[SIGCIS-Members] “Unprogramming” the ENIAC: Lehmer Child’s Play

Brian Berg brianberg at gmail.com
Wed May 10 08:01:33 PDT 2017

A new story by John Markoff posted as a blog to the Computer History
Museum's website.  I did not find anything about this in the Thomas Haigh, *et
al.* book *ENIAC in Action* book.  Brian Berg

“Unprogramming” the ENIAC: Lehmer Child’s Play
At the dawn of the modern computing era teenager Laura Gould and her
brother Donald Lehmer were the youngest “un-programmers.” That is because
ENIAC, one of the world’s first general-purpose computers, was programmed
with an array of switches and cables. When each program had been run,
someone had to return the cables to their proper storage box to be
available for the next program. Shortly after the installation of the ENIAC
their parents, Derrick Henry Lehmer and Emma Trotskaya Lehmer, who were
well-known number theorists at the University of California at Berkeley,
were invited to use the machine for mathematical research.

Designed to aid the war effort and completed in 1945 at the Moore School of
the University of Pennsylvania by John Mauchly and J. Presper Eckert,
ENIAC, or Electronic Numerical Integrator and Computer, was a pioneering
electronic digital computer. However, it was not a stored-program computer
in the modern sense of the term. Historian David Alan Grier described it as
more like an array of electronic adding machines and arithmetic units that
were held together by a web of large electrical cables.

The machine itself, which was about one thousand times faster than the
electro-mechanical calculators of that time, occupied a large room and was
evocative of a telephone switchboard of the era, with a plugboard array
that could be rewired with cables of different lengths.

That’s where Gould and her brother came in.

As youngsters they would accompany their parents on cross-country car trips
to gather valuable research time on the machine. The ENIAC would be
programmed with plugboard-style cables that were operated in the manner of
a mechanical telephone switchboard. While traveling with their parents, a
babysitter wasn’t always available, and so the two children who were then
in their early teens, would accompany their parents for the long
programming sessions that often stretched into the evening. After the
programs ran, their job was to aid in resetting the computer by laboriously
disconnected all of the cables and placing them in boxes according to

“It was our job to strike when the program was over and put all of the
cables in their appropriate boxes sorted by lengths,” she recalled.

Neither brother nor sister remember precisely what programs their parents
were developing. It is possible that they were exploring different methods
for predicting the next prime number, but it is also conceivable that they
were involved in some aspect of classified military research.

The ENIAC had been commissioned to help the United States Army calculate
artillery trajectories. However, Donald Lehmer noted that his father was a
pacifist: “He had no interest in doing anything that would kill people. I
suspect he was thinking about prime numbers.”

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