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The Manchester Mark 1 was one of the earliest
stored-program computer A stored-program computer is a computer that stores program instructions in electronically or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechanisms. The definition ...
s, developed at the Victoria University of Manchester,
England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...
from the Manchester Baby (operational in June 1948). 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. The machine's successful operation was widely reported in the British press, which used the phrase "electronic brain" in describing it to their readers. 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. The Mark 1 was to provide a computing resource within the university, to allow researchers to gain experience in the practical use of computers, but it very quickly also became a prototype on which the design of
Ferranti Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index. The firm was known ...
's commercial version could be based. Development ceased at the end of 1949, and the machine was scrapped towards the end of 1950, replaced in February 1951 by a Ferranti Mark 1, the world's first commercially available general-purpose electronic computer. 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 and 702 as well as the Ferranti Mark 1. The chief designers, Frederic C. Williams and
Tom Kilburn Tom Kilburn (11 August 1921 – 17 January 2001) was an English mathematician and computer scientist. Over the course of a productive 30-year career, he was involved in the development of five computers of great historical significance. With ...
, concluded from their experiences with the Mark 1 that computers would be used more in scientific roles than in pure mathematics. In 1951, they started development work on
Meg Meg is a feminine given name, often a short form of Megatron, Megan, Megumi (Japanese), etc. It may refer to: People * Meg (singer), a Japanese singer *Meg Cabot (born 1967), American author of romantic and paranormal fiction * Meg Burton Cahill ...
, the Mark 1's successor, which would include a floating point unit. It was also called the Manchester Automatic Digital Machine, or MADM.


Background

In 1936, mathematician
Alan Turing Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical ...
published a definition of a theoretical "universal computing machine", a computer which held its program on tape, along with the data being worked on. Turing proved that such a machine was capable of solving any conceivable mathematical problem for which an
algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
could be written. During the 1940s, Turing and others such as
Konrad Zuse Konrad Ernst Otto Zuse (; 22 June 1910 – 18 December 1995) was a German civil engineer, pioneering computer scientist, inventor and businessman. His greatest achievement was the world's first programmable computer; the functional program- ...
developed the idea of using the computer's own memory to hold both the program and data, instead of tape, but it was mathematician
John von Neumann John von Neumann (; hu, Neumann János Lajos, ; December 28, 1903 – February 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. He was regarded as having perhaps the widest c ...
who became widely credited with defining that stored-program computer architecture, on which the Manchester Mark 1 was based. The practical construction of a von Neumann computer depended on the availability of a suitable memory device. The
University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The university owns and operates majo ...
's Baby, the world's first electronic stored-program computer, had successfully demonstrated the practicality of the stored-program approach and of the Williams tube, an early form of computer memory based on a standard
cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a Phosphorescence, phosphorescent screen. The images may represent electrical waveforms (osci ...
(CRT), by running its first program on 21 June 1948. Early electronic computers were generally programmed by being rewired, or via plugs and patch panels; there was no separate program stored in memory, as in a modern computer. It could take several days to reprogram
ENIAC ENIAC (; Electronic Numerical Integrator and Computer) was the first programmable, electronic, general-purpose digital computer, completed in 1945. There were other computers that had these features, but the ENIAC had all of them in one pac ...
, for instance. Stored-program computers were also being developed by other researchers, notably the National Physical Laboratory's Pilot ACE,
Cambridge University , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...
's
EDSAC The Electronic Delay Storage Automatic Calculator (EDSAC) was an early British computer. Inspired by John von Neumann's seminal '' First Draft of a Report on the EDVAC'', the machine was constructed by Maurice Wilkes and his team at the Univer ...
, and the
US Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
's EDVAC. The Baby and the Mark 1 differed primarily in their use of Williams tubes as memory devices, instead of mercury delay lines. 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. In October 1948, UK Government Chief Scientist
Ben Lockspeiser Sir Ben Lockspeiser, KCB, FRS, MIMechE, FRAeS (9 March 1891 – 18 October 1990) was a British scientific administrator and the first President of CERN. Early life and education Lockspeiser was born at 7 President Street in the City of Lon ...
was given a demonstration of the prototype Mark 1 while on a visit to the University of Manchester. Lockspeiser was so impressed by what he saw that he immediately initiated a government contract with the local firm of
Ferranti Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index. The firm was known ...
to make a commercial version of the machine, the Ferranti Mark 1. In his letter to the company, dated 26 October 1948, Lockspeiser authorised the company to "proceed on the lines we discussed, namely, to construct an electronic calculating machine to the instructions of Professor F. C. Williams". From that point on, development of the Mark 1 had the additional purpose of supplying Ferranti with a design on which to base their commercial machine. The government's contract with Ferranti ran for five years from November 1948, and involved an estimated £35,000 per year (equivalent to £ per year in ).


Development and design

The Baby had been designed by the team of Frederic C. Williams,
Tom Kilburn Tom Kilburn (11 August 1921 – 17 January 2001) was an English mathematician and computer scientist. Over the course of a productive 30-year career, he was involved in the development of five computers of great historical significance. With ...
and Geoff Tootill. To develop the Mark 1 they were joined by two research students, D. B. G. Edwards and G. E. Thomas; work began in earnest in August 1948. The project soon had the dual purpose of supplying Ferranti with a working design on which they could base a commercial machine, the Ferranti Mark 1, and of building a computer that would allow researchers to gain experience of how such a machine could be used in practice. The first of the two versions of the Manchester Mark 1 – known as the Intermediary Version – was operational by April 1949. However, this first version lacked features such as the instructions necessary to programmatically transfer data between the main store and its newly developed magnetic backing store, which had to be done by halting the machine and manually initiating the transfer. These missing features were incorporated in the Final Specification version, which was fully working by October 1949. The machine contained 4,050 valves and had a power consumption of 25
kilowatts The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James W ...
. To increase reliability, purpose-built CRTs made by GEC were used in the machine instead of the standard devices used in the Baby. The Baby's 32-bit word length was increased to 40 bits. Each word could hold either one 40-bit number or two 20-bit program instructions. The main store initially consisted of two double-density Williams tubes, each holding two arrays of 32 x 40-bit words – known as
pages Page most commonly refers to: * Page (paper), one side of a leaf of paper, as in a book Page, PAGE, pages, or paging may also refer to: Roles * Page (assistance occupation), a professional occupation * Page (servant), traditionally a young mal ...
 – backed up by a magnetic drum capable of storing an additional 32 pages. The capacity was increased in the Final Specification version to eight pages of main store on four Williams tubes and 128 magnetic drum pages of backing store. The diameter drum,. (Reprint of Kilburn, Tom (1949). "The University of Manchester Universal High-Speed Digital Computing Machine". ''Nature'' 164). initially known as a magnetic wheel, contained a series of parallel magnetic tracks around its surface, each with its own read/write head. Each track held 2,560 bits, corresponding to two pages (2×32×40 bits). One revolution of the drum took 30  milliseconds, during which time both pages could be transferred to the CRT main memory, although the actual data transfer time depended on the latency, the time it took for a page to arrive under the read/write head. Writing pages to the drum took about twice as long as reading. The drum's rotational speed was synchronised to the main central processor clock, which allowed for additional drums to be added. Data was recorded onto the drum using a phase modulation technique still known today as
Manchester coding In telecommunication and data storage, Manchester code (also known as phase encoding, or PE) is a line code in which the encoding of each data bit is either low then high, or high then low, for equal time. It is a self-clocking signal with no DC ...
. The machine's
instruction set In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ...
was increased from the 7 of the Baby to 26 initially, including multiplication done in hardware. This increased to 30 instructions in the Final Specification version. Ten bits of each word were allocated to hold the instruction code. The standard instruction time was 1.8 milliseconds, but multiplication was much slower, depending on the size of the
operand In mathematics, an operand is the object of a mathematical operation, i.e., it is the object or quantity that is operated on. Example The following arithmetic expression shows an example of operators and operands: :3 + 6 = 9 In the above exam ...
. The machine's most significant innovation is generally considered to be its incorporation of index registers, commonplace on modern computers. The Baby had included two registers, implemented as Williams tubes: the accumulator (A) and the
program counter The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, i ...
(C). As A and C had already been assigned, the tube holding the two index registers, originally known as B-lines, was given the name B. The contents of the registers could be used to modify program instructions, allowing convenient iteration through an array of numbers stored in memory. The Mark 1 also had a fourth tube, (M), to hold the multiplicand and multiplier for a multiplication operation.


Programming

Of the 20 bits allocated for each program instruction, 10 were used to hold the instruction code, which allowed for 1,024 (210) different instructions. The machine had 26 initially, 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. On the Intermediary Version programs were input by key switches, and the output was displayed as a series of dots and dashes on a cathode-ray tube known as the output device, just as on the Baby from which the Mark 1 had been developed. However, the Final Specification machine, completed in October 1949, benefitted from the addition of a
teleprinter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Init ...
with a five-hole paper-tape reader and punch. Mathematician
Alan Turing Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical ...
, who had been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at the University of Manchester in September 1948, devised a
base 32 Base32 is the base-32 numeral system. It uses a set of 32 digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper ...
encoding scheme based on the standard
ITA2 The Baudot code is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII ...
5-bit teleprinter code, which allowed programs and data to be written to and read from paper tape. The ITA2 system maps each of the possible 32 binary values that can be represented in 5 bits (25) to a single character. Thus "10010" represents "D", "10001" represents "Z", and so forth. Turing changed only a few of the standard encodings; for instance, 00000 and 01000, which mean "no effect" and "linefeed" in the teleprinter code, were represented by the characters "/" and "@" respectively. Binary zero, represented by the forward slash, was the most common character in programs and data, leading to sequences written as "///////////////". One early user suggested that Turing's choice of a forward slash was a subconscious choice on his part, a representation of rain seen through a dirty window, reflecting Manchester's "famously dismal" weather. Because the Mark 1 had a 40-bit word length, eight 5-bit teleprinter characters were required to encode each word. Thus for example the binary word: would be represented on paper tape as ZDSLZWRF. The contents of any word in store could also be set via the teleprinter's keyboard, and output onto its printer. The machine worked internally in binary, but it was able to carry out the necessary decimal to binary and binary to decimal conversions for its input and output respectively. There was no
assembly language In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence b ...
defined for the Mark 1. 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. Data was read and written from the papertape punch under program control. 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 Mark 1 had no
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
; its only system software was a few basic routines for input and output. As in the Baby from which it was developed, and in contrast to the established mathematical convention, the machine's storage was arranged with the least significant digits to the left; thus a one was represented in five bits as "10000", rather than the more conventional "00001". Negative numbers were represented using
two's complement Two's complement is a mathematical operation to reversibly convert a positive binary number into a negative binary number with equivalent (but negative) value, using the binary digit with the greatest place value (the leftmost bit in big- endian ...
, as most computers still do today. In that representation, the value of the most significant bit denotes the sign of a number; positive numbers have a zero in that position and negative numbers a one. Thus the range of numbers that could be held in each 40-bit word was −239 to +239 − 1 (decimal: -549,755,813,888 to +549,755,813,887).


First programs

The first realistic program to be run on the Mark 1 was a search for Mersenne primes, in early April 1949, 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 The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The university owns and operates majo ...
, and the program was written by Kilburn and Tootill. Alan Turing later wrote an optimised version of the program, dubbed the Mersenne Express. The Manchester Mark 1 continued to do useful mathematical work until 1950, including an investigation of the
Riemann hypothesis In mathematics, the Riemann hypothesis is the conjecture that the Riemann zeta function has its zeros only at the negative even integers and complex numbers with real part . Many consider it to be the most important unsolved problem in p ...
and calculations in
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
.


Later developments

Tootill was temporarily transferred from the University of Manchester to Ferranti in August 1949, to continue work on the Ferranti Mark 1's design, and spent four months working with the company. The Manchester Mark 1 was dismantled and scrapped in August 1950, replaced a few months later by the first Ferranti Mark 1, the world's first commercially available general-purpose computer. Between 1946 and 1949, the average size of the design team working on the Mark 1 and its predecessor, the Baby, had been about four people. During that time 34 patents were taken out based on the team's work, either by the
Ministry of Supply The Ministry of Supply (MoS) was a department of the UK government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. A separate ministry, however, was responsible for airc ...
or by its successor, the National Research Development Corporation. In July 1949, IBM invited Williams to the United States on an all-expenses-paid trip to discuss the Mark 1's design. 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. 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. 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. Work began in 1951, and the resulting machine, which ran its first program in May 1954, was known as Meg, or the megacycle machine. It was smaller and simpler than the Mark 1, and much faster for maths problems.
Ferranti Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index. The firm was known ...
produced a version of Meg with the Williams tubes replaced by the more reliable core memory, marketed as the Ferranti Mercury.


Cultural impact

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. Lord
Louis Mountbatten Louis Francis Albert Victor Nicholas Mountbatten, 1st Earl Mountbatten of Burma (25 June 1900 – 27 August 1979) was a British naval officer, colonial administrator and close relative of the British royal family. Mountbatten, who was of German ...
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. 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. His purpose was to "debunk" the Manchester project. In his address he said: ''
The Times ''The Times'' is a British daily national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its current name on 1 January 1788. ''The Times'' and its sister paper '' The Sunday Times'' ( ...
'' reported on Jefferson's speech the following day, adding that Jefferson forecast that "the day would never dawn when the gracious rooms of the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
would be converted into garages to house these new fellows". This was interpreted as a deliberate slight to Newman, who had secured a grant from the society to continue the work of the Manchester team. 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. His article included an interview with Turing, who added:


See also

*
History of computing hardware The history of computing hardware covers the developments from early simple devices to aid calculation to modern day computers. Before the 20th century, most calculations were done by humans. The first aids to computation were purely mechan ...
* List of vacuum tube computers * Manchester computers


References


Notes


Citations


Bibliography

* * * * *


Further reading

*


External links


The Manchester Mark 1


in ''Resurrection'' (The Bulletin of the Computer Conservation Society) 1 (4), Summer 1992, {{featured article 1940s computers Early British computers One-of-a-kind computers Vacuum tube computers Computer-related introductions in 1949 Department of Computer Science, University of Manchester