Beginnings of a revolution - The Computing Universe: A Journey through a Revolution - page 8

Fig. 1.11 The Pilot ACE was a computer
with a distinctive flavor. Turing's design
was much more detailed than that con-
tained in von Neumann's EDVAC report
published only three months earlier.
Pilot ACE had many innovative features,
such as three address instructions,
variable-length block transfer, and bit-
level manipulation, but it was difficult to
program. This is one of the reasons why
this unique design had little impact on
the architecture of computers.

establish a viable computing laboratory in Cambridge. Wilkes recalls in his
memoirs:

In the middle of May 1946 I had a visit from L.J. Comrie who was just back
from a trip to the United States. He put in my hands a document written
by J. von Neumann on behalf of the group at the Moore School and entitled
“Draft Report on the EDVAC.” Comrie, who was spending the night at St.
John's College, obligingly let me keep it until the next morning. Now, I would
have been able to take a Xerox copy, but there were then no office copiers in
existence and so I sat up late into the night reading the report. In it, clearly
laid out, were the principles on which the development of the modern
digital computer was to be based: the stored program with the same store for
numbers and instructions, the serial execution of instructions, and the use
of binary switching circuits for computation and control. I recognized this at
once as the real thing, and from that time on never had any doubt as to the
way computer development would go. 6

Another early visitor to the Moore School was J. R. Womersley from the U.K.
National Physical Laboratory. Womersley had worked with differential analyz-
ers and was duly impressed by the performance of the ENIAC. As a result of this
visit, Womersley set about organizing a computing project at his laboratory
and hired Turing to lead the team. Turing read von Neumann's report and then
designed his own plan for a stored-program computer called ACE -Automatic
Computing Engine ( Figs. 1.11 and 1.12 ), where his use of the word engine was
a deliberate homage to Charles Babbage. The ACE design report describes the
concept for the machine in the following words:

It is intended that the setting up of the machine for new problems shall be
virtually only a matter of paper work. Besides the paper work nothing will
have to be done except to prepare a pack of Hollerith cards in accordance
with this paper work, and to pass them through a card reader connected to
the machine. There will positively be no internal alterations to be made even
if we wish suddenly to switch from calculating the energy levels of the neon
atom to the enumeration of groups of order 720. It may appear puzzling that

Fig. 1.12 The London Evening News from
November 28, 1950, reporting the speed
of the Pilot ACE computer.