Chapter 3
ENIAC: The “first” electronic
computer
In 1941, a key inventor of the ENIAC machine,
John Mauchly, was teaching physics in Ursinus
College in Philadelphia.
One day, he received an invitation from the
Moore Engineering School, UPenn, asking him
to nominate a student for a 10 week summer
program aimed at math and physics students.
He decided to enroll himself in the course.
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ABC
John, very much interested in electronic computing, already got into touch with John Atanasoff, a professor in Iowa State, who had come
up with a prototype of a digital computer with
the help of Clifford Barry, one of his students.
This machine was later referred to as “ABC”,
i.e., the “Atanasoff Barry Computer”. This
machines was declared in 1973 by a US District
Court to be the first electronic digital computing device.
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A bit more...
Conceived in 1937 and successfully tested in
1942, ABC was designed only to solve systems
of linear equations.
Thus, it is not a general purpose machine.
Moreover, its intermediate result storage mechanism, a paper card writer/reader, was unreliable.
When inventor John Vincent Atanasoff left Iowa
State for World War II assignments, work on
the machine was discontinued.
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A bit more...
On the other hand, ABC pioneered important
elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack
of a changeable, stored program distinguish it
from modern computers.
It was thus designated an IEEE Milestone in
1990.
Let’s check out how to use this machine to
solve some simple equations as we did back in
fifth/sixth grade.
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The historic background
The Pearl Harbor got hit on Dec. 7, 1941, and
the War began. Many new weapons, including new “guns”, were developed and tested in
the Army’s Aberdeen Proving Ground, 80 miles
away in Maryland.
For each new gun to hit its target, the Army
needed a new table showing the distance a shell
would travel for every firing angle between five
degrees and nearly vertical. By the middle of
1942, Moore School hired over a room full of
women mathematicians doing vital war work,
calculating ballistic tables for the military.
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Track calculation
Assume that the gun sends out bullet at the
speed of 150 ft/sec. To plot its trajectory,
assume that the gun aims at 30 degrees, we
go through the following steps:
1. break the initial velocity into its vertical and
horizontal components.
Vx = 150 × cos(30◦) = 130 ft/sec,
Vy = 150 × sin(30◦) = 75 ft/sec.
2. Choose a value for time and calculate the
horizontal distance at that time. For example,
after one section, the bullet travels horizontally
x = Vx × t = 130 ∗ 1 = 130 ft.
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3. Similarly, after one second, it travels vertically
y = Vy × t − 0.5 × g × t2
= 75(1) − 0.5 ∗ 32.2 ∗ 12 = 58.9 ft,
where g is the gravitational acceleration.
4. For each value on time, we can calculate
such a point, and we can then collect all such
points and draw the trajectory on a sheet of
graph paper.
As you can see, the concept and the calculation of trajectory is quite technical, complicated, but purely mechanical. Thus, some
powerful tool was needed.
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What is available?
The only available tools at that time were mechanic desk calculators, and it took about 40
hours to calculate one trajectory, using such a
desk calculator. Thus it took lots of time and
lots of persons to complete this task.
At that point, UPenn also had a “differential
analyzer”, one of five in the whole world. It
was about 20 feet long, a complicated but
purely mechanical device. It took this beast
about forty-five minutes to finish a trajectory
calculation.
Two people operated that machine eight hours
a day, six days a week, no vacations, except
July 4 and Christmas, during the entire war.
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The big question
Such a task, albeit important, is boring, labor
intensive, slow, but highly mechanical, as it is
just calculation based on known formulas.
The question is certainly “Could we do it better and faster?”
I bet you all know the answer now, which kicks
off the computer age.
History repeatedly shows us that “Need is the
mother of all the inventions.”
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ENIAC was the answer
After seeing this differential analyzer in operation, John Mauchly, as early as August of
1942, wrote a note to the other professors in
the Moore School, proposing to build an electronic computer that would do the work that
the differential analyzer had been doing.
In terms of processing speed, John estimated
that, if he could get a computer to operate
at 100,000 additions per second, it would take
just 10 minutes or less to calculate a firing
trajectory.
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This is the beginning of ENIAC, namely, “Electronic Numerical Integrator and Calculator”.
Originally, John’s ideas was not well received,
since people were very busy then, also thinking
the war would be over quick, so why bother?
But, when things got worse, more and bigger,
John’s idea was taken up more seriously.
Thus, it is this need for a more efficient tool
to support the war effort that was crucial to
get the ENIAC project funded.
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It is not just talking
Just as John Mauchly was a mathematician
and physicist, another person, Presper Eckert
was an electrical engineer. It is the work of this
combination that eventually made it happen.
They started the design by simulating the process where it was done by hand. Essentially,
they used some electronic device to store the
numbers in decimal, and carry out the four
basic operations, to solve the differential equations that defined the path of a shell from the
gun to its target.
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Sounds long, but...
Although such a calculation would take millions of operations, it would not take long when
the machine was to operate at the speed of
100,000 operations per second.
Mauchly figured it would take about five minutes to find out one trajectory.
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Money first
Once the design was completed, the head of
the Moore School went to the Army’s Ballistic
Research Lab for the financial support.
On April 8, 1943, they submitted a formal proposal, and a final contract was signed off on
June 5, which authorized six months of research and development of a “electronic numerical integrator and computer”at the cost
of $61,700.
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It was huge
When ENIAC was completed, it cost half a
million, occupying a room 50 feet by 30, with
18,000 vacuum tubes, 70, 000 resistors, etc..
It also generated lots of heat and the cooling
systems weighted a couple of tons.
The following machine shows how the machine
looked like.
Let’s find out more about it.
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The role played by women
The ENIAC was not completed when the War
ended. All the real computers, i.e., the human calculators, got laid off then, except five,
who were chosen to be trained as programmers, again in 10 weeks.
It is important to point out that women worked
side by side with men, and were primarily responsible for the daily running of ENIAC, which
is so clear in the video clips.
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The role played by women
Female programmers also developed improvements to ENIAC, and were honored in 1997 by
the Women in Technology Hall of Fame.
It is thus really a pity to see so few female
students are among us today in choosing CS
as their majors.
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Not impressive technically
Technically speaking, ENIAC had no internal
memory, so by programming, it really meant
plugging in and pulling out cables to form different circuitry in a switch panel.
For example, to calculate a firing table for a
particular gun, it would take days to rewire
the machine. The following figure shows the
wires and switch panels in ENIAC. Thus, at
that time, programming was even more difficult than what we are doing today.
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What did it do?
ENIAC was finally ready in November 1945,
and its first problem was to test the feasibility
of the hydrogen bomb, and its first run was
deemed successful.
It was then introduced to the public in February, 1946, as a “thinking machine”. The interest for such a machine was intense and worldwide.
The first order for an ENIAC came within 10
days from Moscow, which was not accepted.
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What happened afterwards?
Even as ENIAC was constructed, its creators,
Mauchly and Eckert thought this machine was
useless, being so big, and started to work on its
sequel, which was based on the binary system.
In such a system, every number is represented
in two digits, 0 and 1, but not in 10 digits as
we are used to, just as all the computers do.
This transition makes the computer much more
reliable and drastically cuts down the number
of components that a computer contains, since
we now only need two different parts, instead
of ten.
Although it is difficult for us to work with a binary system, it fits right in with a digital computer.
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What else?
Such a successor would also come with an internal memory to store the program and data,
which makes programming much faster.
The ENIAC creators also thought about the
potential commercial use of a computer, which
was very visionary at the moment.
On the other hand, a dispute did come up
between Mauchly and Ekcert and the Moore
School as who owned the patent of ENIAC,
and it got really ugly, when most of the participants of the project left the School.
The machine itself was eventually moved to
the basement of the Ballistic Research Lab
and was switched off for the last time on October 2, 1955. It operated 80,233 hours and
processed 5,000 arithmetic operations per second.
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von Neumann architecture
John von Neumann, a very accomplished mathematician and later a great computer scientist, was a part-time consultant to the ENIAC
project in 1944, who thought out the idea of
letting ENIAC test the feasibility of a hydrogen
bomb.
He was called “the last of the great mathematicians”, and made major contribution in
many fields of mathematics.
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John von Neumann and CS
In 1944, John von Neumann published a paper “First draft of a report on the EDVAC”,
where he laid out the basic composition of a
modern computer: input, processor, output,
control and memory. In particular, the memory should store both program and data.
We get to point out that almost all the computers that we have built since adopt this “storedprogram computer”, or “von Neumann architecture”, idea.
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What else?
John is also credited as the inventor of the
mergesort algorithm, which put a list of data
into order. It is actually one of the fastest
sortintg method.
Is estimated that about 50% of what computers do fall into the category of searching and
sorting.
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Activities
Pick a topic among the following, do some
research and write a report. We will talk about
it in a group setting.
1. Dig out some details of the ABC machine.
How did it start? Was it completed? If not,
why did Atanasoff and Barry abandon this ABC
project? What is the impact of ABC on future
development of computers?
2. Why did a dispute arise about the patent
on the ENIAC machine between Mauchly and
Ekcert and the Moore School? How did that
dispute play out?
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3. What project came up after ENIAC in Moore
School?
4. Describe John von Neumann’s contribution
in developing modern computer in layman’s
language. What other architectures exist other
than the von Neumann architecture?
5. Would von Neumann architecture continue
when the Moore’s law ceases to hold? What
is Moore’s law any way. What did Bill Gates
talk about Moore’s law over the passing summer? What kind of applications fit the non
von Neumann machine better?
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