invented the Computer? The ENIAC Six

Who Invented the Computer? This is the ninth installment in our ongoing series.

In 1942 the U.S. Army had a problem: how to hit a target, miles away, with artillery fire. Since it was impossible to see what you were shooting at, muzzles of artillery pieces had to be elevated to a certain angle in order to lob the shell so that it would come down with maximum effectiveness.

Unfortunately lobbing a shell onto the heads of your enemy isn't just a matter of eyeballing the distance and blasting away. It turns out that a shell's trajectory upon leaving the muzzle is affected by all sorts of local weather conditions like humidity and barometric pressure, as well as wind speed and direction. Throw in the curvature and rotation of the Earth, and weight how many times the gun has been fired previously on top of that, and things get pretty complicated — differential calculus equations type complicated.

In order to determine the correct angle of a gun muzzle for firing, Army mathematicians tweaked variables and crunched numbers by hand. The results of all this "math-a-magicking" were recorded onto ballistic tables that gunners could refer to in "the heat of the moment." Figuring out just one ballistic equation was extremely time consuming, taking approximately 40 hours. Even with an electromechanical device like Vannevar Bush's differential analyzer, the process took 30 minutes.

The need for accurate ballistic tables became ever more acute as the U.S. industry sector flexed its production muscles, pumping out hundreds of artillery pieces a day. Lacking accurate firing computations, literally thousands of guns were not being used.

The best mathematicians available

Since most men were in uniform at that time, the Army placed a want ad in a Philadelphia newspaper seeking female university graduates who had majored in mathematics. Eventually 100 women were hired for $2,400 a year, working six days a week calculating ballistic tables by hand. The Army called these women "computers," and they did an exceptional job, but the process was still too slow.

Pentagon bigwigs decided that they needed a machine that could do the equations much faster than a human being and hired two University of Pennsylvania professors, physicist John Mauchly and engineer J. Presper Eckert, to devise a solution.

Mauchly and Eckert's team began working in July 1943 on a device they called an electronic numerical integrator and computer — ENIAC for short. When completed, ENIAC would be world's first large scale digital electronic general-purpose computer, capable of calculating a firing trajectory in a mere 30 seconds.

Constructed of black steel and containing 17,468 vacuum tubes, ENIAC was of massive proportions; 8 feet high, 3 feet thick and more than 100 feet in length. It weighed more than 30 tons and occupied three sides of a large air-cooled room.

The challenge of operating ENIAC was programing — it needed to be told what to do and how to do it. Mauchly and Eckert, perceiving the process of programming to be clerical, did what most men do when faced with an onerous task: They turned to women for help. The six best of the Army's 100 women computers were selected to flip the switches, connect the cables, and keep the vacuum tubes in working order.

The ENIAC Six

These six women, Betty Synder, Maryln Wescoff, Francis Bilas, Betty Jean Jennings, Kathleen McNulty, and Ruth Lichterman, became the first programmers in modern history. The women received no instructions on how to program ENIAC. Initially, because they lacked security clearances, they weren't even permitted to view the actual machine.

Their job was to energize circuits in specific sequences by pre-setting 1,200 10-position rotary switches. Once the switches were set and the power turned on, electronic representations of numbers would pass through the various components of the machine at pre-set times, thereby churning out accurate computations.

The "ENIAC Six" were provided large wiring and logic diagrams of ENIAC's operations and told to work out on paper the necessary programming steps. Conferring with various engineers responsible for specific parts of the device, the women would break down the differential calculus equations into simple steps for ENIAC to follow. This allowed them to program an electronic computer, accomplishing a scientific and historic first.

Eventually permitted access to the machine itself, the women figured out how to instruct it to calculate firing trajectories faster than the time it took for a shell to leave the muzzle of the gun when fired. Although the women did yeoman service, ENIAC wasn't finished in time to be much help with winning the war — the atomic bombs saw to that.

The Army did officially adopt ENIAC in 1946 and used it through 1955 for various scientific operations, including weather predictions, energy expenditure equations, and important studies involving cosmic rays, thermal ignitions, and random number generations. It even facilitated the advancement of aircraft design by calculating wind tunnel variances.

It is widely rumored however that ENIAC successfully solved a problem originating from Los Alamos in 1949: the triggering sequence for the first hydrogen bomb.

Forgotten heroes

Several of the ENIAC Six would continue working with information technology and along the way make fundamental advancements in the field of computer programming: Betty Jean Jennings went on to lead the team that converted ENIAC into one of the world's first "stored program" electronic computers. Betty Snyder made a number of impressive firsts by developing the first instruction code, the first sort routine and the first software application for computers.

Sadly, it would be more than five decades before the ENIAC women were publicly recognized for their contribution. Thanks to the efforts of a later computer programmer, Kathy Kleiman, the ladies and their work were acknowledged in 1997, when they were inducted into the Hall of Fame of Women in Technology International.

In 2014 Kleiman produced a documentary, The Computers: The Remarkable Story of the ENIAC Programmers. It's worth a watch, and can be viewed online for a nominal fee.