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When he arrived at the Manchester Computing Machine Laboratory, Baby was working
in only a rudimentary way, and Turing rolled up his sleeves to turn it into a fully functioning
computer. The original Baby had no input mechanism apart from a bank of manual switches.^14
These were used to insert a program into memory one bit at a time—not much use for real
computing. The arrangements that Williams and Kilburn had included for output were equally
crude: the user had to try to read patterns of zeros and ones (dots and dashes) as they appeared
on what was essentially a TV screen.
Turing used codebreaking technology from Bletchley Park to get the computer working
properly, designing an input–output system based on the same punched paper tape that ran
through Colossus.^15 He also designed a programming system for the computer, and wrote the
world’s first programming manual.^16 Thanks to Turing, the first electronic universal computing
machine was open for business.
Other electronic universal computers soon followed. In 1949 came Maurice Wilkes’s EDSAC,
at the University of Cambridge Mathematical Laboratory; Jay Forrester’s Whirlwind I, at the
Massachusetts Institute of Technology; the Eckert–Mauchly Computer Corporation’s BINAC
in Philadelphia; and Trevor Pearcey’s CSIRAC (pronounced ‘sigh-rack’) at the University of
Sydney in Australia. SEAC, built in Washington, DC for the US Bureau of Standards Eastern
Division, by Sam Alexander and Ralph Slutz, ran its first program in 1950, just a few weeks
before the pilot model of ACE. Later the same year SEAC was followed by SWAC, built in Los
Angeles for the US Bureau of Standards Western Division by Harry Huskey. Von Neumann’s
‘Princeton computer’, engineered by Julian Bigelow at the Princeton Institute of Advanced
Study, began working in 1951; informally known as MANIAC, this was the most influential of
the early computers. Also in 1951, electronic stored-program computers began arriving in the
marketplace. The first were the Ferranti Mark I, based on Baby and produced by the Manchester
company Ferranti Ltd; the market-dominating UNIVAC I, produced by Eckert–Mauchly; and
LEO, based on EDSAC. In 1953, IBM manufactured the company’s first stored-program elec-
tronic computer, the 701, based on the Princeton MANIAC. Electronic computing’s rough
pioneering days were coming to an end.
Turing’s universal machine: an in-depth look
A nationwide poll in the UK in 2013 judged Turing’s universal machine of 1936 to be the most
important British innovation of the last 100 years, ahead of the World Wide Web, the discovery
of penicillin, and even the discovery of the structure of DNA.^17 Let’s take at look at the workings
of Turing’s great invention.
The universal computing machine consists of a scanner and a limitless memory-tape. The
tape, which is divided into squares, runs back and forth through the scanner. Each square might
be blank, or might contain a single symbol, for example ‘0’ or ‘1’; the scanner can view only one
square of tape, and so at most one symbol, at any given time. This tape contains not only the
data needed for the computation but also the program.
The Turing machine’s basic (or ‘atomic’) actions are very simple: the scanner contains mecha-
nisms that enable it to erase the symbol on the scanned square, to print a symbol on the scanned
square, and to move the tape to the left or right, one square at a time.
The scanner can also alter the position of a dial (or some functionally equivalent device)
that is located inside it. The function of the dial is to provide the scanner with a rudimentary