Editing Automatic Computing Engine (section)

==Background==
The project was managed by [[John R. Womersley]],{{sfn|Copeland|2005|loc=Chapter 3}} superintendent of the Mathematics Division of the [[National Physical Laboratory, UK|National Physical Laboratory]] (NPL). The use of the word ''Engine'' was in homage to [[Charles Babbage]] and his [[Difference Engine]] and [[Analytical Engine]]. Turing's technical design ''Proposed Electronic Calculator'' was the product of his theoretical work in 1936 "[[On Computable Numbers]]"<ref name="Turing1936">{{ Citation | last = Turing | first = Alan M. | publication-date = 1937 | year = 1936 | title = On Computable Numbers, with an Application to the Entscheidungsproblem | periodical = Proceedings of the London Mathematical Society | series = 2 | volume = 42 | issue = 1 | pages = 230–65 | doi = 10.1112/plms/s2-42.1.230| s2cid = 73712 }} (and {{Citation | last = Turing | first = Alan M. | publication-date = 1937 | title = On Computable Numbers, with an Application to the Entscheidungsproblem: A correction | periodical = Proceedings of the London Mathematical Society | series = 2 | volume = 43 | issue = 6 | pages = 544–6 | doi = 10.1112/plms/s2-43.6.544 | year = 1938}})
</ref> and his wartime experience at [[Bletchley Park]] where the [[Colossus computers]] had been successful in breaking German military codes. In his 1936 paper, Turing described his idea as a "universal computing machine", but it is now known as the [[Universal Turing machine]].{{Citation needed|date=October 2015}}

Turing was sought by Womersley to work in the NPL on the ACE project; he accepted and began work on 1 October 1945 and by the end of the year he completed his outline of his 'Proposed electronic calculator', which was the first reasonably complete design of a [[stored-program computer]] and, apart from being on a much larger scale than the final working machine, anticipated the final realisation in most important respects.<ref>"Origins and development of the ACE project", B. J. Copeland, in Copeland (2005).</ref> 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.<ref name=mraths-2016/> The better-known [[EDVAC]] design presented in the ''[[First Draft of a Report on the EDVAC]]'' (dated 30 June 1945), by [[John von Neumann]], who knew of Turing's theoretical work, received much publicity, despite its incomplete nature and questionable lack of attribution of the sources of some of the ideas.
 
Turing's report on the ACE was written in late 1945 and included detailed logical circuit diagrams and a cost estimate of £11,200.{{sfn|Copeland|2005|loc=Chapter 20, Part I, section 10}} He felt that speed and size of [[computer memory|memory]] were crucial and he proposed a high-speed memory of what would today be called 25&nbsp;[[kilobyte]]s, accessed at a speed of 1&nbsp;[[Hertz|MHz]]; he remarked that for the purposes required "the memory needs to be very large indeed by comparison with standards which prevail in most valve and relay work, and [so] it is necessary to look for some more economical form of storage", and that memory "appears to be the main limitation in the design of a calculator, i.e. if the storage problem can be solved all the rest is comparatively straightforward".<ref>''Proposed electronic calculator'', Turing, 1945. Reprinted in Copeland (2005).</ref> The ACE implemented [[subroutine]] calls,{{sfn|Copeland|2005|loc=Chapter 20, Part I, section 6}} whereas the EDVAC did not, and what also set the ACE apart from the EDVAC was the use of ''Abbreviated Computer Instructions,''<ref name=mraths-2016/> an early form of programming language. Initially, it was planned that [[Tommy Flowers]], the engineer at the [[Post Office Research Station]] at [[Dollis Hill]] in north London, who had been responsible for building the Colossus computers, should build the ACE, but because of the secrecy around his wartime achievements and the pressure of post-war work, this was not possible.{{Citation needed|date=October 2015}}