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>> SPEAKER: So, we're in
the Harvard science

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center, which is the crossroads
of the Harvard campus.

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A lot of the science departments have
their classrooms and offices in here.

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What's behind us here
is the Mark I computer,

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which was an early
electromechanical computer.

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>> So the Mark I computer
is here at Harvard

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because Howard Hathaway Aiken, who was
the person who conceived and designed

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the machine, in collaboration
with IBM engineers,

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was a Harvard professor
of applied mathematics.

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And he wanted to relieve the labor
of solving numerical equations

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by mechanical calculation that
was done on pencil and paper.

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And what we have here is
actually only a chunk of it.

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It was 51 feet long when
it was all in one piece.

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>> It could do three additions per second.

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A multiplication took six seconds.

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And a division took 15 seconds.

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So, this was a huge advance over
doing things with pencil and paper,

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but it was slow work.

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>> And keeping the machine
going all the time

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was a major feat of electromechanical
engineering expertise.

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It was used for ballistics
calculations, for calculating

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the trajectory of missiles.

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And it was also used for a little bit
of the calculation in the Manhattan

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project for determining the right
parameters for the atomic bomb.

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What you see here are paper tape drives.

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>> So, the program was punched in
paper tape and was on a loop.

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What you see there are
registers that would

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correspond to the stored memory of the
machine, which was only used for data.

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The program itself was fixed.

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These electric typewriters
were used to print the output.

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>> These dials, which
have 10 positions, are

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where you would insert the constant.

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So, the program was fixed on paper tape.

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And if you had a constant,
like you have in C code--

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you set some variable equal to a 47
at the beginning of your program--

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this is the equivalent here.

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You would dial in the number 47
on these using these registers.

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The computational equivalent
of this is much less

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than the smallest wrist watch
computer that is now being produced.