We are concerned here with what has become the definition of a (digital) computer in an attempt to distinguish between computers and calculators i.e. a computer with the capability and capacity to operate on data according to any set of instructions (program) loaded into it.
It is appropriate to consider the level of 'Turing Completeness' in terms of
conditional processing, and the self-determination of an end-point in the
All the information below has been obtained from official archives, the majority has been doubled-checked by other documents and reports authored by the named individuals. The popular (American) version of computer history has been highly scrutinised. In the final analysis, whilst the concept of digital data processing was defined in rarified air of academia, it took a military need (see Note 1- below) coupled with some extraordinarily talented and pragmatic Englishmen to evolve into something tangible:-
|Alan Turing conceived the computer (as defined above) in 1936 whilst at Cambridge University.|
Following his election as a Fellow of King's College and attendance of
lectures by Professor Max Newman, he became interested in the application of logic and
wrote a paper: On computable numbers, with an application to the
Entscheidungsproblem, which was circulated
throughout academia in the UK and USA. The Entscheidungsproblem asks for an algorithm that will take as input a description of a formal language and a mathematical statement in the language and produce as output either "True" or "False" according to whether the statement is true or false. The algorithm need not justify its answer, nor provide a proof, so long as it is always correct. To answer such a question
required a definition of method which would be not only precise but compelling. This is what Turing supplied. He analysed what could be achieved by a person performing a methodical process, and seizing on the idea of something
performed mechanically, expressed the analysis in terms of a theoretical machine able to perform certain precisely defined elementary operations
described as symbols. He presented convincing arguments that the scope of such a machine was sufficient to encompass everything that
constituted a definite method. His virtually unrivalled capacity for
lateral parallel thinking led him to include an argument based on the transitions between 'states of mind' of a human being performing a mental process. Whilst the bulk of Alan Turing's paper promotes an abstract
mechanism for computing numbers involving interlaced order code and data,
section 6 entitled: The universal computing machine defines the
concept of general purpose computing on which all subsequent stored-program
digital computers are modelled.
Tommy Flowers of the Post Office Research Station at Dollis Hill produced the digital electronic (hardware) design employing (thermionic) valves in 1943.
His first involvement with Bletchley Park (BP) was an investigation into an electronic version of the electro-mechanical BOMBE developed as an aid to deciphering enemy messages encrypted using the ENIGMA machine. An electronic BOMBE didn't happen, but Tommy Flowers (on Alan Turing's recommendation) produced an electronic version of the counting elements of Heath Robinson, for Max Newman - see below, BP's first attempt at an automated (electro-mechanical) aid for the process of deciphering German radio traffic codenamed FISH encrypted using the LORENZ teletypewriter. The LORENZ teletypewriter incorporated a far more complex encoding system than that of the Enigma machines, making the decoding of messages virtually impossible by hand, and was used for German high-command communications. The break into FISH occurred as a result of errors on the part of a German operator in Aug 1941 (use of abbreviations and leaving-out words in the re-transmission), so that almost the same message was sent twice with the major error of using the same initial (machine) settings for the encryption. Colonel John Tiltman painstakingly deduced the plain-text of the two messages, thus exposing the nature of the encryption i.e. an additive cipher using modulo-2 addition. A few months later William (Bill) Tutte performed a truly inspired feat by deducing the design of the LORENZ machine from these messages. The Heath Robinson machine was specified by Max Newman based on the ground-breaking work of Col. John Tiltman and Bill Tutte, and C.E. Wynn-Williams designed the initial version of the counters. Tommy Flowers went on to propose an electronic version of Heath Robinson, but due to the number of electronic valves required the idea was viewed with some skepticism. Undaunted, Tommy Flowers encouraged by Max Newman invested his own time and money into the early stages of the design and build of the prototype Colossus (Colossus Mk 1 employing 1800 valves). BP cryptanalyists I.R. (Jack) Goode and Donald Mitchie specified additional functionality to assist in the codebreaking by statistical means, which led to the significantly more powerful Colossus MkII (requiring some 2,500 valves). The code-breaking capability of Colossus II's remains classified information.
Max Newman's input was the system design in terms of digital Boolean algorithms, but most importantly he got it built and working at the Government Code & Cipher School, Bletchley Park, in January 1944.
a way of carrying forward the work of Tiltman and Tutte by use of specially
designed machines, and for this purpose was given charge of a new section at
Bletchley Park, which became known as the Newmanry.
The construction of a digital computer by Newman's department at Manchester University was a key element in the establishment of the UK computer industry. Ironically, Ferranti Computer Systems Ltd involvement with the department ensured the UK had militarised Minicomputers; these, for example, where at the heart of Cold War, RN ship and submarine Action Information Organisation and Fire Control systems.
John Von Neumann put computers into the public domain in 1945.
This occurred by
virtue of his incomplete but widely circulated paper: First Draft of a
Report on the EDVAC. Had he not done so the U.S. Army and the University of Pennsylvania would have ensured nobody else got to know about them, for
years; the (initial) development of the digital computer in the UK, i.e. Colossus, was surrounded by
the Official Secrets Acts.
Design of Electronic Numerical Integrator And Computer (ENIAC) begins at the University of Pennsylvania's Moore School of Electrical Engineering. ENIAC was conceived and designed by John Mauchly and J. Presper Eckert of the University of Pennsylvania. Note the ENIAC was decimal-based and was not a stored program machine i.e. it does not satisfied the above definition of a digital computer. Until the release of information on Colossus it was claimed to be the first digital computer, having been announced to the public in Feb 1946. It could more precisely be said to be the first electronic calculator.
Colossus operational at Bletchley Park; clearly an earlier date could be declared i.e. when the prototype (Mk I) first performed to the system requirements at Post Office Research Station, Dollis Hill i.e. late November 1943.
|About June 1944||
John Von Neumann virtually takes control of the development of the ENIAC.
ENIAC inventors John Mauchly and J. Presper Eckert proposed the construction of an Electronic Discrete Variable Automatic Computer (EDVAC), and design work commenced before the ENIAC was fully operational. Unlike its predecessor the ENIAC, it was binary rather than decimal, and was a stored program machine.
|About April 1945||
Enhanced programmability Colossus Mk II (Mk III?) - this is still subject to the Official Secrets Act.
|30th June 1945||
John Von Neumann's report on the EDVAC issued publicly. It contains the first published description of the logical design of a computer using the stored-program concept, which has controversially come to be known as the von Neumann architecture. Some on the EDVAC design team contended that the stored-program concept had evolved out of meetings at the University of Pennsylvania's Moore School of Electrical Engineering predating von Neumann's activity as a consultant there. Is this argument conveniently ignoring Alan Turing's 1936 paper?
Max Newman accepted the appointment of Professor of Pure Mathematics at Manchester University, and had (ambitious) plans to build up a powerful department there.
Alan Turing having accepted an appointment at the National Physical Laboratory (NPL), Teddington produced his proposal for a stored program digital computer, the Automatic Computing Engine (ACE) and included detailed logical circuit diagrams and a cost estimate of ₤11,200. He felt that speed and size of memory were crucial and he proposed a high-speed memory with an access speed of 1 MHz. The ACE implemented subroutine calls, whereas the EDVAC did not. The ACE & the EDVAC differed greatly, as the ACE employed Abbreviated Computer Instructions, an early form of programming language.
|12th February 1946||
ENIAC unveiled at the University of Pennsylvania - was it actually working then? It was seriously modified in November 1946 and re-commissioned (finally got working!?) on 29th July 1947. Some claim that this is the true date of first operation as a general purpose computer.
|19th Feb 1946||
Turing presented a
detailed paper to the National Physical Laboratory (NPL) Executive
Committee, giving the first reasonably complete design of a stored-program
computer. However, because of the strict and long-lasting secrecy around
the Bletchley Park work, he was prohibited (because of the Official
Secrets Act) from explaining that he knew that his ideas could be
implemented in an electronic device. Although sanctioned straightaway at
high level, the project met with all sorts of obstacles; initially there
was conflict with the Post Office (PO) over use of its staff for the electronic design
and construction. The PO did eventually build some mercury delay lines for
Max Newman's proposal to build a computer (at Manchester) is accepted by the Royal Society who grant a budget of £35000. At that stage Newman expected that the American Iconoscope would become available as the storage system - as postulated by Von Neumann in his report, but it didn't work.
A contract to build the new computer was signed in April 1946 with an initial budget of US$100,000. The contract named the device the Electronic Discrete Variable Automatic Calculator (EDVAC). The final cost of EDVAC, however, was similar to the ENIAC's, at just under $500,000.
ENIAC formally accepted by the U.S. Army Ordnance Corps. ENIAC was initially designed to compute artillery firing tables, but its first use was in calculations for the hydrogen bomb.
FC Williams (out of a job, ex TRE) was appointed to the chair of electrical engineering at Manchester. Newman's idea was that it would be advantageous to exploit Williams' work on cathode-ray-tube storage, even if, as it then appeared likely, an on-site development would take longer than the Americans. Newman had no rigid ideas about hardware, and simply wanted a computer built by the most effective means possible.
|29th July 1947||
ENIAC operational in its final form i.e. working.
Newman offers Turing a post at Manchester - Turing having been side-lined at NPL, see note about security clearance - below.
|21st June 1948||
First successful run of a program on the Small-Scale Experimental Machine, known as SSEM or Manchester Baby. It could store 1024 bits on a cathode-ray-tube, enough to demonstrate the stored-program principle in working electronics, the first in the world to do so.
Alan Turing joins Max Newman at Manchester. (I believe it's fairly significant that Turing lost his security clearance in 1948 - this was an MI5
versus MI6 thing.) The salary for Turing's post came from the Royal Society grant. He was formally 'Deputy Director' of the Royal Society Computing Machine Laboratory. The grounds for appointing him to this post, as minuted on 15 October 1948, were:-
With the onset of the Cold War it became a British national priority to have computing facilities for the atomic bomb implosion calculation. A lavish new contract was rushed through to allow Ferranti to build a full-scale machine, the Ferranti Mark 1. The contract specified merely that it would be built to F.C.Williams's design. Newman's priorities for pure mathematics and science were forgotten.
Electronic Delay Storage Automatic Calculator (EDSAC computer) fully operational (with Bootstrap Loader) at University of Cambridge Mathematical Laboratory, designed by Maurice Wilkes. Initial programs (hand loaded) ran in February 1949.
A version of Turing's ACE design known as Pilot ACE operational - fastest in the world.
A second implementation of the ACE design was the MOSAIC
(Ministry of Supply Automatic Integrator and Computer). This was built by
Allen Coombs and William Chandler of PO (Dollis Hill) who had worked
with Tommy Flowers on building the ten Colossus computers. It was
installed at the Telecommunications Research Establishment (TRE) which
soon became the Royal Radar Establishment (RRE) at Malvern and ran its
first program in late 1952 or early 1953. It was used to calculate
aircraft trajectories from radar data.
Ferranti Mk 1 operational at Manchester University - the first production machine. The Ferranti Mk 1 was based on the Manchester Mk 1 (operational in April 1949), which was designed at the University of Manchester by Freddie Williams and Tom Kilburn; the Manchester Mk 1 being a development of the 'Baby' that they together with Geoff Tootill built.
RA (Tony) Brooker, from Cambridge where he worked with Wilkes on EDSAC, replaces Alan Turing in charge of the software side at Manchester. Whilst at Manchester, Brooker (having already developed in 1954 the world's first publicly available high level programming language - Mk 1 Autocode) developed the concept of a Compiler Compiler; this revolutionary idea was presented at the British Computer Society's 1960 conference, and paved the way for many high-level language developments.
EDVAC operational finally, as design rights dispute rattled-on between the designers of ENIAC and University of Pennsylvania.
Replicas of the early computers that can be seen today
A working replica of the Manchester Baby was commissioned in 1998 and may be seen in Manchester's Museum of Science & Industry.
A working replica of a Colossus has been built at The National Museum of Computing (TNMOC), by a team inspired and led by Dr A.E. (Tony) Sale*. Inaugurated in 1994, its completion was marked by the 2007 Cipher Challenge in which Colossus was pitted against modern computers (principally PCs & Laptops) in an authentic code-breaking task including the radio reception of the enciphered messages. The Cipher Challenge was also used to mark the start of a major fund-raising drive for the fledgling National Museum of Computing. The Museum is based in Bletchley Park's Block H (known during wartime as the Newmanry) and Colossus forms the centre-piece of its exhibits.
A working replica of EDSAC is to be built at TNMOC, BP; this project was announced in Jan 2011.
* Tony Sale, perhaps best known for leading the team that built a (as near as possible) replica Colossus computer, helped establish the Computer Conservation Society, co-founded The National Museum of Computing and was a key figure in starting the campaign to save Bletchley Park in the early 1990s.
NOTE 1. Germany entered World War Two with experience in the use of the ENIGMA cypher machine
for military communications. In practice, ENIGMA enciphered messages were transmitted as (ordinary) morse code character sequences
between radio operators, and converted back to plain text with the use of a second machine, upon reception of the message. The machines needed to be set-up exactly the same,
otherwise the received message would be nonsense! The bottom line is that the whole process was labour intensive and quite time-consuming.
Mid-WWII the German High Command adopted the near-instant communication of messages provided by the LORENZ
teletypewriter. These machines encoded the plain text message and transmitted it, automatically in a binary form, as the operator typed. As with ENIGMA, radio was the means
of communication between cipher machines. The plain text of the message would be automatically typed on the receiving
machine, character by character, providing the machines initial settings were identical. For the war-time British code-beakers, it was extremely difficult to decrypt ENIGMA messages,
but they were, relatively, much easier to decrypt than LORENZ messages, which were near impossible without assistance. And of course, in war-time,
the German messages needed to be decrypted in the shortest possible time for the information they contained to be of any military value.
Captain Jerry Roberts, one of the Bletchley Park's shift-leaders in the group known as The Testery, involved in deciphering the LORENZ (FISH) traffic codenamed TUNNY summarised the military value of Bletchley Park's codebreakers' work as:-
ENIGMA decrypts helped Britain not to lose the War in 1941.
TUNNY decrypts helped shorten the European War by at least 2 years.