56 | 6 TURING’S GREAT INVENTION
Frankel explained that:
he firmly emphasized to me, and to others I am sure, that the fundamental conception is owing
to Turing.
I have more to say about Turing’s influence on von Neumann in Chapter 20, where I also
describe von Neumann’s influence on the design of the Manchester Baby.
So von Neumann set out the electronic basis for a practical version of the universal Turing
machine, with considerable assistance on the engineering side from his associates Presper
Eckert and John Mauchly. In von Neumann’s design the picturesque ‘scanner’ and ‘memory-
tape’ of Turing’s 1936 machine were replaced with electronic equipment, and he also replaced
Turing’s pioneering programming code with what he later described as a ‘practical’ code for
high-speed computing.^26 Von Neumann’s design went on to become an industry standard, so
although he was not the father of the computer, he was certainly one of the founding fathers of
the modern computer age. Yet among his many contributions to the development of the com-
puter, perhaps the greatest of all was simply informing America’s electronic engineers about
Turing’s concept of the stored-program universal computer.
During 1945, hard on the heels of von Neumann’s groundbreaking paper reporting his (and
Eckert and Mauchly’s) design, Turing had designed his own electronic version of his universal
machine, ACE.^27 This was radically different from von Neumann’s design (Chapters 21 and 22
describe Turing’s design in detail). Turing sacrificed everything to speed, launching a 1940s
version of what today’s computer architects call RISC (reduced instruction set computing). In
1947 he gave a clear statement of the connection, as he saw it, between the universal computing
machine of 1936 and the electronic stored-program universal digital computer:^28
Some years ago I was researching on what might now be described as an investigation of the
theoretical possibilities and limitations of digital computing machines. I considered a type of
machine which had a central mechanism, and an infinite memory which was contained on an
infinite tape . . . [D]igital computing machines . . . are in fact practical versions of the universal
machine. There is a certain central pool of electronic equipment, and a large memory, [and] the
appropriate instructions for the computing process involved are stored in the memory.
Returning to Moshe Vardi’s efforts to refute the claim that Turing invented the stored-
program concept, Vardi states (defending von Neumann’s corner) that ‘we should not confuse
a mathematical idea with an engineering design’. So at best Turing deserves the credit for an
abstract mathematical idea? Not so fast. Vardi is ignoring the fact that some inventions belong
equally to the realms of mathematics and engineering. The universal Turing machine was one
such, and this is part of its brilliance.
What Turing described in 1936 was not an abstract mathematical notion, but a solid three-
dimensional machine containing (as he said) wheels, levers, and paper tape; and the cardinal
problem in the pioneering years of electronic computing was in effect just this: how best to build
practical electronic forms of the universal Turing machine?