The Odyssey of the ENIAC
A Philadelphia Story
ENIAC
• Electronic Numerical Integrator And Computer
• It was completed in 1946 at the Moore School of
the University of Pennsylvania
• The two driving forces behind it were John W.
Mauchly and J. Presper Eckert
Not the first computer
• In 1839 Charles Babbage designed what he
called the “difference engine”
• It was a mechanical digital computer
• It was distinct from other computing
devices in that it could be programmed
• One of the earliest programs was written by
Ada Byron, Countess of Lovelace, who
assisted Babbage and supported him
financially
Babbage and Lovelace
Not the first electronic computer
either
• In the late 1930’s, early 1940’s John
Atanasoff and Clifford Berry built a special
purpose device from vacuum tubes (the
Atanasoff-Berry Computer ABC)
– Mauchly (of ENIAC fame) was familiar with
this work
• Around the same time, IBM, known then
for its punch-card tabulating machinery was
looking into electronic multipliers
WAR, what is it good for?
• With the war came the urgent need to
calculate
• Among other things, vast ballistic trajectory
tables (how far shells would fly) were
needed
• The Ballistic Research Laboratory was in
Aberdeen (between Philadelphia and
Baltimore)
Philadelphia
• With so many colleges and universities in
the area, Philadelphia was a good center for
these computations
• Also the Moore School (at Penn) had a
“differential analyzer”
• A differential analyzer is a collection of
gears, shafts and wires — a mechanical,
analog computer
Other Wartime Efforts
• Code breaking
• Richard Lewinsky provided the British the plans
for the ENIGMA which allowed Alan Turing and
others to break the German’s codes
• To break a harder code, Turing, T.H. Flowers and
M.H.A. Newman built an electronic decoder from
vacuum tubes: COLOSSUS
• Churchill and the Conventry bombing
Konrad Zuse
• built several versions of his computers, known as
Z1 through Z4
• they were digital and partly electronic, partly
mechanical (more and more electronic as he
progressed)
• used his computers for aerodynamic calculations
• (my main source on Zuse is Zuse)
Meanwhile back in Philadelphia
• The backlog of ballistic computations was
growing
• For example, the ground in North Africa
was softer than that in Aberdeen and thus
the tables were off and needed recalculating
WACs (poetic)
• Most of this army of calculators were
women
• Previously the Moore School had been all
male
• But they now brought in many women, and
this number was supplemented by members
of the Army’s Women’s Auxiliary Corps
(WAC)
The Moore School Players
• John W. Mauchly (overall visionary)
• J. Presper Eckert (genius with
electronics)
• John Grist Brainerd (research director
of the Moore School)
• Herman Goldstine (liaison to
Aberdeen)
Conversations
• In ongoing conversations, Mauchly and
Eckert discussed the computing problems
• Eckert, despite his youth, has vast
experience with electronics, playing with
radios and
• even television from an early age
• Eckert convinced Mauchly that vacuum
tubes would work
• organ example
The lost memo
• “Purely mechanical … devices can be
devised to expedite the work. However, a
great gain in speed … can be obtained if the
devices … employ electronic means …,
because the speed of these devices can be
made very much higher than that of any
mechanical device.”
• The memo was filed away or lost, anyway
nothing happened for about six months
A Brief History of Tubes
• It started with an effect Thomas Edison noticed
while experimenting with light bulbs
• John Ambrose Fleming discovered that one could
exploit the effect to detect radio waves and
convert them to electricity, but the signal was too
small
• Lee de Forest added to the device, making the
triode; Edwin Armstrong pointed out it could be
used to amplify signals
Some Skepticism
• compared to a differential analyzer
– digital instead of analog
– electronic instead of mechanical
• tubes had bad reputation for blowing
• MIT crowd opposed
“Give them the money”
• they played down the differences to get the
proposal past the skeptics
• they probably only received the backing
because of the desperate need at the time
• Thorstein Veblen, a famous economist,
influenced the committee to give them the
money
This is a test
• The ENIAC consisted of 17,480 tubes
operating at 100,000 pulse per second
• In May of 1944, the ENIAC passed the two
accumulator test, a trivial mathematical
operations, but an amazing feat of
engineering
• Harold Pender, the dean of the Moore
School, expressed “moderate optimism”
ENIAC’s debut
• By the time ENIAC was ready, the war was
over
• ENIAC’s first real computations were not
on shell trajectories but on thermonuclear
chain reactions
• ENIAC’s formal dedication was in Feb.
1946
Programming the ENIAC
• One drawback to the ENIAC was the way it
was programmed — with wires
• A new program required rewiring
• Mauchly, Eckert and John von Neumann
discussed designs of future computers (like
EDVAC) in which the programs
(instructions) would be stored in the
computer’s memory
• The bug story
Early Programmers
Going into business for
themselves
• Mauchly and Eckert had a dispute with the
university of the patent
• Soon after they left and went into business
for themselves
• They started building the UNIVAC (The
Universal Automatic Computer)
• Computers were huge and expensive
• Skeptics said there were too few customers
The first customer
• The government, in particular, the Census
Bureau, was the first customer
• The Census Bureau has had to deal with the
problem of collecting and processing vast
amounts of information long before the
“information age”
• They played a role in the making of IBM
near the turn of the century (Herman
Hollerith)
Remington Steal
• The fledgling Eckert-Mauchly Computer
Corporation had underestimated the project
and were seriously strapped for cash
• They were bought by Remington Rand
(maker of type writers)
• They became Sperry Rand Corporation
• And finally UNISYS
References:
• Some URL’s
– http://homepage.seas.upenn.edu/~museum/
– http://www.library.upenn.edu/special/gallery/mauchly/jwmi
ntro.html
– http://www.si.edu/resource.tours/comphist/eckert.htm#tc
• Some books
– Engines of the Mind, Joel Shurkin 1984
– Computer: A History of the Information Machine, M.
Campbell-Kelly and W. Aspray