- Spring 1942
- Atanasoff and Berry complete a special-purpose calculator for
solving systems of simultaneous linear equations, later called
the "ABC" ("Atanasoff-Berry Computer"). This has 60 50-bit words of memory
in the form of capacitors (with refresh circuits) mounted on two revolving
drums. The clock speed is 60 Hz, and an addition takes 1 second.
For secondary memory it uses punch cards, with the holes being burned
rather than punched in them, moved around by the user. (The punch card
system's error rate was never reduced beyond 0.001%, which wasn't good enough.)
Atanasoff then left Iowa State, and apparently lost all interest
in digital computing machines.
[You can read more about the ABC in an article in one of the issues
of Scientific American from this summer, which called it the first computer.]
- Jan 1943
- Howard H. Aiken (1900-1973) and his team at Harvard University,
Cambridge, Mass. (with backing from IBM), complete the "ASCC
Mark I" ("Automatic Sequence-Controlled Calculator Mark I"). This is the first
program-controlled calculator to be widely known: Aiken was to Zuse as Pascal
to Schickard. The machine is about 60 feet long and weighs 5 tons; it has
72 accumulators.
- Dec 1943
- Alan Turing and his team at Bletchley Park, near Cambridge, England,
complete the first version of the "Colossus". This is a secret,
special-purpose decryption machine, not exactly a calculator but close kin.
It includes 2400 tubes for logic and reads characters (optically) from 5
long paper tape loops moving at 5000 characters per second.
- Nov 1945
- John W. Mauchly (pronounced Mawkly; 1907-80) and J. Presper Eckert
(1919-) and their team at the Moore School of the University of
Pennsylvania, Philadelphia, complete the "ENIAC" ("Electronic Numerator,
Integrator, Analyzer, and Computer") for the US Army's Ballistics Research
Lab. (Too late for the war and 200% over budget -- problems that would face
Eckert and Mauchly again on later projects.)
The machine is a secret (until Feb 1946) program-controlled calculator.
Its only memory is 20 10-digit accumulators (4 were originally planned).
The accumulators and logic use vacuum tubes, 17648 of them altogether.
The machine weighs 30 tons, covers about 1000 square feet of floor, and
consumes what is either 174 kilowatts (233 horsepower) or 174 hp (130 kW).
Its clock speed is 100 kHz; it can do 5000 additions per second, 333 multip-
lications per second. It reads data from punch cards, and the program is
set up on a plugboard (considered reasonable since the same or similar
program would tend to be used for weeks at a time).
Mauchly and Eckert apply for a patent. The university disputes
this at first, but they settle. The patent is finally granted in 1964, but
is overturned in 1973, in part because of the previous work by Atanasoff.
- 1945-46
- John von Neumann (1903-1957) joins the ENIAC team and writes a
report describing the future computer eventually built as the
"EDVAC" ("Electronic Discrete Variable Automatic Computer" (!)). This
report was the first description of the design of a stored-program computer.
An early draft which fails to credit other team members such as Eckert
and Mauchly gets too-wide distribution, leading to von Neumann getting
too much credit, e.g., the term "von Neumann computer" which is derived from
this paper.
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