Alan Turing and his contemporaries pdf

Preface

specifications and comparative performance of the principal computers introduced in 

the main text.

Simon Lavington

25 September 2011

[e-mail]

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1 

THE IDEAS MEN

Simon Lavington

SCIENCE AT WAR

The momentous events of the Second World War saw countless acts 

of bravery and sacrifice on the part of those caught up in the conflict. 

Rather less perilously, large numbers of mathematicians, scientists and 

engineers found themselves drafted to government research establish-

ments where they worked on secret projects that also contributed to 

the Allied war effort. This book is about the people who took the ideas 

and challenges of wartime research and applied them to the new and 

exciting field of electronic digital computer design. It is a complex story, 

since the modern computer did not spring from the efforts of one sin-

gle inventor or one single laboratory. In this chapter we give an over-

all sense of the people involved and the places in Britain and America 

where, by 1945, ideas for new forms of computing were beginning to 

emerge.

In Britain the secret wartime establishment that is now the most 

famous was the Government Code and Cipher School at 

Bletchley Park 

in Buckinghamshire. Bletchley Park together with its present-day suc-

cessor organisation, the Government Communications Headquarters 

(GCHQ), may be well known now but in the 1940s – and indeed right 

up to the 1970s – very few people were aware of the code-breaking 

activity that had gone on there during the war. The mathematician 

Alan Turing was perhaps the most brilliant of the team of very clever 

people recruited to work there. In the spirit of the time, let us keep the 

story of Bletchley Park hidden for the moment. We shall return to it 

after introducing examples of other scientific work that went on in Brit-

ain and America during the war.

In both countries research into radar featured prominently. The chal-

lenge was to improve the accuracy and range of detection of targets, 

for which vacuum tube (formerly called ‘thermionic valve’) technology  

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Alan Turing and his contemporaries

Bletchley Park and Colossus  This country mansion 

in Buckinghamshire was taken over by the Government 

Code and Cipher School (GCCS) in 1938 and was soon 

to become the centre for top-secret code-breaking 

during the war. When activity there was at its height the 

mansion and numerous temporary outbuildings housed 

a staff of about 9,000, of whom 80 per cent were women. 

Up to 4,000 German messages that had been encrypted 

by Enigma machines were being deciphered every day. 

Bletchley Park developed electromechanical machines 

called Bombes to help decode Enigma messages. 

From mid 1942 the Germans introduced the formidable 

Lorenz 5-bit teleprinter encryption machine for High 

Command messages.

To analyse and decipher the Lorenz messages, 

mathematicians at Bletchley Park and engineers 

from the Post Office’s Research Station at Dollis 

Hill developed the Colossus series of high-speed 

electronic digital machines. Operational from 

December 1943, these Colossus machines were of 

crucial importance to the Allied war effort. However, 

their design had little impact upon early general-

purpose computers for two reasons: firstly, their 

very existence was not made public until the 1970s; 

secondly, they were special-purpose machines with 

very little internal storage.

You can visit Bletchley Park today and see working 

replicas of a Bombe and a Colossus.

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The ideas men

Professor Douglas Hartree 

is shown here in about 1935 

operating a Brunsviga mechanical 

desk calculating machine. Hartree 

(1897–1958) was a mathematical 

physicist who specialised in 

numerical computation and 

organised computing resources 

during the Second World War. 

After the war he took the lead in 

encouraging the design and use 

of the new prototype universal 

stored-program computers for 

science and engineering.

and electronic pulse techniques were stretched to the  

limit. The Telecommunications Research Establishment 

(TRE) at Malvern, Worcestershire, became a world-class 

centre for electronics excellence, especially as applied 

to airborne radar. Research for ship-borne naval radar 

was carried out at the Admiralty Signals Establishment 

(ASE) at Haslemere and Witley in Surrey.

In 1945, as hostilities ended, senior people from 

the various British and American research establish-

ments visited each other’s organisations and exchanged 

ideas. Amongst the subjects often discussed was the 

task of carrying out the many kinds of calculations 

and simulations necessary for weapons development 

and the production of military hardware. During the 

war scientific calculations had been done on a range of  

digital and analogue machines, both large and small. 

The great majority of these calculators were mechanical 

or electromechanical. In Britain the mathematician and 

physicist 

Douglas Hartree had masterminded many of 

the more important wartime computations required by 

government research establishments. In America one 

particular research group had decided to overcome the 

shortcomings of the slow electromechanical calculators 

by introducing high-speed electronic techniques. It was 

thus that in 1945, in Pennsylvania, the age of electronic 

digital computing was dawning.

THE MOORE SCHOOL: THE CRADLE OF ELECTRONIC 

COMPUTING

A huge electronic calculator called 

ENIAC (Electronic 

Numerical Integrator and Computer) was developed 

under a US government contract at the Moore School 

of Electrical Engineering at the University of Pennsyl-

vania. The spur for ENIAC had been the need to speed 

up the process of preparing ballistic firing tables for 

artillery. Leading the development team were two aca-

demics: the electrical engineer Presper Eckert and the 

physicist John Mauchley. As the work of building the 

huge machine progressed a renowned mathematician 

from Princeton University, John von Neumann, was 

also drawn into the project. Von Neumann subsequently  

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