EDVAC was one of the earliest electronic computers. Unlike its predecessor the ENIAC, it was binary rather than decimal, was designed to be a stored-program computer. ENIAC inventors John Mauchly and J. Presper Eckert proposed the EDVAC's construction in August 1944. A contract to build the new computer was signed in April 1946 with an initial budget of US$100,000. EDVAC was delivered to the Ballistics Research Laboratory in 1949; the Ballistic Research Laboratory became a part of the US Army Research Laboratory in 1942. Functionally, EDVAC was a binary serial computer with automatic addition, multiplication, programmed division and automatic checking with an ultrasonic serial memory capacity of 1,000 34-bit words. EDVAC's average addition time was 864 microseconds and its average multiplication time was 2,900 microseconds. ENIAC inventors John Mauchly and J. Presper Eckert proposed EDVAC's construction in August 1944, design work for EDVAC commenced before ENIAC was operational; the design would implement a number of important architectural and logical improvements conceived during the ENIAC's construction and would incorporate a high-speed serial-access memory.
Like the ENIAC, the EDVAC was built for the U. S. Army's Ballistics Research Laboratory at the Aberdeen Proving Ground by the University of Pennsylvania's Moore School of Electrical Engineering. Eckert and Mauchly and the other ENIAC designers were joined by John von Neumann in a consulting role. A contract to build the new computer was signed in April 1946 with an initial budget of US$100,000; the contract named the device the Electronic Discrete Variable Automatic Calculator. The final cost of EDVAC, was similar to the ENIAC's, at just under $500,000; the EDVAC was a binary serial computer with automatic addition, multiplication, programmed division and automatic checking with an ultrasonic serial memory capacity of 1,000 44-bit words. Physically, the computer comprised the following components: a magnetic tape reader-recorder a control unit with an oscilloscope a dispatcher unit to receive instructions from the control and memory and direct them to other units a computational unit to perform arithmetic operations on a pair of numbers at a time and send the result to memory after checking on a duplicate unit a timer a dual memory unit consisting of two sets of 64 mercury acoustic delay lines of eight words capacity on each line three temporary tanks each holding a single wordEDVAC's average addition time was 864 microseconds and its average multiplication time was 2,900 microseconds.
Time for an operation depended on memory access time, which varied depending on the memory address and the current point in the serial memory's recirculation cycle. The computer had 6,000 vacuum tubes and 12,000 diodes, consumed 56 kW of power, it weighed 17,300 pounds. The full complement of operating personnel was thirty people per eight-hour shift. John Von Neumann's famous EDVAC monograph, First Draft of a Report on the EDVAC, proposed the main enhancement to its design that embodied the principle "stored-program" concept that we now call the Von Neumann architecture; this was the storing of the program in the same memory as the data. The British computers EDSAC at Cambridge and the Manchester Baby were the first working computers that followed this design, and it has been followed by the great majority of all computers made since. Having the program and data in different memories is now called the Harvard architecture to distinguish it. EDVAC was delivered to the Ballistics Research Laboratory in 1949.
After a number of problems had been discovered and solved, the computer began operation in 1951 although only on a limited basis. In 1952 it was running over 7 hours a day. By 1957 EDVAC was running over 20 hours a day with error-free run time averaging 8 hours. EDVAC received a number of upgrades including punch-card I/O in 1954, extra memory in slower magnetic drum form in 1955, a floating-point arithmetic unit in 1958. EDVAC ran until 1962 when it was replaced by BRLESC. List of vacuum tube computers Moore School of Electrical Engineering. A Functional Description of the EDVAC: A Report of Development Work under Contract W36-034-ORD-7593 with the Ordnance Department, Department of the Army. Philadelphia: University of Pennsylvania. A complete technical description of EDVAC's original structure and operation in 1949. Viewable online. Oral history interview with J. Presper Eckert, Charles Babbage Institute, University of Minnesota. Oral history interview with Carl Chambers, Charles Babbage Institute, University of Minnesota.
Oral history interview with Irven A. Travis, Charles Babbage Institute, University of Minnesota. Oral history interview with S. Reid Warren, Charles Babbage Institute, University of Minnesota. Oral history interview with Frances E. Holberton, Charles Babbage Institute, University of Minnesota
Birkbeck, University of London
Birkbeck, University of London, is a public research university located in Bloomsbury London, a constituent college of the federal University of London. Established in 1823 as the London Mechanics' Institute by its founder, Sir George Birkbeck, its supporters, Jeremy Bentham, J. C. Hobhouse and Henry Brougham, Birkbeck has been one of the few institutions to specialise in evening higher education. Birkbeck's main building is based in the Bloomsbury zone of Camden, in Central London, alongside a number of institutions in the same borough. In partnership with University of East London, Birkbeck has an additional large campus in Stratford, next to the Theatre Royal. Birkbeck offers over 200 undergraduate and postgraduate programmes that can be studied either part-time or full-time, though nearly all lectures are given in the evening. Birkbeck's academic activities are organised into five constituent faculties which are subdivided into nineteen departments, it offers many continuing education courses leading to certificates and diplomas, foundation degrees, short courses.
Research at Birkbeck in 11 subject areas is rated as ‘internationally excellent’ and ‘world leading’ while over 90 percent of Birkbeck academics are research-active. Birkbeck, being part of the University of London, shares the University's academic standards and awards University of London degrees. In common with the other University of London colleges, Birkbeck has secured its own independent degree awarding powers, which were confirmed by the Privy Council in July 2012; the quality of degrees awarded by Birkbeck was confirmed by the UK Quality Assurance Agency following institutional audits in 2005 and 2010. Birkbeck has been shortlisted by the Times Higher Education Awards as University of the Year. Birkbeck is a member of academic organisations such as the Association of Commonwealth Universities and the European University Association; the university's Centre for Brain Function and Development was awarded The Queen's Anniversary Prize for its brain research in 2005. Birkbeck has produced many notable alumni in the fields of science, politics, literature, media and drama.
Alumni include four Nobel laureates, numerous political leaders, members of the Parliament of the United Kingdom, a British prime minister among its former students and faculty. In 1823, Sir George Birkbeck, a physician and graduate of the University of Edinburgh and an early pioneer of adult education, founded the "London Mechanics' Institute" at a meeting at the Crown and Anchor Tavern on the Strand. More than two thousand people attended; however the idea was not universally popular and some accused Birkbeck of "scattering the seeds of evil."In 1825, two years the institute moved to the Southampton Buildings on Chancery Lane. In 1830, the first female students were admitted. In 1858, changes to the University of London's structure resulting in an opening up of access to the examinations for its degree; the Institute became the main provider of part-time university education. In 1866, the Institute changed its name to the Birkbeck Scientific Institution. In 1885, Birkbeck moved to the Breams Building, on Fetter Lane, where it would remain for the next sixty-seven years.
In 1904, Birkbeck Students' Union was established In 1907, Birkbeck's name was shortened to "Birkbeck College". In 1913, a review of the University of London recommended that Birkbeck become a constituent college, although the outbreak of the First World War delayed this until 1920; the Royal Charter was granted in 1926. In 1921, the college's first female professor, Dame Helen Gwynne-Vaughan, began teaching botany. Other distinguished faculty in the inter-war years included Nikolaus Pevsner, J. D. Bernal, Cyril Joad. During the Second World War, Birkbeck was the only central University of London college not to relocate out of the capital. In 1941, the library suffered a direct hit during The Blitz but teaching continued. During the war the College organised lunch time extramural lectures for the public given by, among others, Joad and Harold Nicolson. In 1952, the college moved to its present location in Malet Street. In 2002, the college was re-styled University of London. In 2003, following a major redevelopment, its Malet Street building was reopened by the Chancellor of the University of London, HRH The Princess Royal.
In 2006, Birkbeck announced that it had been granted £5 million by the Higher Education Funding Council for England to expand its provision into east London, working with the University of East London. The partnership is called Birkbeck Stratford. Birkbeck is one of the largest colleges of the University of London not to award its own degrees. Although it has held its own degree awarding powers since 2012, Birkbeck has chosen to hold these in reserve, preferring to award University of London degrees. In 1876, the London Society for the Extension of University Education was founded, boosting the aims of encouraging working people to undertake higher education. In 1988, the Department of Extra-Mural Studies of the University of London was incorporated into Birkbeck, becoming at first the Centre for Extramural Studies. In 1903, it became the Department of Extra-Mural Studies of the University of London and it was integrated into Birkbeck in 1988 as the School of Continuing Education. In 2009, the Faculty of Lifelong Learning was incorporated into the main College structure.
Birkbeck is principally located between Malet Street and Woburn Square in Bloomsbury, with a number of institutes, teaching hospitals, scientific laboratories on nearby streets. The Friends House is partially owned by Birkbeck Law School; the School of Arts, including the
Manchester Mark 1
The Manchester Mark 1 was one of the earliest stored-program computers, developed at the Victoria University of Manchester from the Manchester Baby. It was called the Manchester Automatic Digital Machine, or MADM. Work began in August 1948, the first version was operational by April 1949; the machine's successful operation was 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 be 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 quickly became a prototype on which the design of Ferranti's commercial version could be based. Development ceased at the end of 1949, 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 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, 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. In 1951, they started development work on Meg, the Mark 1's successor, which would include a floating point unit. In 1936, mathematician Alan Turing 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 could be written.
During the 1940s, Turing and others such as Konrad Zuse 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 who became 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's Baby, the world's first electronic stored-program computer, had 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, by running its first program on 21 June 1948. Early electronic computers were programmed by being rewired, or via plugs and patch panels, it could take several days for instance. Stored-program computers were being developed by other researchers, notably the National Physical Laboratory's Pilot ACE, Cambridge University's EDSAC, the US Army's EDVAC.
The Baby and the Mark 1 differed 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 with the aim of providing the university with a more realistic computing facility. 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. Lockspeiser was so impressed by what he saw that he initiated a government contract with the local firm of Ferranti 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, involved an estimated £35,000 per year. The Baby had been designed by the team of Frederic C. Williams, Tom Kilburn and Geoff Tootill. To develop the Mark 1 they were joined by D. B. G. Edwards and G. E. Thomas; 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, 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, working by October 1949.
The machine had a power consumption of 25 kilowatts. 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 incr
History of computing in the Soviet Union
The history of computing in the Soviet Union began during the late 1940s, when the country began to develop MESM at the Kiev Institute of Electrotechnology in Feofaniya. Initial ideological opposition to cybernetics in general was overcome during the Khrushchev era, computer production was encouraged. By the early 1970s, uncoordinated work by competing government ministries left the Soviet computer industry lacking common standards in peripherals and digital capacity which led to a significant technological lag behind Western producers; the Soviet government decided to abandon the development of original computer designs and encouraged the pirating of Western systems. Soviet industry lacked the technology to mass-produce computers with acceptable quality standards, locally-manufactured copies of Western hardware were unreliable; as personal computers spread to industries and offices in the West, the Soviet Union's technological lag increased. Nearly all Soviet computer manufacturers ceased operations after the breakup of the Soviet Union.
The few companies which survived into the 1990s used foreign components and never achieved large production volumes. In 1936, an analog computer known as a water integrator was designed by Vladimir Lukyanov, it was the world's first computer for solving partial differential equations. The Soviet Union began to develop digital computers after World War II; the first universally programmable electronic computer in continental Europe was created by a team of scientists directed by Sergey Lebedev at the Kiev Institute of Electrotechnology in Feofaniya. The computer, known as MESM, became operational in 1950; the MESM's vacuum tubes were obtained from radio manufacturers. The attitude of Soviet officials to computers was skeptical or hostile during the Stalinist era, government rhetoric portrayed cybernetics as a capitalist attempt to further undermine workers' rights; the Soviet weekly newspaper Literaturnaya Gazeta published a 1950 article critical of Norbert Wiener and his book, Cybernetics: Or Control and Communication in the Animal and the Machine, describing Wiener as one of the "charlatans and obscurantists whom capitalists substitute for genuine scientists".
After the publication of the article, his book was removed from Soviet research libraries. The first large-scale computer, the BESM-1, was assembled in Moscow at the Lebedev Institute of Precision Mechanics and Computer Engineering. Soviet work on computers was first made public at the Darmstadt Conference in 1955; as in the United States, early computers were intended for military calculations. Automatic data processing systems made their debut by the mid-1950s with the Minsk and Ural systems, both designed by the Ministry of Radio Technology; the Ministry of Instrument Making entered the computer field with the ASVT system, based on the PDP-8. The Strela computer, commissioned in December 1956, performed calculations for Yuri Gagarin's first manned spaceflight; the Strela was designed by Special Design Bureau 245 of the Ministry of Instrument Making. Strela chief designer Y. Y. Bazilevsky received the Hero of Socialist Labor title for his work on the project. Setun, an experimental ternary computer, was designed and manufactured in 1959.
The Khrushchev Thaw relaxed ideological limitations, by 1961 the government encouraged the construction of computer factories. The Mir-1, Mir-2 and Mir-3 computers were produced at the Kiev Institute of Cybernetics during the 1960s. Victor Glushkov began his work on OGAS, a real-time, hierarchical computer network, in the early 1960s, but the project was never completed. Soviet factories began manufacturing transistor computers during the early years of the decade. At that time, ALGOL was the most common programming language in Soviet computing centers. ALGOL 60 was used with a number including ALGAMS, MALGOL and Alpha. ALGOL remained the most popular language for university instruction into the 1970s; the MINSK-2 was a solid-state digital computer that went into production in 1962, the Central Intelligence Agency attempted to obtain a model. The BESM-6, introduced in 1965, performed at about 800 KIPS on the Gibson Mix benchmark—ten times greater than any other serially-produced Soviet computer of the period, similar in performance to the CDC 3600.
From 1968 to 1987, 355 BESM-6 units were produced. With instruction pipelining, memory interleaving and virtual address translation, the BESM-6 was advanced for the era; the Ministry of the Electronics Industry was established in 1965, ending the Ministry of Radio Technology's primacy in computer production. The following year, the Soviet Union signed a cooperation agreement with France to share research in the computing field after the United States prevented France from purchasing a CDC 6600 mainframe. In 1967, the Unified System of Electronic Computers project was launched to create a general-purpose computer with the other Comecon countries. Soyuz 7K-L1 was the first Soviet piloted spacecraft with an onboard digital computer, the Argon-11S. Construction of the Argon-11S was completed in 1968 by the Scientific Research Institute of Electronic Machinery. According to Piers Bizony, lack of computing power was a factor in the failure of the Soviet manned lunar program. By the early 1970s, the lack of common standards in peripherals and digital capacity led to a significant technological lag behind Western producers.
Hardware limitations forced Soviet programmers to write programs in machine code until the early 1970s. Users were expected to repair their own hardware.
The Manchester Baby known as the Small-Scale Experimental Machine, was the world's first electronic stored-program computer. It was built at the Victoria University of Manchester, England, by Frederic C. Williams, Tom Kilburn, Geoff Tootill, ran its first program on 21 June 1948; the machine was not intended to be a practical computer, but was instead designed as a testbed for the Williams tube, the first random-access computer memory. Although considered "small and primitive" by the standards of its own time, it was nonetheless the first working machine to contain all the elements essential to a modern electronic computer; as soon as the Baby had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1. The Mark 1 in turn became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer; the Baby had a memory of 32 words. As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation.
The first of three programs written for the machine calculated the highest proper divisor of 218, an algorithm that would take a long time to execute—and so prove the computer's reliability—by testing every integer from 218 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for 52 minutes before reaching the correct answer of 131,072, after the Baby had performed 3.5 million operations. The first design for a program-controlled computer was Charles Babbage's Analytical Engine in the 1830s. A century in 1936, mathematician Alan Turing published his description of what became known as a Turing machine, a theoretical concept intended to explore the limits of mechanical computation. Turing was not imagining a physical machine, but a person he called a "computer", who acted according to the instructions provided by a tape on which symbols could be read and written sequentially as the tape moved under a tape head. Turing proved that if an algorithm can be written to solve a mathematical problem a Turing machine can execute that algorithm.
Konrad Zuse's Z3 was the world's first working programmable automatic computer, with binary digital arithmetic logic, but it lacked the conditional branching of a Turing machine. On 12 May 1941, it was presented to an audience of scientists of the Deutsche Versuchsanstalt für Luftfahrt in Berlin; the Z3 stored its program on an external tape. The Colossus of 1943 was the first electronic computing device, but it was not a general-purpose machine; the ENIAC was the first machine, both electronic and general purpose. It was Turing complete, with conditional branching, programmable to solve a wide range of problems, but its program was held in the state of switches in patchcords, not in memory, it could take several days to reprogram. Researchers such as Turing and Zuse investigated the idea of using the computer's memory to hold the program as well as the data it was working on, it was mathematician John von Neumann who wrote a distributed paper describing that computer architecture, still used in all computers.
The construction of a von Neumann computer depended on the availability of a suitable memory device on which to store the program. During the Second World War researchers working on the problem of removing the clutter from radar signals had developed a form of delay line memory, the first practical application of, the mercury delay line, developed by J. Presper Eckert. Radar transmitters send out regular brief pulses of radio energy, the reflections from which are displayed on a CRT screen; as operators are interested only in moving targets, it was desirable to filter out any distracting reflections from stationary objects. The filtering was achieved by comparing each received pulse with the previous pulse, rejecting both if they were identical, leaving a signal containing only the images of any moving objects. To store each received pulse for comparison it was passed through a transmission line, delaying it by the time between transmitted pulses. Turing joined the National Physical Laboratory in October 1945, by which time scientists within the Ministry of Supply had concluded that Britain needed a National Mathematical Laboratory to co-ordinate machine-aided computation.
A Mathematics Division was set up at the NPL, on 19 February 1946 Alan Turing presented a paper outlining his design for an electronic stored-program computer to be known as the Automatic Computing Engine. This was one of several projects set up in the years following the Second World War with the aim of constructing a stored-program computer. At about the same time, EDVAC was under development at the University of Pennsylvania's Moore School of Electrical Engineering, the University of Cambridge Mathematical Laboratory was working on EDSAC; the NPL did not have the expertise to build a machine like ACE, so they contacted Tommy Flowers at the General Post Office's Dollis Hill Research Laboratory. Flowers, the designer of Colossus, the world's first programmable electronic computer, was committed elsewhere and was unable to take part in the project, although his team did build some mercury delay lines for ACE; the Telecommunications Research Establishment was approached for assistance, as was Maurice Wilkes at the University of Cambridge Mathematical Laboratory.
The government department respon
The IBM Selective Sequence Electronic Calculator was an electromechanical computer built by IBM. Its design was started in late 1944, it operated from January 1948 to August 1952, it had many of the features of a stored-program computer and was the first operational machine able to treat its instructions as data, but it was not electronic. Although the SSEC proved useful for several high-profile applications it soon became obsolete; as the last large electromechanical computer built, its greatest success was the publicity it provided for IBM. During World War II, International Business Machines Corporation funded and built an Automatic Sequence Controlled Calculator for Howard H. Aiken at Harvard University; the machine, formally dedicated in August 1944, was known as the Harvard Mark I. The President of IBM, Thomas J. Watson, Sr. did not like Aiken's press release that gave no credit to IBM for its funding and engineering effort. Watson and Aiken decided to go their separate ways, IBM began work on a project to build their own larger and more visible machine.
Astronomer Wallace John Eckert of Columbia University provided specifications for the new machine. Francis "Frank" E. Hamilton supervised both construction of the ASCC as well as its successor. Robert Rex Seeber, Jr. was hired away from the Harvard group, became known as the chief architect of the new machine. Modules were manufactured in IBM's facility at Endicott, New York, under Director of Engineering John McPherson after the basic design was ready in December 1945; the February 1946 announcement of the electronic ENIAC energized the project. The new machine, called the IBM Selective Sequence Electronic Calculator, was ready to be installed by August 1947. Watson called such machines calculators because computer referred to humans employed to perform calculations and he wanted to convey the message that IBM's machines were not designed to replace people. Rather they were designed to help people, by relieving them of drudgery.. The SSEC was installed on three sides of a room on the ground floor of a building near IBM's headquarters at 590 Madison Avenue in New York City, behind a large window where it was visible to people passing by on the busy street.
The space had been occupied by a women's shoe store. The noisy SSEC was sometimes called Poppa by the viewing pedestrians, it was dedicated and first demonstrated to the public on January 27, 1948. A. Wayne Brooke served as the chief electronic engineer for the machine's operation starting in 1950. Herb Grosch, the second person with a Ph. D. hired by IBM, was one of its first programmers. Another early programmer was Edgar "Ted" Codd. Elizabeth "Betsy" Stewart was chief operator, appeared in publicity photos; the SSEC was an unusual hybrid of electromechanical relays. 12,500 vacuum tubes were used in the arithmetic unit and its eight registers, which had an access time of less than one millisecond. About 21,400 relays were used for control and 150 lower-speed registers, with an access time of 20 milliseconds; the relay technology was similar to the ASCC, based on technology invented by Clair D. Lake; the arithmetic logic unit of the SSEC was a modified IBM 603 electronic multiplier, designed by James W. Bryce.
The bulky tubes were military surplus radar technology. The memory was organized as signed 19-digit decimal numbers. Multiplication was computed with 14 digits in each factor. Most of the quoted 400,000 digit capacity was in the form of reels of punched paper tape. Addition took 285 microseconds and multiplication 20 milliseconds, making arithmetic operations much faster than the Harvard Mark I. Data that had to be retrieved was held in electronic circuits. A chain hoist was needed to lift the heavy reels of paper into place; the machine read instructions or data from 30 paper tape readers connected to three punches, another a table look-up unit consisted of another 36 paper tape readers. A punched card reader was used to load data, results were produced on punched cards or high-speed printers; the 19-digit word was stored on the card stock tape or registers in binary coded decimal, resulting in 76 bits, with two extra bits for indicating positive or negative sign and parity, while the two side rows were used for sprockets.
The familiar 80 columns of IBM punched card technology were recorded sideways as one column of the tape. Using well-tested technology, the SSEC's calculations were accurate and precise for its time, but one early programmer, John Backus, said "you had to be there the entire time the program was running, because it would stop every three minutes, only the people who had programmed it could see how to get it running again”. ENIAC co-designer J. Presper Eckert called it "some big monstrosity over there that I don't think worked right". Seeber had designed the SSEC to treat instructions as data, so they could be modified and stored under program control. IBM filed a patent based on the SSEC on January 19, 1949, upheld as supporting the machine's stored program ability; each instruction could take input from any source store the result in any destination, gave the address of the next instruction, which could be any source. This made it powerful in theory. However, in practice instructions were stored on paper tape, resulting in an overall
A plugboard, or control panel, is an array of jacks, or sockets, into which patch cords can be inserted to complete an electrical circuit. Control panels were used to direct the operation of some unit record equipment. Plugboards were used on some cipher machines, some early computers. Main article: Unit record equipment The earliest machines were hard wired for specific applications. Control panels were introduced in 1906 for the Hollerith Type 1 Tabulator. Removable control panels were introduced with the Hollerith type 3-S tabulator in the 1920s. Applications could be wired on separate control panels, inserted into tabulators as needed. Removable control panels came to be used in all unit record machines where the machines use for different applications required rewiring. IBM removable control panels ranged in size from 6 1/4" by 10 3/4" to one to two feet on a side and had a rectangular array of hubs. Plugs at each end of a single-conductor patch cord were inserted into hubs, making a connection between two contacts on the machine when the control panel was placed in the machine, thereby connecting an emitting hub to an accepting or entry hub.
For example, in a card duplicator application a card column reading hub might be connected to a punch magnet entry hub. It was a simple matter to copy some fields to different columns, ignore other columns by suitable wiring. Tabulator control panels could require dozens of patch cords for some applications. Tabulator functions were implemented with both mechanical and electrical components. Control panels simplified the changing of electrical connections for different applications, but changing most tabulator's use still required mechanical changes; the IBM 407 was the first IBM tabulator. For most machines with control panels, from collators, interpreters, to the IBM 407, IBM manuals describe the control panel as "directing" or "automatic operation was obtained by...". The control panels of calculators, such as the IBM 602 and IBM 604, that specified a sequence of operations, were described as being programs. Unit record equipment was configured for a specific task using a removable control panel.
The electrical connections of the various components in the unit record machine were presented on the panel, connections between them were determined by the wiring, with the actual connections made when the panel was inserted into the machine and locked in place. The closest modern analog is the field-programmable gate array, where a fixed number of logic components are made available and their interconnection wiring is determined by the user. Wiring a unit record control panel required knowledge of the machine's components and their timing constraints; the components of most unit record machines were synchronized to a rotating shaft. One rotation represented a single machine cycle, during which punched cards would advance from one station to the next, a line might be printed, a total might be printed and so on; the cycles were divided into points according to when the rows on a punched card would appear under a read or punch station. On most machines, cards were fed face down, 9-edge first.
Thus the first point in a card cycle would the second 8 time and so on to 0-time. The times from 9 to 0 were known as digits; these would be followed by 11 time and 12 time known as zones. In a read station, a set of 80 spring wire brushes pressed against one for each column; when a hole passed under the brush, the brush would make contact with a conductive surface beneath the card, connected to an electrical power source and an electrical pulse, an impulse in IBM terminology, would be generated. Each brush was connected to an individual hub on the control panel, from which it could be wired to another hub, as needed; the action caused by an impulse on a wire depended on when in the cycle it occurred, a simple form of time division multiplexing. Thus an impulse that occurred during 7-time on a wire connected to the column 26 punch magnet would punch a hole in row 7 of column 26. An impulse on the same wire that occurred at 4-time would punch a 4 in column 26. Impulses timed in this way came from read brushes that detected holes punched in cards as they passed under the brushes, but such pulses were emitted by other circuits, such as counter outputs.
Zone impulses and digit impulses were both needed for alphanumeric printing. They could both be sent on a single wire separated out by relay circuits based on the time within a cycle; the control panel for each machine type presented entry hubs in logical arrangements. In many places, two or more adjacent common hubs, would be connected, allowing more than one wire to be connected to that exit or entry. A few groups of hubs were not connected to any internal circuits; these bus hubs could be used to connect multiple wires. Small connector blocks called wire splits were available to join three or four wires together, above the control panel. Several are visible in the photo of an IBM 402 panel; the capabilities and sophistication of unit record machine components evolved over the first half of the 20th century and were specific to