Milestones:The Manchester University 'Baby' computer; Small-Scale Experimental Machine (SSEM)


Manchester University "Baby" Computer and its Derivatives, 1948-1951


At this site on 21 June 1948 the “Baby” became the first computer to execute a program stored in addressable read-write electronic memory. “Baby” validated Williams-Kilburn Tube random-access memories, later widely used, and led to the 1949 Manchester Mark I which pioneered index registers. In February 1951, Ferranti Ltd's commercial derivative became the first electronic computer marketed as a standard product delivered to a customer.

Justification for the plaque/citation text.

Three issues are addressed: (a) the inclusion of Williams and Kilburn's names in the citation in relation to the Random Access Memory device; (b) evidence that the Manchester Baby computer was indeed the first of its kind; (c) evidence that the Ferranti Mark I was indeed the first commercially produced computer of this type.

(a). Random Access Memory Device Name.

F C Williams (1911 – 1977) and Tom Kilburn (1921 – 2001) were co-inventors of the Williams-Kilburn Tube. Whilst some texts refer to this device as just the 'Williams Tube', the term 'Williams-Kilburn Tube' is now the universally accepted name of the important random-access memory device upon which the Manchester Baby computer and its derivatives were founded and there is no doubt as to Kilburn's key role in this and later inventions. Williams-Kilburn Tubes were used successfully by sixteen other early computer projects world-wide, before being superseded by ferrite core memories. The invention and development of Williams-Kilburn Tubes is discussed below in the “Memory Development” section.

F C Williams led the computer research team at Manchester University during the period 1947-1950. He headed up the University’s relevant interactions with government (MOS, DSIR and NRDC) and with industry (Ferranti Ltd.) during the exploitation of the Baby’s ideas in the period 1948 – 1951. He continued to lead the Department of Electrical Engineering until his retirement, making notable contributions in the field of variable-speed AC electrical drives.

Tom Kilburn chose the Manchester Baby’s register-level architecture and its instruction set and wrote the first program to successfully run. He took over leadership of the computer design group at Manchester University from 1950 until his retirement in 1981. This group produced four other operational computers, from which three further commercially-available production machines were derived (the Metropolitan-Vickers MV950, the Ferranti Mercury and the Ferranti Atlas). When the UK’s first Department of Computer Science was founded at Manchester University in 1964, Kilburn was appointed Professor and Head of Department. The University subsequently named its Computer Building after him.

Williams and Kilburn both attracted numerous external honours. For Williams, these included Fellow of the Royal Society (1950); the Faraday Medal of the I.E.E. (1972); the Pioneer Award of the IEEE (1972); and the national honours of Officer of the Most Excellent Order of the British Empire (OBE) (1945), Commander of the Most Excellent Order of the British Empire (CBE) (1961) and Knight Bachelor (1976) - [ref. 17b]. For Kilburn, the honours included Fellow of the Royal Society (1965); Fellow and founder member of the Fellowship of Engineering, now the Royal Academy of Engineering (1976); Royal Medal of the Royal Society (1978); Charter Recipient in 1981 of the IEEE Computer Society's Computer Pioneer Award; Eckert-Mauchly Award, ACM & IEEE Computer Society (1983); Fellow of the Computer History Museum (2000); and the national honour of Commander of the Most Excellent Order of the British Empire (CBE) (1973).

(b). The Baby computer as first of its kind.

By ‘first of its kind’ is meant a general-purpose, stored-program, computer which holds both instructions and data in a read/write memory. This formal definition of a modern computer follows the theoretical principles first conceived by Alan Turing in his famous 1937 paper [ref. 15]. As discussed in [ref. 1(b)], , the contemporary mathematician M H A (Max) Newman described the Manchester Baby as “the first of these automatic general-purpose computing machines to have actually worked” [ref. 1(b)]. Newman, who in 1936 was Turing’s tutor at Cambridge, had led the Colossus group at Bletchley Park. After the war Newman had kept in touch with computer design groups in America and the UK. He was writing in October 1948 when he used the phrase ‘automatic general-purpose’ and he certainly knew its meaning.

Various claims to be the first such type of computer have appeared from time to time in the literature, including those for Konrad Zuse’s Z3 (1941), the Atanasov-Berry computer (1942), COLOSSUS (1943), ENIAC (1945), BINAC (March 1949), EDSAC (May 1949). Except for BINAC (1949) and EDSAC (1949), it is believed that the other four machines fail to qualify under the definition of an operational stored-program computer. The various claims are discussed further below in Section 1 and in [ref. 19].

(c). The Ferranti Mark I as first of its kind.

The first of nine Ferranti Mark I and Mark I* (pronounced Mark One Star) computers was delivered to the University of Manchester on 12th February 1951. Confirmation of this date comes from a letter written by Alan Turing in 1951 [ref. 16]. The February Ferranti Mark I was the first commercially-produced stored-program computer to be marketed as a standard product and delivered to a customer. There are other claims in the literature for the first delivery to a customer. These include Konrad Zuse’s Z4 (July 1950), CSAW’s Task 13 (later named Atlas 1, December 1950), UNIVAC (sale announced March 1951, delivery June 1951) and LEO (September 1951 first working but no deliveries to customers). These claims, set in the context of products and markets, are discussed further in Section 1 below and in [ref. 20]. None of these four claims appears to pre-date the delivery of the Ferranti Mark I.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

Bridgeford Street, Manchester M13 9PL; 53.46646363; -2.23482192, Bridgeford Street, Manchester M13 9PL; 53.46646363; -2.23482192

Details of the physical location of the plaque

The University of Manchester’s provisional plan for the precise location is that the IEEE plaque would replace the existing rectangular informational plaque shown in Fig. 1 below

Fig. 1. The exterior wall of the Coupland 1 building in Bridgeford Street, University of Manchester. The IEEE Milestone plaque would be positioned at a suitable point on this exterior north-facing wall. The provisional plan is that the plaque would replace the rectangular grey explanatory panel, seen below the window. Photo courtesy of the University of Manchester.

How the intended plaque site is protected/secured

The public will be able to view the plaque at all hours. Bridgeford Street is pedestrianised and at night this area of the University of Manchester is regularly patrolled by security staff.

Historical significance of the work

On the morning of 21st June 1948 the Small-Scale Experimental Machine (SSEM), more familiarly called the Manchester Baby, was the first electronic stored program digital computer to run a program [ref. 1(a), 1(b)]. Fig. 2 below gives an impression of the moment when a factoring program completed its first successful run of about 52 minutes’ duration, having executed some 3.5 million operations. For an animated impression, see also the 1949 BBC Newsreel clip [ref. 24]. A retrospective video interview with two members of Kilburn’s original team is given here [ref. 25].

Fig. 2. Tom Kilburn (left) and Freddie Williams (right) at the console of the SSEM (Baby) computer. Photo courtesy of the University of Manchester.

In the literature over the years there have been six claims for the first stored-program computer with instructions and data held in addressable read/write memory. Some of these machines were sequence-controlled calculators rather than following the stored-program principle first set out in precise theoretical terms (but not in practical terms) in 1937 by Alan Turing [ref. 15]. Some were demonstrated via small test loops of simple instructions rather than via meaningful programs. Others of the candidates have been special-purpose rather than general purpose. A detailed analysis of the candidates is given in [ref. 19]. In summary, the Manchester Baby computer is considered to have been the first.

A particular criticism of the 1948 Manchester Baby computer has sometimes been that its simple input/output facilities, consisting of a keyboard and screen, were too primitive. Most scholars do not now consider this as a disqualification and in any case 5-track paper tape input/output was added to the enhanced Baby by April 1949. In this respect, the Cambridge EDSAC which ran a program on 6th May 1949 was a much more capable and polished machine with paper tape input/output but it is not considered to have been the first stored-program computer.

It is worth pointing out that the register-level design of the Manchester Baby computer was not unique. It was strongly influenced, as were most early computers, by the work of John von Neumann at the Institute of Advanced Study (IAS) at Princeton, who built on information contained in the June 1945 EDVAC Report. In [ref. 21] there is an analysis of when, and how, such IAS computer design influences probably reached Manchester before 1948. More comments are given in the section on Max Newman below.

Looking at the instruction set that Tom Kilburn devised for the 1948 Baby [ref. 21], the inclusion of both an absolute and a relative control transfer (branch) instruction is an interesting departure from the IAS design. Although the Baby had a limited instruction repertoire, this was by no means the minimal viable set. In the light of hindsight it could have been reduced to just four orders: LDA, STO, SUB and JNE which, together with memory-mapped input/output, would have equipped Baby with an IAS-type architecture and to act as a general-purpose stored-program computer.

Looking back, one could say that the 21st June 1948 marked the start of software development and the birth of the Computer Age. When the Manchester Baby first worked, however, it was noticed by contemporary computing pioneers more for its memory system than for its first program – which was small, only 25 instructions [ref. 1(c)]. The Baby’s memory system was important because at that time “The most difficult problem in the construction of large-scale digital computers continues to be the question of how to build a memory” [ref. 2].

Memory Development

In the post-war years several potential memory technologies were being suggested, such as: thermionic valves, electro-mechanical relays, magnetic drums, tape or wire; mercury or magneto-strictive delay lines; electrostatic charge-storage devices. The important design parameters for a computer’s primary memory included: capacity, access-time, cost per bit, reliability.

One of the groups investigating charge storage devices was at MIT, where Cathode Ray Tubes (CRTs) were being assessed for permanent echo-cancellation in radar equipment. Williams, who at that time worked at the prestigious Telecommunications Research Establishment (TRE) at Great Malvern, visited MIT in November 1945 and June 1946 [ref. 17(a)]. He saw the MIT experiments. He realised that CRTs could not be used unmodified for computer storage because the charge leaked away in about 0.2 seconds. Some means of automatic refresh was needed. Back at TRE in the summer of 1946 Williams invented a method for automatic refreshing using the Anticipation Pulse effect, which was arrived at after careful observation of shape/distribution of the stored charge and the resulting shape/timing of the voltage signal induced on the CRT’s pick-up plate. The first of many patents for what were called Williams Tubes was filed on 11th December 1946 with the title Apparatus for storing trains of pulses [ref. 3(a), 3(b), 3(c)]. At some time after F C Williams died in 1976, historians began to refer to the invention as Williams-Kilburn Tubes and that is the name used in this document and the citation. It acknowledges that Tom Kilburn did most of the post-1946 research that turned the original invention into a robust memory system.

At Manchester University from January 1947 onwards, F C Williams and Tom Kilburn successively improved their memory-related inventions [ref. 3(a), 3(b), 3(c)]. They investigated how a scanning beam could detect in advance the condition (1 or 0) of a stored digit and hence be able to refresh this digit’s value. Refreshing scans could be overlapped with normal randomly distributed program access to memory. Selection-time was independent of physical location. So the whole Williams-Kilburn Tube (see Fig. 3 below) was a random-access device, similar in concept to today’s RAM. It was suitable for both serial and parallel computer architectures.

Fig. 3. The components of one Williams-Kilburn random-access memory. Photo courtesy of the University of Manchester.

By January 1948 experiments to refine the refreshing techniques had been conducted. Binary representations based on focus/defocus and dot/dash had been explored. The time had come to build a Small Scale Experimental Machine (SSEM), familiarly called the Manchester Baby computer, to verify that the Williams-Kilburn memory could perform satisfactorily when subject to the sustained activity of high-speed computing during meaningful program execution.

In America in the late 1940s there were other attempts to build random-access memory systems. Pioneering computing teams such as that of John von Neumann at Princeton were hoping to use a random-access memory device called the Selectron [ref. 4(a), 4(b), 4(c)]. The Selectron was under development from 1946 by RCA. However, as the Selectron was never fully available commercially, Princeton adopted Williams-Kilburn Tubes instead. IBM followed suit, licensing Williams-Kilburn Tubes for their 700-series computers before the advent of ferrite core stores – (see Fig 4 below). The Whirlwind project at MIT developed a special holding beam storage tube, which was random-access but considerably more complex than Williams-Kilburn tubes. Whirlwind first did useful work in March 1951. The Princeton computer first did useful work in the summer of 1951.

By 1953 the Baby’s Williams-Kilburn random access memory technology was sufficiently important to have been adopted by 17 other pioneering computer design groups world-wide [ref. 18]. To put this in context, by 1953 there were about 60 stored-program computers in operation world-wide, though most of them were prototypes and not for sale. About 48% of these computers were employing serial magnetic drum storage for their primary memories, 24% used Williams-Kilburn Tubes and 21% were using serial delay lines. [ref. 18]. The first computer to become operational using mercury delay line storage is believed to have been the Cambridge University EDSAC, in May 1949.

Fig. 4. Williams-Kilburn electrostatic storage units as used under licence by IBM for their IBM 701 and 702 computers. Looking on are (Left-to-right): F C Williams, H J Crawley (NRDC) and J C McPherson (IBM). Photo courtesy of the University of Manchester.

Index, or modifier, registers

The cost per bit of Williams-Kilburn Tubes made them an economically attractive technology for central registers as well as for primary memory. One Williams-Kilburn Tube could easily store eight 32-bit central registers, at about one fiftieth the cost-per-bit of flip-flop registers. By April 1949 this fact led the Baby’s team to add a set of general-purpose index (or modifier) registers to their computer – a significant architectural innovation still in use today [ref. 5(a), 5(b)]. The registers, called B lines in 1949, were held in the B storage tube with facilities to load/store values into the B lines, subtract unity from a B line and branch conditionally on the value of a selected B line. The symbol B was used simply because the letters A and C already appeared in the Manchester computer’s register-level description. See [ref. 13] for relevant diagrams. An initial problem solved by index registers was how to carry out calculations on arrays and vectors without the need for self-modifying code.

The Manchester patent for index registers was filed on 3rd June 1949, in the names of F C Williams, T Kilburn, G C Tootill, A A Robinson and M H A Newman. Over the next 20 years the topic of address-generation for structured data was to exercise Tom Kilburn’s computer design team, as they developed a distinctive Manchester style of computer architecture. This led to the array of 128 fast modifier registers (the B store and the B-arithmetic unit) for the Atlas computer in 1962 [ref. 22] and the ‘zero, one or infinity’ principle of address-generation registers and an associatively-accessed Name Store in the Manchester MU5 computer (1972) [ref. 24a, 24b].

The role of Max Newman in the Manchester computer developments

Professor M H A (Max) Newman’s name on the index register patent represents possibly the only documented technical contribution made by Newman himself to the early Manchester computer ideas. And yet Max Newman, as Professor of Mathematics, had been the inspiration for Manchester’s involvement with stored-program computers ever since his arrival in the autumn of 1945. Although perhaps better known today for his leadership of the Colossus team at Bletchley Park during the war, Max Newman became convinced that post-war effort at Manchester should be directed at starting a ‘calculating machine laboratory’, for which he successfully applied to the Royal Society for a grant in 1946 [ref. 28].

In hindsight, Newman’s initial objective does not seem to have been directed at producing a single general-purpose, stored-program, computer but rather to investigate a series of pilot models of electronic machines to deal with mathematical problems [ref.28]. By the summer of 1946, evidently Newman had changed direction. He had recruited two Bletchley Park mathematicians (David Rees and Jack Good) to Manchester and had set about learning first of the computer design work being done elsewhere on general-purpose computers. He visited Alan Turing in the summer of 1946 at the National Physical Laboratory and then visited John von Neumann’s IAS team at Princeton in the autumn of 1946. Newman and Good decided to adopt the accumulator-based IAS register-level architecture for a Manchester computer – as indeed did most other early computer projects. Newman hoped to use Selectron storage tubes [refs. 1(b) and 12] at Manchester, but this never happened.

Meanwhile, Newman actively sought the appointment of a skilled electronics engineer to Manchester, to get the computer project off the ground. As described above, such an engineer, F C Williams, was recruited to the Chair of Electro-Technics at Manchester in December 1946.

Max Newman’s efforts at establishing a computing group at Manchester are documented in [refs. 25a, 25b, 25c, 25d], which should be read in conjunction with the more recent [ref. 21]. In his efforts, Newman was supported by two other distinguished Manchester academics: Douglas Hartree, who was Professor of Applied Mathematics from 1929 to 1946 and Patrick Blackett, Professor of Physics from 1937 to 1953. Blackett and especially Hartree were key to the early transfer of ideas between the ENIAC/EDVAC/IAS developments in America and the embryo computer design groups in the UK and in Australia in the period 1946 to 1950. Significantly Hartree, who was actively involved in computing during the war, was the only non-American lecturer at the Moore School in the summer of 1946 [ref. 26] and so well-placed to act as a channel of communication.

Jack Good, rather than Max Newman, seems to have been the Manchester mathematician most interested in the practical details of stored-program computers [ref. 21]. Unfortunately Jack Good left Manchester in April 1948 to return to GCHQ but the outstanding mathematician Alan Turing joined Newman’ Mathematics Department in October 1948. Turing’s salary was the first call upon the Royal Society grant. Thus, Newman and Turing were in place in 1949 to advise Williams and Kilburn on system software for the Manchester Mark I computer. See Fig. 8 below for a view of this machine in June 1949. Newman and Turing also specified an intrinsically useful program (investigation of Mersenne Primes) which ran in April 1949. Finally, Newman agreed to spend £20,000 of his Royal Society grant on the provision of a new, custom-designed, Computing Machine Laboratory which was required to house the Ferranti Mark I computer when it was delivered in February 1951.

Pausing Newman and Turing’s account for a moment, we should now go back and pick up the activities of Williams and Kilburn in 1948, once they had proved that their random-access memory system had worked satisfactorily.

Further enhancements

From July 1948 the University team made the following improvements to the Manchester Baby: increasing the primary memory; extending the word-length from 32 to 40 bits and adding a double-length accumulator; increasing the instruction repertoire to 26 orders including fast hardware multiply; adding modifier registers (see above); adding a magnetic drum secondary memory with a unique coding system (Phase Encoding, still in use today) [ref. 13]. The drum secondary memory became operational in April 1949 via manual intervention. Full program control of the drum was implemented in October 1949. The 1949 enhanced Baby machine was known as the Manchester Mark I, or sometimes MADM.

Fig. 5. A storage tube’s contents, when displayed for programmers’ convenience on the console monitor as two pages, each of 32 5-bit characters per line. The extra 65th line at the top left is the associated drum address of these pages on the drum backing store. Photo courtesy of the University of Manchester.

The Manchester Mark I computer was probably the first machine to contain the now-familiar combination of two physical levels of on-line storage: a faster but smaller primary section plus a slower but larger secondary memory. At Manchester the unit of transfer between the two levels was the page – an obvious term when one looks at information displayed on the screen of a Williams-Kilburn Tube. See Fig. 5 above. At the top left of the photo can be seen an extra 20-bit line, which contains the track address of these two pages of information when stored on the drum. The 65th line was a programmer-accessible page address register. By about 1959 this feature was to lead to the idea of hardware-assisted page-address translation and the management of Virtual Memory in the Manchester/Ferranti Atlas computer [ref. 22].

As for the term ‘virtual’, it might be significant that R A (Tony) Brooker, writing in 1955, described the Mark I’s secondary memory as ‘virtually infinite’ when compared with the primary memory [ref. 8(a)]. It was certainly larger than that of any other computer available in the UK until 1956 when the Elliott 405 was introduced [ref. 7]. Furthermore and unusually, in the Manchester Mark I and Ferranti Mark I the drum was synchronised to the CPU – technically difficult but allowing multiple drums to be connected as secondary memory. The Ferranti Mercury had multiple drums, as did Atlas.


The strategic importance of the Baby and its memory system were quickly recognised. At the suggestion of Professor Patrick Blackett, in October 1948 Sir Ben Lockspeiser, Chief Scientist at the Ministry of Supply (MOS), paid the Baby a visit. On 26th October Lockspeiser initiated a UK government contract with the long-established electrical company Ferranti Ltd. to produce a fully-engineered production version of the Manchester Baby [ref. 6]. The resulting production computer was at first confusingly known locally as the Manchester Electronic Computer Mark II or casually and even more confusingly as the Production Mark I but this was soon changed to the Ferranti Mark I. See Fig. 6 below.

Fig. 6. The Ferranti Mark I computer, as installed at the University of Manchester in February 1951. Photo courtesy of University of Manchester.

In total, the company produced two Ferranti Mark I computers and seven upgraded versions, the Mark I* (pronounced Mark One Star). A detailed description of all nine installations is given in the book referenced as [Ref 7]. See also Fig. 7 below which shows a Mark I* installation. A Ferranti Mark I was installed at the University of Manchester on Monday 12th February 1951 (see Fig 6. above) – a world first for the delivery of a commercially-available computer marketed as a standard product. Constructional details of the Ferranti Mark I are described in [ref. 14(a)]; its software is described in [ref. 8(b)]. The background to the academic/industrial co-operations which led to the Ferranti Mark I are given in [ref. 14(b)].

By the mid-1950s American companies such as Univac and IBM were installing tens of general-purpose computers in the USA. For various reasons both economic and strategic, it was not until about 1956 that American-produced computers reached non-American destinations. It seems that, in the period 1951 to 1955, Ferranti Ltd. was the only manufacturer willing and able to deliver more widely [ref. 7]. Thus, the first substantial computers to be delivered and put to use in Canada, Holland, Italy and the UK were Ferranti Mark I or Mark I* machines. The first non-British computer to reach the UK was an IBM 650, delivered in October 1956 [ref. 7].

Whilst the hardware and architecture of early Manchester and Ferranti computer designs was innovative and patented [ref. 3(a)], the software was initially far from user-friendly. Indeed, to modern eyes, coding appears fiendishly difficult [ref. 8b]. Steps were eventually taken to improve this [ref. 8(a)]. First into action was A E (Alick) Glennie, a programmer from the Armaments Research Establishment (ARE) and later from the Atomic Weapons Research Establishment (AWRE), who used the Ferranti Mark I at Manchester until Mark I* computers were delivered to the ARE and AWRE MOS sites. In 1952 Glennie began to experiment with a language which he called Autocode. This was an automatic coding system which, though only used by Glennie himself, is regarded as the first tentative steps towards high-level languages [ref. 8(b)].

Fig. 7. An example of a Ferranti Mark I* computer, as installed in July 1954 at the Armament Research & Development Establishment, Fort Halstead, Kent. Photo:Crown Copyright.

By 1954 Tony Brooker had significantly amplified Glennie’s ideas and introduced his own Mark I Autocode to users [refs. 8(a) and 8(c)]. Based on a detailed analysis of the work of Glennie and Brooker, it has been said that by 1954 “the Mark I became possibly the easiest machine to program in Britain” [ref. 8(b)]. Example Autocode programs are given in [ref. 8(a), 8(b) and 8(c)]. Brooker’s Mark I Autocode, arguably the first high-level language to gain popular appeal, was released to users in March 1954. This was a year or so ahead of Fortran developments.

At a more basic level, Ferranti’s modifications in moving from Mark I to Mark I* mainly consisted of rationalising the instruction set from 50 to 32 orders (hence requiring one 5-bit teleprinter character per instruction). This was done in the light of experience of using the computer for real-world scientific and engineering applications. Such applications dominated the market in the early 1950s. Some of the instructions omitted in the Mark I* were originally specified by Max Newman and Alan Turing, most probably based on their own research interests. Examples are the population count (sideways add) and the hardware random number generator. A full list of changes from Mark I to Mark I* is described in [ref. 23].

Features that set this work apart from similar achievements

Manchester University’s early computer design efforts were characterised by the production of useful results by a small academic team, leading to fruitful co-operation with local industry. From January 1947 to September 1948 the hardware team essentially consisted of just three people: F C Williams, Tom Kilburn and Geoff Tootill. In support they had two lab technicians, so-called ‘wiremen’, though one of them was female (Ida Fitzgerald). In September 1948 the research team was joined by three hardware research students.

The hardware designs were passed to Ferranti Ltd. in the period between December 1948 and November 1949, with appropriate exchange of personnel between academia and industry. About 35 computer-related patents were filed by F C Williams and colleagues at Manchester University between November 1947 and March 1950 [ref. 3(a)]. This was almost three times the total number of patents filed by all the other UK computer design groups over the same period.

On the software side, Alan Turing came to Manchester University in October 1948 from NPL. Alan Turing was responsible for the input/output routines and other basic library subroutines of Manchester Mark I and Ferranti Mark I computers. An assistant mathematician, Cicely Popplewell, was appointed in October 1949. Then in October 1951 R A (Tony) Brooker arrived to head up the University’s Computing Service. In summary, the academic software team associated with the early Manchester computers was also relatively small.

In the case of the Ferranti Mark I, Ferranti soon built up a team of programmers at its nearby Moston factory where the production machine had been built. By April 1953 the Moston programmers numbered about fourteen degree-level mathematicians, over half of whom were female. The University and Ferranti software teams naturally collaborated, though after about 1953 when the Ferranti Mark I* came onto the market, Moston’s focus shifted to the Mark I* with its rationalised instruction set.

Early end user activity

Alan Turing and Max Newman were the first end-users of the Manchester Mark I computer. Useful theoretical work was done in the spring of 1949 and in the period October 1949 to August 1950, investigating Mersenne primes and the Riemann hypothesis. A more practical application initiated by Gordon Black, a Physics research student, involved optical ray tracing for high-precision lens design. There was then a pause whilst a new building, the Computing Machine Laboratory, was completed to house the production computer. The Ferranti Mark I arrived in February 1951. Alan Turing issued the 100-page Users’ Programming Manual in March 1951 and many copies were distributed.

From its very small beginnings in 1948, use of the computing facilities at Manchester University grew rapidly after the installation of the Ferranti Mark I. During calendar year 1955, 104 people were trained to use the machine and 66 scientific papers were published based on machine results [ref. 1(c)]. The community of users at Manchester had grown to include 15 University departments, three industrial research associations, seven engineering companies and nine government establishments [ref. 1(c)]. By 1955 a total of seven Ferranti-manufactured derivatives of the Manchester Baby had been installed at customer’s sites and a further two computers would be installed by the end of 1957. The nine sites together covered four countries: UK, Canada, Holland and Italy [ref. 21]. The influence of the 1948 Small-Scale Experimental Machine (the Baby) therefore grew, making its presence on the world stage.

Significant references


1. (a). F C Williams & T Kilburn, Electronic digital computers. Letter to Nature, vol. 162, September 1948, page 487. This Letter includes a brief description of the Manchester Baby computer and is the first publicly-available announcement of its successful operation. See also Fig. 2 above.

1 (b). M H A Newman, Status Report on the Royal Society Computing Machine Laboratory, prepared for an internal committee of the Senate of the University of Manchester, 15th October 1948. Max Newman, Professor and Head of Mathematics at Manchester University, had obtained a grant from the Royal Society in 1946 to establish a Computing Machine Laboratory [ref. 28]. In his October 1948 Report Newman explains the difficulties in acquiring a digital computing machine for his proposed Laboratory. He highlights the engineering problems in finding “a satisfactory memory unit or method of storage of information” and the delays in obtaining Selectron memory units from RCA. Newman goes on to state that “a small prototype of the [digital computing] machine using Professor Williams’ storage came into action about three months ago in the Electrical Engineering Laboratory and is thus the first of these automatic general-purpose computing machines to have actually worked”. Significantly, Max Newman had led the Colossus cryptanalytical group at Bletchley Park during the war. In the summer of 1946 Newman visited Alan Turing at the National Physical Laboratory to learn about the ACE project. From October to December 1946 Newman visited John von Neumann’s computer design group at the Institute of Advanced Study at Princeton. Newman had organised a Discussion on Computing Machines at the Royal Society, London, on 4th March 1948 at which there were short presentations from most of the UK’s embryo computer design projects. Max Newman would therefore have been aware of any stored-program machine that might have pre-dated the Manchester Baby. It is believed that the main challenger was the EDSAC computer at the University of Cambridge, which first ran a program on 6th May 1949.

1 (c). The first program is reproduced in: S H Lavington, A History of Manchester Computers, Second edition, published in 1998 by the British Computer Society. ISBN 0-902505-01-8. The Baby’s first program consisted of a factoring algorithm with data designed at first to give shortish runs to make any necessary circuit adjustments. This made good practical sense during the Baby’s commissioning phase. Thus this factoring program could be given a more and more ambitious target number to factorise, yielding longer and longer run times. The code (ie the list of instructions) remained the same. A more detailed description of the code and the probable sequence of adjusting data to give longer run times is given in [ref. 1(d)].

1(d). G C Tootill, The original original program. Resurrection, the Journal of the Computer Conservation Society, number 20, summer 1998. See:

2. Nathaniel Rochester (IBM), Radio progress during 1949: electronic computers. Keynote paper in the Proceedings of the IRE, April 1950, pages 373 - 375.

3 (a). The Williams Tube (or more fairly the Williams-Kilburn Tube) stored digital information as a matrix of electrostatically-charged areas on the phosphor coating of a cathode ray tube. See Fig. 3 above. The unique feature of the Williams-Kilburn Tube was its method of automatically refreshing the charge pattern before it decayed. The economic benefit of the system was its low cost per bit: it could be built from standard CRTs. The first patent for Williams Tube memory was UK Application Number GB19460036587, with the title of Apparatus for storing trains of pulses. This was filed on 11th December 1946 in the name of F C Williams who was at the time employed by the government’s Telecommunications Research Establishment. A number of subsequent storage patents followed, mostly in the joint names of F C Williams and T Kilburn. The list of all patents emanating from F C Williams’ Manchester University computer design team in the period January 1947 to 1st March 1950 is given below, based on an analysis of all patents from January 1943 to October 1991 inherited by or administered by NRDC. (This analysis was compiled in 2018 by Roger Cullis, a former NRDC senior patent attorney, using data from the European Patent Office World Patents Index).

The time-period of the following Manchester University patents embraces all the novel technical developments associated with the SSEM and its subsequent enhancements:

Date Title of patent Name(s) of inventors
20/10/47 Electrical information storage apparatus FCW, TK
22/05/48 Information storage means FCW, TK
26/07/48 Improvements in or relating to electronic ccts for digital comp. systems FCW, TK
26/07/48 Electronic circuit for adding binary numbers FCW, TK
13/10/48 Electronic digital computing apparatus FCW, TK
01/11/48 Electrical information storage apparatus FCW, TK
23/12/48 Pulse selecting circuits FCW, AAR, TK
23/12/48 Circuit for adding binary numbers FCW, AAR, TK
23/12/48 Circuit for multiplying binary numbers AAR
23/12/48 Pulse selecting circuits FCW, AAR, TK
31/01/49 Electronic digital computing device FCW, TK
1/03/49 Magnetic storage systems for electronic binary digital computers FCW, JCW
1/03/49 Magnetic storage systems FCW
14/03/49 Improvements in or relating to electronic ccts for multiplying binary nos FCW, AAR
14/03/49 Electronic circuit for multiplying binary numbers FCW, AAR
3/06/49 Electronic digital computing devices [This patent refers to B-lines, later known as Index registers] FCW, TK, GCT, AAR, MHAN
7/06/49 Electrical information storage means FCW, TK, GCT
7/06/49 Improvements in or relating to electronic digital computors FCW, TK, GCT
7/06/49 Electronic digital computers FCW, TK
22/06/49 Electronic digital computing machines FCW, AAR
22/06/49 Electronic digital computing machines FCW, TK, GCT, GET, DBGE
22/06/49 Electronic computing devices with subsidiary storage FCW, TK, GET, DBGE, GCT
22/06/49 Improvements in or relating to digital computors FCW, TK, GET, DBGE, GCT
22/06/49 Improvements in or relating to electronic digital computing machines FCW, TK, GET, DBGE, GCT
22/06/49 Electronic digital computing machines AAR, FCW, TK
8/08/49 Electrical signal detecting and amplifying systems FCW, TK
17/08/49 Electronic digital computing machines FCW, TK
17/08/49 Electronic digital computing machines FCW, TK, GCT
14/11/49 Electronic storage devices FCW, TK
14/11/49 Electronic information storage devices FCW, TK, GCT
16/11/49 Digital computing machine FCW, TK, GET
16/11/49 Improv in magnetic rec or reproducing devices partic for dig comp mcs FCW, TK, GET
22/11/49 Electronic information-storing devices FCW, TK
1/12/49 Electrical storage apparatus FCW, TK, GCT
19/01/50 Electronic information storage device FCW
16/02/50 Improvements in or relating to electronic information-storing devices FCW
1/03/50 Magnetic storage system for electronic binary digital computers FCW, JCW

The identification and biographical notes for the inventors in the above table are as follows:

Initials Name Relevant dates at Manchester University,
status during period ending March 1950, etc.
DBGE Dai Edwards Sept. ’48 onwards; EE research student
TK Tom Kilburn Dec. ’46 onwards; TRE employee, then EE lecturer
MHAN Max Newman Oct. ’45 onwards; Professor of Maths
AAR Alec Robinson April ’47 – April ’49; EE research student, then to Ferranti
GET Tommy Thomas Sept. ’48 – Sept. ’55; EE research student
GCT Geoff Tootill Sept. ’47 – Nov. '49; TRE employee, then to Ferranti
JCW Cliff West Oct. ’46 – Dec. ’57; EE research student, then assistant lecturer
FCW FC (or Freddie) Williams Dec. ’46 onwards; Professor of EE

The first widely-circulated report describing the Williams-Kilburn storage technology was:
3 (b). T Kilburn, A storage system for use with binary digital computing machines. The report was dated 1st December 1947 and was typed on foolscap format paper. It consisted of 52 pages of text, 32 pages of diagrams and one page with three photos. This report was produced for the Telecommunications Research Establishment (TRE). At the time Kilburn was on secondment from TRE, working with Professor F C Williams in the Electro-technics Department at Manchester University. It is known that several copies of this Report were taken to the USA in the spring of 1948 by Douglas Hartree (Cambridge University), Harold Huskey (SWAC at UCLA) and A M Uttley (TRE).

The first paper to appear in a scientific journal was:
3 (c). F C Williams & T Kilburn, A storage system for use with binary digital computing machines. Proc. IEE, Vol. 96, part 2, No. 30, 1949, pages 183 ff.

4 (a). Jan Rajchman, The Selectron. Symposium of large scale calculating machinery, Harvard University, January 8th 1947. See Mathematical Tables and Other Aids to Computation (MTAC) vol. 2 page 22 – 25. The final state of Selectron development is described at length here:

4 (b). The Selective Electrostatic Storage Tube. RCA Review, Volume 12, No. 1, pp 53 - 97, March 1951.

4(c). A smaller 256-bit version of the Selectron was used on the RAND Corporation JOHNNIAC in 1953 before being replaced by magnetic core memory. See:

5 (a). The idea of index registers, initially called B lines on the Manchester University computer, arose sometime between 15th July and 13th October 1948. Evidence comes from G C Tootill’s laboratory notebook, which is preserved as item NAHC/MUC/2/C3 in the National Archive for the History of Computing in Manchester. (See, for example, under Extra facilities on the 13th October notebook entry). Working B line hardware was in use on the computer by April 1949. The relevant UK Patent was filed on 3rd June 1949 – see list in ref. 3(a) above.

5 (b). The first paper to appear in a scientific journal that mentions the modifier registers is: T Kilburn, The University of Manchester universal high speed digital computing machine. Nature, Vol. 164, Oct. 1949, pages 684 – 691.

6. The full text of the 26th October 1948 letter sent by Sir Ben Lockspeiser to Eric Grundy, Manager of Ferranti’s Instrument Department at Moston, Manchester, reads as follows:

Dear Mr Grundy,

I saw Mr Barton [MOS] yesterday morning and told him of the arrangements I made with you at Manchester University. I have instructed him to get in touch with your firm and draft and issue a suitable contract to cover these arrangements. You may take this letter as authority to proceed on the lines we discussed, namely, to construct an electronic calculating machine to the instructions of Professor F C Williams. I am glad we were able to meet with Professor Williams as I believe that the making of electronic calculating machines will become a matter of great value and importance.

Please let me know if you meet with any difficulties”.

7. S H Lavington, Early computing in Britain: Ferranti Ltd. and government funding, 1948 – 1958. Published by Springer, 2019. ISBN: 978-3-030-15102-7. See especially Chapter 5.

8 (a). R A Brooker, An attempt to simplify coding for the Manchester computer. British Journal of Applied Physics, Vol. 6, September 1955, pages 307 – 311. R A (Tony) Brooker, who took over from Alan Turing in October 1951 as leader of the systems software support for the Ferranti Mark I, developed a high-level language (an Autocode) for the computer. The Autocode was released to users in March 1954.

8 (b). M Campbell-Kelly, Programming the Mark I: early programming activity at the University of Manchester. Annals of the History of Computing, Vol. 2 no. 2 April 1980, pages 130 – 168. This comprehensive paper includes a detailed explanation of the Ferranti Mark I’s software.

8 (c). Brooker’s Mark I Autocode avoided three difficulties facing all early programmers:

(i) the awkward machine code in which programs had to be written, making software difficult to update and adapt;

(ii) the necessity for the user to frequently swap information between the fast (but small) primary memory and the slow (but large) secondary memory during run time;

(iii) scaling and precision: the need to be aware of the limited number-range of fixed-point and to perform most scientific and engineering calculations in floating-point arithmetic, for which there was no hardware support.

The Mark I Autocode is best introduced by a short sequence which prints the root mean square (RMS) of the floating-point variables v1, v2, … v100: The formatting of this code is as it was originally written.

        n1 = 1
        v101 = 0
      2v102 = vn1 x vn1
        v101 = v101 + v102
        n1 = n1 + 1
        j2, 100 ≥ n1
        v101 = v101/100.0
      *v101 = F1(v101)

The 5-track paper tape for this sequence would have been prepared on a special teleprinter in the Computing Machine Laboratory which had been adapted with appropriate printable symbols (illustrated here in the type font Times New Roman). In the Autocode convention, n1 is an integer and v1 etc are floating-point numbers. The symbol * causes the printing of a variable to ten decimal places on a new line and F1 signifies the intrinsic function square root. The format (spacing, etc.) in the above example conforms to the original Autocode rules.

The Autocode was released to users a year or two ahead of Fortran developments. As Campbell-Kelly says [ref. 8(b)], “Brooker’s Mark 1 Autocode was probably the most significant programming innovation of the mid-1950s in Britain; it inspired several imitations at the time when American directions were not widely reported in Britain”. Autocodes were developed for a range of British computers by Ferranti Ltd., Elliott Automation Ltd. and ICT. By 1961 the world-wide proliferation of high-level languages had led the Manchester team to develop the Compiler Compiler [ref. 9 (a, b, c)], another software landmark.

9 (a). The basis for the Compiler Compiler was first described in: R A Brooker & D Morris, An assembly program for a phrase structure language. Computer Journal, Vol. 3(1960), page 168.

9 (b). A number of UK-based papers followed but the developments did not come to universal attention until this publication: S Rosen, A Compiler-Building System Developed by Brooker and Morris. Comm. A.C.M., Vol. 7, No. 7, July 1964, pages 403 - 414.

9 (c). The history of the Compiler Compiler development, including a retrospective Appendix by Tony Brooker, is presented here: S H Lavington and others: Tony Brooker and the Atlas Compiler Compiler. February 2014 & revised April 2016:

10. The outgoing Professor Willis Jackson and his research group quit the Department of Electro-Technics in September 1946. This left the Electro-Technics Department severely depleted and especially so in the area of electronics. Albert Cooper, the Department’s Chief Technician, was reported to be “disgusted” with Jackson’s move because it seemed to him that “the whole of the Department was disappearing into Jackson’s van”. The full history is recounted in: Electrical Engineering at Manchester University; the story of 125 years of achievement. T E Broadbent. Published by The Manchester School of Engineering, University of Manchester, 1998. ISBN 0 – 9531203 – 0 – 9.

11. On 19th and 22nd August 1949 F C Williams gave two lectures in Canada at the National Research Council’s Atomic Energy project, Research Division, Chalk River, Ontario. These lectures were typed up from a wire recording and bound as Report LT-24, 14th Sept. 1949, High speed universal digital computers. (28 typed pages and 16 figures). This Report essentially describes the Williams-Kilburn CRT storage system, the SSEM computer and the June 1948 factoring program. Report LT-24 is preserved as item NAHC/MUC/1/D5 at the National Archive for the History of Computing in Manchester.

12. It is clear from Jack Good’s notes that Max Newman intended to build or acquire a computer with a Selectron (or equivalent) memory, following the advice of the computer group at Princeton. Surviving records are sparse but Jack Good kept notes from which it seems that the Manchester mathematicians favoured a machine based on von Neumann’s IAS project at Princeton rather than on Alan Turing’s ACE project at NPL. Good’s notes are available as follows: Early Notes on Electronic Computers. I J Good. 78 typed and hand-written pages mostly covering the period 1947-8, with Good’s retrospective introduction dated 23rd March 1972, and Good’s covering letter to Simon Lavington dated 7th April 1976. Catalogue NAHC/MUC/2/A4 in the National Archive for the History of Computing. An analysis of Good’s notes is given in reference 7 above. An example of a specific mention of the Selectron is given in Good’s notes for 16th February 1947.

13. F C Williams & T Kilburn, The University of Manchester computing machine. Inaugural conference of the Manchester University computer, July 1951, pages 5 – 11. This paper was also presented at the Joint AIEE/IRE Computer Conference, Philadelphia, December 1951. This illustrated paper describes the progression from the 1948 Small Scale Experimental Machine (Baby) computer, via 1949 enhancements, to the final commercial version known as the Ferranti Mark I.

14 (a). B W Pollard & K Lonsdale, The construction and operation of the Manchester University computer. Proc IEE, Vol. 100, part 2, 1953, pages 501 – 512. See also Fig. 6 above.

14 (b). T Kilburn, G C Tootill, D B G Edwards & B W Pollard, Digital computers at Manchester University. Proc. IEE, Vol. 100, part 2, 1953, pages 487 – 500.

15. A M Turing, On computable numbers, with an application to the Entscheidungsproblem. Proceedings of the London Mathematical Society, Series 2, Vol. 42, issue 1, January 1937, pages 230–265. Although theoretical computer scientists honour this paper as setting out the fundamentals of general-purpose computation, the paper had little if any influence on the groups who actually designed and built the first general-purpose computers in the 1940s and 1950s. It is incorrect to assert, as some still do, that Alan Turing ‘invented the computer’. See also reference 26 below.

16. Andrew Hodges, Alan Turing: the Enigma. Published by Burnett Books in 1983. This 600-page biography is a classic. The letter from Alan Turing to Mike Woodger at NPL was written during the week prior to the Ferranti Mark I’s arrival on 12th February 1951. Extracts are quoted by Hodges on page 437.

17 (a). T Kilburn and L S Piggott, Frederic Calland Williams. Biographical Memoirs of Fellows of the Royal Society: Published in 1978. See Volumes 1-26 (1955-1980), pages 582 – 604.

17 (b). For an explanation of national honours in the United Kingdom see:,_decorations,_and_medals_of_the_United_Kingdom

18. Technical information on other computers to have used Williams-Kilburn Tubes by 1953 is available here: A survey of automatic digital computers. Office of Naval Research, Department of the Navy, Washington DC. Report 111293. 1953. See: In summary, 97 computers are included in this 1953 Survey, of which 34 were not stored-program machines. Of the 63 stored-program computers, 30 (48%) used a magnetic drum for primary storage, 13 (21%) used delay lines, one used Selectrons, one used holding-beam CRTs and 15 (24%) used Williams Tubes. To those Williams Tube machines in the 1953 Survey should be added two more, bringing the total to 17. Thus the final list of computers using Williams-Kilburn Tubes in about 1953 or soon after is likely to have been: AVIDAC (1953), BESK (Sweden, 1954), ERA 1103 (1954), IBM 701 (1953), ILLIAC (1952), IAS (1952), Ferranti Mark I (1951), Ferranti FERUT (Toronto, 1952), NAREC (1954), ORACLE (1953), STRELA-1 (Moscow, 1953), SWAC (1952), TAC (Tokyo, 1954), TC-1 (1955), TREAC (1953), UTEC (Toronto,1952). In addition, three special-purpose digital computers used Williams-Kilburn Tubes: the Elliott 152 for real-time moving target radar control, the Elliott 153 for D/F calculations and the GCHQ OEDIPUS rapid analytical machine for cryptanalysis. These are described in: Moving Targets: Elliott-Automation and the dawn of the computer age in Britain, 1947 – 67. Simon Lavington. Published by Springer in 2011.

19. Claims for the first general-purpose, stored-program, computer to hold both instructions and data in a read/write memory have appeared from time to time in the literature. Besides the Manchester SSEM ( Baby), here are six other frequently-quoted candidates:
Konrad Zuse’s Z3 (Berlin,1941) was built for engineering calculations, for which it was successfully employed. It was not a stored-program computer, since it held instructions externally on perforated 35mm film stock. Z3 was hardly general-purpose in the normal sense of the phrase.
Atanasov-Berry Computer,ABC (Iowa State College,1942), designed for the solution of systems of simultaneous linear equations, on which the machine was tested before the project was abandoned because of the exigencies of war.
COLOSSUS (the UK’s Government Code and Cipher School, 1943), a rapid analytical machine designed to aid decryption of the Lorenz ciphers and similar.
ENIAC (University of Pennsylvania, 1945), designed primarily for producing ballistic firing tables. It was moved to the Aberdeen Proving Ground, modified in 1948 and later used for calculations related to nuclear weapons. Programs were initially set up manually, via a plugboard and hardware function tables. Later a new method was introduced whereby a large number of decimal switches spread over three “function tables” were treated as a read only memory, into which program code and constant data could be manually dialled. Other modifications were made during the early 1950s. ENIAC was finally switched off in 1955.
BINAC (Northrop Aircraft Company, February 1949). This was a stored-program computer working in 1949. BINAC’s final state has been subject to questions and there are some doubts about whether it was ever fully operational – [ref. 27].
EDSAC (University of Cambridge, May 1949). This was a fully-functional stored-program computer which was first demonstrated on 6th May 1949. It came into regular service in the University’s Mathematical Laboratory in January 1950. The document entitled Preparation of Programmes for the EDSAC was published as an internal report in September 1950. Enhancements such as a modifier register and an experimental magnetic tape deck followed in the next few years.
Descriptions of the above six machines are readily available on the web. Using the previous definition of a stored-program computer as being a general-purpose machine which holds both instructions and data in a read/write memory, here is a summary how these six computers compare with the Manchester SSEM (Baby).

 Computer & date of first operation   Stored program?   General purpose?   Fully operational? 
Z3, 1941 No Possibly Yes
ABC, 1942 No No Some doubts
COLOSSUS, 1943 No No Yes
ENIAC, 1945 then 1948 Primitive, read only Possibly Yes
BINAC, 1949 Yes Yes Some doubts
EDSAC, 1949 Yes Yes Yes
Manchester Baby, 1948 Yes Yes Yes

20. Candidates for the first commercially-produced stored-program computer to be marketed as a standard product and delivered to a customer include the following four machines:
Zuse Z4 was delivered to the Institute for Applied Mathematics at ETH Zurich on 11th July 1950. However, it was not a stored-program computer: its program of instructions was held on perforated 35mm film stock. Zuse KG, founded in 1949 with five employees, was the first computer manufacturing company in Germany. It is believed that only one Z4 computer was sold.
ERA Atlas 1. This stored-program computer was the result of a classified contract known as Task 13 placed by the US Navy’s Communications Supplementary Activities, Washington (CSAW) with the company Engineering Research Associates (ERA). The company, founded in January 1946, was staffed by CSAW codebreaking colleagues. Its premises in St Paul, Minnesota became part of the classified Naval Computing Machine Laboratory. The ERA Atlas was delivered in secret to Washington on 8th December 1950, was operational before Christmas and proved very reliable. It was the first general-purpose computer to be installed in any SIGINT establishment, though it initially lacked programmable input facilities. ERA subsequently wished to sell ATLAS I commercially as the ERA 1101. Permission was given by CSAW and the ERA 1101 was publicly announced in December 1951. However, the company experienced financial difficulties and was bought in 1952 by Remington Rand. More on the ERA Atlas and its comparison in price and performance with the Ferranti Mark I* is given in Chapter 10 of: Early computing in Britain: Ferranti Ltd. and government funding, 1948 – 1958. Simon Lavington. Published by Springer, 2019. See especially Chapter 10: GCHQ Cheltenham’s Mark I*.
UNIVAC I. This was most probably the first commercially produced computer to have been sold in the USA. The first sale, to the Census Bureau, was agreed on 31st March 1951. However the first UNIVAC off the production line was kept back for demonstration purposes and delivery to the Census Bureau did not take place until the end of 1952. The first UNIVAC I to have been delivered to a customer was the second production machine, which went to the Pentagon in June 1952.
LEO I. The central design of LEO was based on the Cambridge EDSAC computer, but with additional storage and punched card input/output equipment to cope with the requirements of commercial data-processing applications. Magnetic tapes were originally planned but these failed to materialise so punched cards were the only bulk storage provided. LEO I was developed in-house by the catering company J. Lyons & Co., to support a range of in-house business applications. The first job, the valuation of the weekly output of bread and cakes from Lyons' bakeries, ran on 5th September 1951. Other successful applications followed. In 1954 Lyons formed LEO Computers Ltd to manufacture computers. The first LEO II was delivered in May 1957. LEO I has sometimes been described as “the world’s first business computer”.

Descriptions of the above four machines are readily available on the web. Using the definition of a commercially-available stored-program computer given previously, it is seen that none of these four pre-date the Ferranti Mark I. Here is a summary.

 Computer & date of first delivery to a customer   Stored program?   Produced for the open Market?    Number sold  
Z4, July 1950 No Possibly 1
ERA Atlas 1, Dec. 1950 Yes No 1 (+?)
UNIVAC I, June 1952 Yes Yes Approx. 46
LEO I, (Sept. 1951) Yes No none
Ferranti Mark I, Feb. 1951 Yes Yes 9 incl. Mark I*

21. Early computing in Britain: Ferranti Ltd. and government funding, 1948 – 1958. Simon Lavington. Published by Springer, 2019. The influence of Max Newman, Jack Good and A M Uttley (TRE) at Manchester is analysed in Appendix 1: Baby’s conception: the back story.

22. T. Kilburn, D.B.G. Edwards, M.J. Lanigan, F.H. Sumner, One-level storage system. IRE Trans. EC-11, April 1962, pp 223-235.

23. Early computing in Britain: Ferranti Ltd. and government funding, 1948 – 1958. Simon Lavington. Published by Springer, 2019. See especially Appendix 2.

24(a). A system design proposal: T Kilburn, D Morris, J S Rohl and F H Sumner. In Information Processing 1968, Vol 2, pages 806-811, published by North Holland, 1969.

24 (b). The MU5 computer system: Derrick Morris and Roland Ibbett. Published by Macmillan, 1979. ISBN: 0-333-25749-9.

25 (a). Copeland, B J. The Manchester Computer: A Revised History Part 1: The Memory. IEEE Annals of the History of Computing 33, no. 1 (Jan-Mar 2011): pages 4 to 21.

25 (b). Copeland, B J. The Manchester Computer: A Revised History Part 2: The Baby computer. IEEE Annals of the History of Computing 33, no. 1 (Jan-Mar 2011): pages 22 to 37.

25 (c). David Anderson. Max Newman: forgotten man of early British computing. Commun. ACM 56, 5 (May 2013), pages 29–31.

25 (d). David Anderson. Was the Manchester Baby conceived at Bletchley Park? In Proceedings of the 2004 international conference on Alan Mathison Turing: a celebration of his life and achievements (Turing'04). BCS Learning & Development Ltd., Swindon.

26. Alan Turing and his contemporaries: building the world’s first computers. Simon Lavington (ed.), Published by the British Computer Society, 2012. ISBN: 978-1-90612-490-8.

27. Nancy Stern. The BINAC: a case study in the history of technology. Annals of the history of computing, Vol. 1 number 1 July 1979, pages 9 – 20.

28. The Royal Society: Meeting of Government Grant Board B on 12th February 1946. Enclosure G: Application for “a grant to start a calculating machine laboratory at the University of Manchester”, from Professor M H A Newman. Enclosure G is a copy of the grant-application letter from Professor Newman dated 28th January 1946. Here are some salient points extracted from Professor Newman’s letter.
(a). “The search for standard logical parts, out of which instructions could be built up, has already brought the ideas and methods of symbolic logic and abstract algebra into the field, and it is clear that they will play a prominent part in the development. … There is opportunity for the use of machinery within mathematics itself. For example, a hypothesis equivalent to the Riemann Zeta Hypothesis could be tested for a certain range of a positive integral values ….
(b). “The University unit would of course work in close collaboration with the NPL unit …. The Post Office Research Station at Dollis Hill, with which I was fortunate in making contact during the war, are also interested in the project …. Dr Radley [ W. Gordon Radley, the Dollis Hill Director] would also take on the manufacture of apparatus in the Post Office factory. …. A circuit-designing engineer [recruited at Manchester] should spend some weeks at Dollis Hill, gaining knowledge of the known techniques in the field”.
(c).“Evidently the success of the enterprise would hang largely on the appointment of the designing engineer [at Manchester]. Although he would not be expected to provide the main ideas for projects, he would need a rare combination of wide practical experience in circuit design, with a thorough understanding of the abstract ideas involved”.
(d). “The object of the laboratory would be to produce pilot models, not to run machines on a production basis. Once a machine was running well, the time would have come to start a new one. It is to be expected therefore that the extra constructional mechanics [on loan from Dollis Hill] would be needed every eighteen months or so”.
(e). [In summary]. “The project is for a laboratory to investigate electronic machines to deal with mathematical problems of general type”.

Public outreach.

29. The 1949 BBC Newsreel clip is here:
The sequence is titled Lancashire, indicating to those whose geography is hazy that the City of Manchester was at the time in the county of Lancashire (it is now a Metropolitan County in its own right).

30. Here is a Google-sponsored film, made in June 2013 for the Manchester Baby’s 65th anniversary. It features interviews with the then only two survivors of Kilburn’s team, Geoff Tootill (ex-TRE) and Dai Edwards who joined in September 1948 as a research student. Also interviewed is Chris Burton, formerly of Ferranti, who led the team building a working reconstruction of the Baby computer for the 50th anniversary in 1998, and Simon Lavington who first joined Tom Kilburn’s group in 1962. The video is here:
At the time of writing this Milestone proposal (February 2021), the reconstructed Baby computer is still giving working demonstrations to the public (Covid permitting) at the Museum of Science and Industry in Manchester.

31. Apart from the authentic sense given by the reconstructed Baby computer, no original bits of Baby hardware survive. Units of only one commercially-produced derivative survive. These come from the Ferranti Mark I* that was delivered to the aerospace company A V Roe (Avro) in 1956 and taken out of service in 1965. This machine was initially stored in Leicester Industrial Museum’s Abbey Pumping Station. At the time of writing (February 2021), hardware units from this computer are displayed or stored at these locations;

The Computer History Museum, Mountain View, California;
The Science Museum, South Kensington, London;
The National Museums Scotland, Edinburgh;
The Museum of Science and Industry, Manchester;
The National Museum of Computing, Bletchley Park;
The Department of Computer Science, University of Manchester.

Supporting materials:

1. University of Manchester letter of 29th September 2020 allowing for placement of an IEEE Milestone bronze plaque on the outside of the Coupland I Building, Bridgeford Street, Manchester, where the historic first demonstration took place.
2. Since the references cited in this Proposal are either copyright encumbered or lack the rights to post the documents have been provided by email to

Supporting materials