Work began in August 1948, and the first version was operational by April 1949; a program written to search for Mersenne primes ran error-free for nine hours on the night of 16/17 June 1949.
That description provoked a reaction from the head of the University of Manchester's Department of Neurosurgery, the start of a long-running debate as to whether an electronic computer could ever be truly creative.
[1] The computer is especially historically significant because of its pioneering inclusion of index registers, an innovation which made it easier for a program to read sequentially through an array of words in memory.
Thirty-four patents resulted from the machine's development, and many of the ideas behind its design were incorporated in subsequent commercial products such as the IBM 701 and 702 as well as the Ferranti Mark 1.
The chief designers, Frederic C. Williams and Tom Kilburn, concluded from their experiences with the Mark 1 that computers would be used more in scientific roles than in pure mathematics.
[7] Stored-program computers were also being developed by other researchers, notably the National Physical Laboratory's Pilot ACE, Cambridge University's EDSAC, and the US Army's EDVAC.
[9] From about August 1948, the Baby was intensively developed as a prototype for the Manchester Mark 1, initially with the aim of providing the university with a more realistic computing facility.
[10] In October 1948, UK Government Chief Scientist Ben Lockspeiser was given a demonstration of the prototype Mark 1 while on a visit to the University of Manchester.
The machine had 26 initially,[10] increasing to 30 when the function codes to programmatically control the data transfer between the magnetic drum and the cathode-ray tube (CRT) main store were added.
Programs had to be written and submitted in binary form, encoded as eight 5-bit characters for each 40-bit word; programmers were encouraged to memorize the modified ITA2 coding scheme to make their job easier.
The Mark 1 had no system of hardware interrupts; the program continued after a read or write operation had been initiated until another input/output instruction was encountered, at which point the machine waited for the first to complete.
The first realistic program to be run on the Mark 1 was a search for Mersenne primes, in early April 1949,[24] which ran error free for nine hours on the night of 16/17 June 1949.
The algorithm was specified by Max Newman, head of the Mathematics Department at the University of Manchester, and the program was written by Kilburn and Tootill.
During that time 34 patents were taken out based on the team's work, either by the Ministry of Supply or by its successor, the National Research Development Corporation.
The company subsequently licensed several of the patented ideas developed for the machine, including the Williams tube, in the design of its own 701 and 702 computers.
[29] The most significant design legacy of the Manchester Mark 1 was perhaps its incorporation of index registers, the patent for which was taken out in the names of Williams, Kilburn, Tootill, and Newman.
[2] Kilburn and Williams concluded that computers would be used more in scientific roles than pure maths, and decided to develop a new machine that would include a floating point unit.
[30] The successful operation of the Manchester Mark 1 and its predecessor, the Baby, was widely reported in the British press, which used the phrase "electronic brain" to describe the machines.
[31] Lord Louis Mountbatten had earlier introduced that term in a speech delivered to the British Institution of Radio Engineers on 31 October 1946, in which he speculated about how the primitive computers then available might evolve.
[32] The excitement surrounding the reporting in 1949 of what was the first recognisably modern computer provoked a reaction unexpected by its developers; Sir Geoffrey Jefferson, professor of neurosurgery at the University of Manchester, on being asked to deliver the Lister Oration on 9 June 1949 chose "The Mind of Mechanical Man" as his subject.
In response Newman wrote a follow-up article for The Times, in which he claimed that there was a close analogy between the structure of the Mark 1 and the human brain.