Mark I

American efforts produced a broader achievement. Howard H. Aiken (1900-1973), a
Harvard engineer working with IBM, succeeded in producing an all-electronic
calculator by 1944.
The purpose of the computer was to create ballistic charts
for the US Navy. It was about half as long as a football field and contained
about 500 miles of wiring. The Harvard-IBM Automatic Sequence Controlled
Calculator, or Mark I for short, was a electronic relay computer. It used
electromagnetic signals to move mechanical parts.
The machine was slow (taking 3-5 seconds per calculation) and inflexible (in
that sequences of calculations could not change); but it could perform basic
arithmetic as well as more complex equations.