Vviewpoints
DOI: 10.1145/2209249.2209277
historical reflections
Alan Turing’s other
Universal Machine
ALL CoMPUTer sCienTisTs know about the Univer- sal Turing Machine, the theoretical construct the Britishgenius Alan Turing
described in his famous 1936 paper on
the Entscheidungsproblem (the halting
problem). The Turing Machine is one
of the foundation stones of theoretical computer science. Much less well
known is the practical stored program
computer he proposed after the war
in February 1946. The computer was
called the ACE—Automatic Computing Engine—a name intended to evoke
the spirit of Charles Babbage, the pioneer of computing machines in the
previous century.
Almost all post-war electronic computers were, and still are, based on the
famous EDVAC Report written by John
von Neumann in June 1945 on behalf
of the computer group at the Moore
School of Electrical Engineering at the
University of Pennsylvania. Von Neumann was very familiar with Turing’s
1936 Entscheidungsproblem paper. In
1937, Turing was a research assistant
at the Institute for Advanced Study at
Princeton University, where von Neumann was a professor of mathematics.
Beyond these known facts, however, it
is not possible to say how much influence the Turing Machine had on the
design of the EDVAC. But there is no
doubt the ACE was heavily influenced
by the EDVAC Report.
The war in Europe ended in May
1945 and the institutions of Britain
began to get back to their peacetime
the Pilot aCe, may 1950. Jim Wilkinson (center right) and Donald Davies (right).
roles. Computers were in the air and
universities at Manchester, Cam-
bridge, and elsewhere established
electronic computer projects. Out-
side the academic sphere, in Lon-
don, the National Physical Laboratory
(NPL—Britain’s equivalent of the Na-
tional Bureau of Standards) started
a mathematics division to provide a
computing service for industry. With
a staff of 40 and equipped with desk
calculating machines, punched card
equipment, and a differential analyz-
er, it was an impressive organization.
In October 1945, Turing was brought
in to establish an electronic com-
puter project. He was a department
of one, and over the next few months
he evolved the design of the ACE. His
report was formally presented to the
NPL’s executive committee in Febru-
ary 1946.
