Alan Turing and his contemporaries pdf

Alan Turing and his contemporaries

ENIAC  Construction of ENIAC (Electronic Numerical 

Integrator and Computer) started in secret in 1943 at 

the University of Pennsylvania. It was first demonstrated 

to the public in February 1946. ENIAC was a magnificent 

beast. It contained 17,468 vacuum tubes, 7,200 

semiconductor diodes and 1,500 relays, weighed nearly 

30 tons and consumed 150 kW of power. It could carry 

out 5,000 simple additions or 385 multiplications per 

second – a speed improvement of about a thousand 

times on the existing mechanical methods.

Plug-boards were used for setting up a problem. The 

ENIAC could be programmed to perform complex 

sequences of operations, which could include loops, 

branches and subroutines, but the task of taking 

a problem and mapping it on to the machine was 

complex and usually took weeks. Although primarily 

designed to compute ballistics tables for artillery, 

ENIAC could be applied to a wide range of practical 

computational tasks. It was not, however, a universal 

stored-program machine that we would now recognise  

as truly general purpose.

(in about 1948) used ENIAC for calculations associated with the devel-

opment of the hydrogen bomb.

Even before ENIAC itself had been completed the team working on 

it was producing ideas for a successor computer, to be called EDVAC, 

the Electronic Discrete Variable Automatic Computer. The team’s ideas 

addressed a challenge: how to make ENIAC more general purpose, so 

that its benefits could be more easily applied to a much wider range of 

computational tasks. The ideas were written up by John von Neumann 

in June 1945 in a 101-page document entitled First draft of a report on 

the EDVAC. By 1946 copies of this report were being distributed widely 

and were read with interest on both sides of the Atlantic. A project to 

build EDVAC was launched in 1946, but due to organisational prob-

lems the machine did not become operational until 1951.

Most importantly, however, the EDVAC Report of 1945 contained the 

first widely available account of what we would now recognise as a gen-

eral-purpose stored-program electronic digital computer. EDVAC has 

become formally known as a ‘stored-program’ computer because a sin-

gle memory was used to store both the program instructions and the 

numbers on which the program operated. The stored-program concept 

is the basis of almost all computers today. Machines that conform to the 

EDVAC pattern are also sometimes called ‘von Neumann’ computers, 

to acknowledge the influence of the report’s author.

The June 1945 EDVAC document was in fact a paper study, more 

or less complete in principle but lacking engineering detail. Once hos-

tilities in the Pacific had ceased there was an understandable desire  

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The ideas men

to consolidate the Moore School’s wartime ideas and to  

explain the details to a wider American audience. 

Accordingly, the US government funded an eight-week 

course of lectures in July–August 1946 on the ‘Theory 

and Techniques for Design of Electronic Digital Com-

puters’. Twenty-eight scientists and engineers were 

invited to attend. Amongst these were just three Eng-

lishmen: David Rees, Maurice Wilkes and Douglas 

Hartree. David Rees had worked at Bletchley Park and 

then, when the war ended, had joined the Mathematics 

Department at Manchester University. Maurice Wilkes 

had worked at TRE during the war and had returned to 

Cambridge University to resume his leading role at the 

Mathematical Laboratory (later to become the Computer 

Laboratory). Douglas Hartree, at that time Professor of 

Physics at Manchester University but soon to move to 

Cambridge, was invited to give a lecture on ‘Solution of 

problems in applied mathematics’.

The  EDVAC Report and the Moore School lectures 

were the inspiration for several groups worldwide to 

consider designing their own general-purpose electronic 

computers. Certainly Maurice Wilkes’s pioneering com-

puter design activity at Cambridge University, described 

in Chapter 3, grew out of the Moore School ideas. The 

Moore School’s activities were also of considerable 

interest to Rees’s Head of Department at Manchester  

University, 

Professor Max Newman, who had been 

at Bletchley Park during the war. What happened at  

Manchester after 1946 is explained in Chapter 4.

Although the ideas promoted by the Moore School 

were of equal interest to Alan Turing, they were to  

produce a different kind of effect upon his thinking.

THE UNIVERSAL TURING MACHINE

Alan Turing was a most remarkable man. A great  

original, quite unmoved by authority, convention or 

bureaucracy, he turned his fertile mind to many sub-

jects during his tragically short life. Though classed 

in the Scientific Hall of Fame as a mathematician 

and logician, he explored areas as diverse as artificial  

intelligence (AI) and morphogenesis (the growth and 

form of living things).

Professor Max Newman (1897–

1984) was a Cambridge 

mathematician who joined 

Bletchley Park in 1942 to work on 

cryptanalysis. He specified the 

logical design of the Colossus 

code-cracking machine. In 1945 

Newman moved to Manchester 

University, where he encouraged 

the start of a computer design 

project and promoted its use for 

investigating logical problems in 

mathematics.

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