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99-559: The advice taker was a hypothetical computer program , proposed by John McCarthy in his 1959 paper "Programs with Common Sense". It was probably the first proposal to use logic to represent information in a computer and not just as the subject matter of another program. It may also have been the first paper to propose common sense reasoning ability as the key to Artificial Intelligence . In his paper, McCarthy advocated: McCarthy justified his proposal as follows: Computer program A computer program in its human-readable form

198-507: A computer terminal (until the 1990s) to a graphical user interface (GUI) computer. Computer terminals limited programmers to a single shell running in a command-line environment . During the 1970s, full-screen source code editing became possible through a text-based user interface . Regardless of the technology available, the goal is to program in a programming language . Programming language features exist to provide building blocks to be combined to express programming ideals. Ideally,

297-462: A list of integers could be called integer_list . In object-oriented jargon, abstract datatypes are called classes . However, a class is only a definition; no memory is allocated. When memory is allocated to a class and bound to an identifier , it is called an object . Object-oriented imperative languages developed by combining the need for classes and the need for safe functional programming . A function, in an object-oriented language,

396-523: A stored-program computer loads its instructions into memory just like it loads its data into memory. As a result, the computer could be programmed quickly and perform calculations at very fast speeds. Presper Eckert and John Mauchly built the ENIAC. The two engineers introduced the stored-program concept in a three-page memo dated February 1944. Later, in September 1944, John von Neumann began working on

495-406: A Turing machine will ever halt. This paper has been called "easily the most influential math paper in history". Although Turing's proof was published shortly after Church's equivalent proof using his lambda calculus , Turing's approach is considerably more accessible and intuitive than Church's. It also included a notion of a 'Universal Machine' (now known as a universal Turing machine ), with

594-781: A ban) was used in cryptanalysis of the Lorenz cipher . Turing travelled to the United States in November 1942 and worked with US Navy cryptanalysts on the naval Enigma and bombe construction in Washington. He also visited their Computing Machine Laboratory in Dayton, Ohio . Turing's reaction to the American bombe design was far from enthusiastic: The American Bombe programme was to produce 336 Bombes, one for each wheel order. I used to smile inwardly at

693-503: A campaign in 2009, British prime minister Gordon Brown made an official public apology for "the appalling way [Turing] was treated". Queen Elizabeth II granted a pardon in 2013. The term " Alan Turing law " is used informally to refer to a 2017 law in the UK that retroactively pardoned men cautioned or convicted under historical legislation that outlawed homosexual acts. Turing left an extensive legacy in mathematics and computing which today

792-421: A central object of study in theory of computation . From September 1936 to July 1938, Turing spent most of his time studying under Church at Princeton University , in the second year as a Jane Eliza Procter Visiting Fellow . In addition to his purely mathematical work, he studied cryptology and also built three of four stages of an electro-mechanical binary multiplier . In June 1938, he obtained his PhD from

891-401: A color display and keyboard that was packaged in a single console. The disk operating system was programmed using IBM's Basic Assembly Language (BAL) . The medical records application was programmed using a BASIC interpreter. However, the computer was an evolutionary dead-end because it was extremely expensive. Also, it was built at a public university lab for a specific purpose. Nonetheless,

990-428: A cryptanalyst who worked with Turing, said of his colleague: In the first week of June each year he would get a bad attack of hay fever, and he would cycle to the office wearing a service gas mask to keep the pollen off. His bicycle had a fault: the chain would come off at regular intervals. Instead of having it mended he would count the number of times the pedals went round and would get off the bicycle in time to adjust

1089-540: A doctorate degree from Princeton University . During World War II , Turing worked for the Government Code and Cypher School at Bletchley Park , Britain's codebreaking centre that produced Ultra intelligence. He led Hut 8 , the section responsible for German naval cryptanalysis. Turing devised techniques for speeding the breaking of German ciphers , including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for

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1188-536: A little the same about me ... I know I must put as much energy if not as much interest into my work as if he were alive, because that is what he would like me to do. Turing's relationship with Morcom's mother continued long after Morcom's death, with her sending gifts to Turing, and him sending letters, typically on Morcom's birthday. A day before the third anniversary of Morcom's death (13 February 1933), he wrote to Mrs. Morcom: I expect you will be thinking of Chris when this reaches you. I shall too, and this letter

1287-509: A major contributor. The statements were English-like and verbose. The goal was to design a language so managers could read the programs. However, the lack of structured statements hindered this goal. COBOL's development was tightly controlled, so dialects did not emerge to require ANSI standards. As a consequence, it was not changed for 15 years until 1974. The 1990s version did make consequential changes, like object-oriented programming . ALGOL (1960) stands for "ALGOrithmic Language". It had

1386-548: A process. The interpreter then loads the source code into memory to translate and execute each statement . Running the source code is slower than running an executable . Moreover, the interpreter must be installed on the computer. The "Hello, World!" program is used to illustrate a language's basic syntax . The syntax of the language BASIC (1964) was intentionally limited to make the language easy to learn. For example, variables are not declared before being used. Also, variables are automatically initialized to zero. Here

1485-521: A profound influence on programming language design. Emerging from a committee of European and American programming language experts, it used standard mathematical notation and had a readable, structured design. Algol was first to define its syntax using the Backus–Naur form . This led to syntax-directed compilers. It added features like: Algol's direct descendants include Pascal , Modula-2 , Ada , Delphi and Oberon on one branch. On another branch

1584-466: A programming language should: The programming style of a programming language to provide these building blocks may be categorized into programming paradigms . For example, different paradigms may differentiate: Each of these programming styles has contributed to the synthesis of different programming languages . A programming language is a set of keywords , symbols , identifiers , and rules by which programmers can communicate instructions to

1683-489: A sensibility of such profundity and originality that one is filled with wonder and excitement. Alan Turing was such a genius, and those, like myself, who had the astonishing and unexpected opportunity, created by the strange exigencies of the Second World War, to be able to count Turing as colleague and friend will never forget that experience, nor can we ever lose its immense benefit to us. Hilton echoed similar thoughts in

1782-494: A syntax that would likely fail IBM's compiler. The American National Standards Institute (ANSI) developed the first Fortran standard in 1966. In 1978, Fortran 77 became the standard until 1991. Fortran 90 supports: COBOL (1959) stands for "COmmon Business Oriented Language". Fortran manipulated symbols. It was soon realized that symbols did not need to be numbers, so strings were introduced. The US Department of Defense influenced COBOL's development, with Grace Hopper being

1881-469: A technological improvement to refine the production of field-effect transistors (1963). The goal is to alter the electrical resistivity and conductivity of a semiconductor junction . First, naturally occurring silicate minerals are converted into polysilicon rods using the Siemens process . The Czochralski process then converts the rods into a monocrystalline silicon , boule crystal . The crystal

1980-562: A version of the central limit theorem . It was finally accepted on 16 March 1935. By spring of that same year, Turing started his master's course (Part III)—which he completed in 1937—and, at the same time, he published his first paper, a one-page article called Equivalence of left and right almost periodicity (sent on 23 April), featured in the tenth volume of the Journal of the London Mathematical Society . Later that year, Turing

2079-590: Is a genius". Between January 1922 and 1926, Turing was educated at Hazelhurst Preparatory School, an independent school in the village of Frant in Sussex (now East Sussex ). In 1926, at the age of 13, he went on to Sherborne School , an independent boarding school in the market town of Sherborne in Dorset, where he boarded at Westcott House. The first day of term coincided with the 1926 General Strike , in Britain, but Turing

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2178-542: Is an example computer program, in Basic, to average a list of numbers: Once the mechanics of basic computer programming are learned, more sophisticated and powerful languages are available to build large computer systems. Improvements in software development are the result of improvements in computer hardware . At each stage in hardware's history, the task of computer programming changed dramatically. In 1837, Jacquard's loom inspired Charles Babbage to attempt to build

2277-418: Is assigned to a class. An assigned function is then referred to as a method , member function , or operation . Object-oriented programming is executing operations on objects . Object-oriented languages support a syntax to model subset/superset relationships. In set theory , an element of a subset inherits all the attributes contained in the superset. For example, a student is a person. Therefore,

2376-453: Is called source code . Source code needs another computer program to execute because computers can only execute their native machine instructions . Therefore, source code may be translated to machine instructions using a compiler written for the language. ( Assembly language programs are translated using an assembler .) The resulting file is called an executable . Alternatively, source code may execute within an interpreter written for

2475-492: Is just to tell you that I shall be thinking of Chris and of you tomorrow. I am sure that he is as happy now as he was when he was here. Your affectionate Alan. Some have speculated that Morcom's death was the cause of Turing's atheism and materialism . Apparently, at this point in his life he still believed in such concepts as a spirit, independent of the body and surviving death. In a later letter, also written to Morcom's mother, Turing wrote: Personally, I believe that spirit

2574-442: Is known as the x86 series . The x86 assembly language is a family of backward-compatible machine instructions . Machine instructions created in earlier microprocessors were retained throughout microprocessor upgrades. This enabled consumers to purchase new computers without having to purchase new application software . The major categories of instructions are: VLSI circuits enabled the programming environment to advance from

2673-453: Is possible that he managed to deduce Einstein's questioning of Newton's laws of motion from a text in which this was never made explicit. At Sherborne, Turing formed a significant friendship with fellow pupil Christopher Collan Morcom (13 July 1911 – 13 February 1930), who has been described as Turing's first love. Their relationship provided inspiration in Turing's future endeavours, but it

2772-403: Is really eternally connected with matter but certainly not by the same kind of body ... as regards the actual connection between spirit and body I consider that the body can hold on to a 'spirit', whilst the body is alive and awake the two are firmly connected. When the body is asleep I cannot guess what happens but when the body dies, the 'mechanism' of the body, holding the spirit is gone and

2871-524: Is recognised more widely, with statues and many things named after him , including an annual award for computing innovation. His portrait appears on the Bank of England £50 note , first released on 23 June 2021 to coincide with his birthday. The audience vote in a 2019 BBC series named Turing the greatest person of the 20th century. Turing was born in Maida Vale , London, while his father, Julius Mathison Turing,

2970-427: Is then thinly sliced to form a wafer substrate . The planar process of photolithography then integrates unipolar transistors, capacitors , diodes , and resistors onto the wafer to build a matrix of metal–oxide–semiconductor (MOS) transistors. The MOS transistor is the primary component in integrated circuit chips . Originally, integrated circuit chips had their function set during manufacturing. During

3069-422: Is to stay at public school, he must aim at becoming educated . If he is to be solely a Scientific Specialist , he is wasting his time at a public school". Despite this, Turing continued to show remarkable ability in the studies he loved, solving advanced problems in 1927 without having studied even elementary calculus . In 1928, aged 16, Turing encountered Albert Einstein 's work; not only did he grasp it, but it

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3168-570: The new statement. A module's other file is the source file . Here is a C++ source file for the GRADE class in a simple school application: Here is a C++ header file for the PERSON class in a simple school application: Alan Turing Alan Mathison Turing ( / ˈ tj ʊər ɪ ŋ / ; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist , logician , cryptanalyst , philosopher and theoretical biologist . He

3267-502: The Analytical Engine . The names of the components of the calculating device were borrowed from the textile industry. In the textile industry, yarn was brought from the store to be milled. The device had a store which consisted of memory to hold 1,000 numbers of 50 decimal digits each. Numbers from the store were transferred to the mill for processing. The engine was programmed using two sets of perforated cards. One set directed

3366-600: The Busicom calculator. Five months after its release, Intel released the Intel 8008 , an 8-bit microprocessor. Bill Pentz led a team at Sacramento State to build the first microcomputer using the Intel 8008: the Sac State 8008 (1972). Its purpose was to store patient medical records. The computer supported a disk operating system to run a Memorex , 3- megabyte , hard disk drive . It had

3465-467: The Department of Mathematics at Princeton; his dissertation, Systems of Logic Based on Ordinals , introduced the concept of ordinal logic and the notion of relative computing , in which Turing machines are augmented with so-called oracles , allowing the study of problems that cannot be solved by Turing machines. John von Neumann wanted to hire him as his postdoctoral assistant , but he went back to

3564-824: The Enigma machine . He played a crucial role in cracking intercepted messages that enabled the Allies to defeat the Axis powers in many engagements, including the Battle of the Atlantic . After the war, Turing worked at the National Physical Laboratory , where he designed the Automatic Computing Engine , one of the first designs for a stored-program computer. In 1948, Turing joined Max Newman 's Computing Machine Laboratory at

3663-525: The Mathematical Tripos , with extra courses at the end of the third year, as Part III only emerged as a separate degree in 1934) from February 1931 to November 1934 at King's College, Cambridge , where he was awarded first-class honours in mathematics. His dissertation, On the Gaussian error function , written during his senior year and delivered in November 1934 (with a deadline date of 6 December) proved

3762-484: The Proceedings of the London Mathematical Society journal in two parts, the first on 30 November and the second on 23 December. In this paper, Turing reformulated Kurt Gödel 's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines . The Entscheidungsproblem (decision problem)

3861-521: The Turing baronets . Turing's father's civil service commission was still active during Turing's childhood years, and his parents travelled between Hastings in the United Kingdom and India, leaving their two sons to stay with a retired Army couple. At Hastings, Turing stayed at Baston Lodge , Upper Maze Hill, St Leonards-on-Sea , now marked with a blue plaque. The plaque was unveiled on 23 June 2012,

3960-599: The Victoria University of Manchester , where he helped develop the Manchester computers and became interested in mathematical biology . Turing wrote on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction , first observed in the 1960s. Despite these accomplishments, he was never fully recognised during his lifetime because much of his work

4059-455: The 1960s, controlling the electrical flow migrated to programming a matrix of read-only memory (ROM). The matrix resembled a two-dimensional array of fuses. The process to embed instructions onto the matrix was to burn out the unneeded connections. There were so many connections, firmware programmers wrote a computer program on another chip to oversee the burning. The technology became known as Programmable ROM . In 1971, Intel installed

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4158-578: The ENIAC project. On June 30, 1945, von Neumann published the First Draft of a Report on the EDVAC , which equated the structures of the computer with the structures of the human brain. The design became known as the von Neumann architecture . The architecture was simultaneously deployed in the constructions of the EDVAC and EDSAC computers in 1949. The IBM System/360 (1964) was a family of computers, each having

4257-600: The ENIAC took up to two months. Three function tables were on wheels and needed to be rolled to fixed function panels. Function tables were connected to function panels by plugging heavy black cables into plugboards . Each function table had 728 rotating knobs. Programming the ENIAC also involved setting some of the 3,000 switches. Debugging a program took a week. It ran from 1947 until 1955 at Aberdeen Proving Ground , calculating hydrogen bomb parameters, predicting weather patterns, and producing firing tables to aim artillery guns. Instead of plugging in cords and turning switches,

4356-655: The Enigma cipher machine used by Nazi Germany , together with Dilly Knox , a senior GC&CS codebreaker. Soon after the July 1939 meeting near Warsaw at which the Polish Cipher Bureau gave the British and French details of the wiring of Enigma machine's rotors and their method of decrypting Enigma machine 's messages, Turing and Knox developed a broader solution. The Polish method relied on an insecure indicator procedure that

4455-575: The Germans were likely to change, which they in fact did in May 1940. Turing's approach was more general, using crib-based decryption for which he produced the functional specification of the bombe (an improvement on the Polish Bomba ). On 4 September 1939, the day after the UK declared war on Germany, Turing reported to Bletchley Park, the wartime station of GC&CS. Like all others who came to Bletchley, he

4554-637: The ICS brought the family to British India, where his grandfather had been a general in the Bengal Army . However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to Maida Vale , London, where Alan Turing was born on 23 June 1912, as recorded by a blue plaque on the outside of the house of his birth, later the Colonnade Hotel . Turing had an elder brother, John Ferrier Turing, father of Sir John Dermot Turing , 12th Baronet of

4653-568: The Nova PBS documentary Decoding Nazi Secrets . While working at Bletchley, Turing, who was a talented long-distance runner , occasionally ran the 40 miles (64 km) to London when he was needed for meetings, and he was capable of world-class marathon standards. Turing tried out for the 1948 British Olympic team , but he was hampered by an injury. His tryout time for the marathon was only 11 minutes slower than British silver medallist Thomas Richards ' Olympic race time of 2 hours 35 minutes. He

4752-446: The Second World War, Turing was a leading participant in the breaking of German ciphers at Bletchley Park . The historian and wartime codebreaker Asa Briggs has said, "You needed exceptional talent, you needed genius at Bletchley and Turing's was that genius." From September 1938, Turing worked part-time with the Government Code and Cypher School (GC&CS), the British codebreaking organisation. He concentrated on cryptanalysis of

4851-493: The United Kingdom. When Turing returned to Cambridge, he attended lectures given in 1939 by Ludwig Wittgenstein about the foundations of mathematics . The lectures have been reconstructed verbatim, including interjections from Turing and other students, from students' notes. Turing and Wittgenstein argued and disagreed, with Turing defending formalism and Wittgenstein propounding his view that mathematics does not discover any absolute truths, but rather invents them. During

4950-414: The bombe performed a chain of logical deductions based on the crib, implemented electromechanically . The bombe detected when a contradiction had occurred and ruled out that setting, moving on to the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. A contradiction would occur when an enciphered letter would be turned back into

5049-497: The bombes; developing a procedure dubbed Turingery for working out the cam settings of the wheels of the Lorenz SZ 40/42 ( Tunny ) cipher machine and, towards the end of the war, the development of a portable secure voice scrambler at Hanslope Park that was codenamed Delilah . By using statistical techniques to optimise the trial of different possibilities in the code breaking process, Turing made an innovative contribution to

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5148-505: The centenary of Turing's birth. Very early in life, Turing's parents purchased a house in Guildford in 1927, and Turing lived there during school holidays. The location is also marked with a blue plaque. Turing's parents enrolled him at St Michael's, a primary school at 20 Charles Road, St Leonards-on-Sea , from the age of six to nine. The headmistress recognised his talent, noting that she "...had clever boys and hardworking boys, but Alan

5247-516: The chain by hand. Another of his eccentricities is that he chained his mug to the radiator pipes to prevent it being stolen. Peter Hilton recounted his experience working with Turing in Hut 8 in his "Reminiscences of Bletchley Park" from A Century of Mathematics in America: It is a rare experience to meet an authentic genius. Those of us privileged to inhabit the world of scholarship are familiar with

5346-464: The chief of the secret service reported that every possible measure was being taken. The cryptographers at Bletchley Park did not know of the Prime Minister's response, but as Milner-Barry recalled, "All that we did notice was that almost from that day the rough ways began miraculously to be made smooth." More than two hundred bombes were in operation by the end of the war. Turing decided to tackle

5445-399: The committee went so far as to say that if Turing's work had been published before Lindeberg's, it would have been "an important event in the mathematical literature of that year". Between the springs of 1935 and 1936, at the same time as Alonzo Church , Turing worked on the decidability of problems, starting from Gödel's incompleteness theorems . In mid-April 1936, Turing sent Max Newman

5544-476: The computer program onto the chip and named it the Intel 4004 microprocessor . The terms microprocessor and central processing unit (CPU) are now used interchangeably. However, CPUs predate microprocessors. For example, the IBM System/360 (1964) had a CPU made from circuit boards containing discrete components on ceramic substrates . The Intel 4004 (1971) was a 4- bit microprocessor designed to run

5643-461: The computer. They follow a set of rules called a syntax . Programming languages get their basis from formal languages . The purpose of defining a solution in terms of its formal language is to generate an algorithm to solve the underlining problem. An algorithm is a sequence of simple instructions that solve a problem. The evolution of programming languages began when the EDSAC (1949) used

5742-434: The descendants include C , C++ and Java . BASIC (1964) stands for "Beginner's All-Purpose Symbolic Instruction Code". It was developed at Dartmouth College for all of their students to learn. If a student did not go on to a more powerful language, the student would still remember Basic. A Basic interpreter was installed in the microcomputers manufactured in the late 1970s. As the microcomputer industry grew, so did

5841-643: The first stored computer program in its von Neumann architecture . Programming the EDSAC was in the first generation of programming language . Imperative languages specify a sequential algorithm using declarations , expressions , and statements : FORTRAN (1958) was unveiled as "The IBM Mathematical FORmula TRANslating system". It was designed for scientific calculations, without string handling facilities. Along with declarations , expressions , and statements , it supported: It succeeded because: However, non-IBM vendors also wrote Fortran compilers, but with

5940-464: The first draft typescript of his investigations. That same month, Church published his An Unsolvable Problem of Elementary Number Theory , with similar conclusions to Turing's then-yet unpublished work. Finally, on 28 May of that year, he finished and delivered his 36-page paper for publication called " On Computable Numbers, with an Application to the Entscheidungsproblem ". It was published in

6039-478: The first named. They emphasised how small their need was compared with the vast expenditure of men and money by the forces and compared with the level of assistance they could offer to the forces. As Andrew Hodges , biographer of Turing, later wrote, "This letter had an electric effect." Churchill wrote a memo to General Ismay , which read: "ACTION THIS DAY. Make sure they have all they want on extreme priority and report to me that this has been done." On 18 November,

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6138-539: The halt state. All present-day computers are Turing complete . The Electronic Numerical Integrator And Computer (ENIAC) was built between July 1943 and Fall 1945. It was a Turing complete , general-purpose computer that used 17,468 vacuum tubes to create the circuits . At its core, it was a series of Pascalines wired together. Its 40 units weighed 30 tons, occupied 1,800 square feet (167 m ), and consumed $ 650 per hour ( in 1940s currency ) in electricity when idle. It had 20 base-10 accumulators . Programming

6237-460: The idea that such a machine could perform the tasks of any other computation machine (as indeed could Church's lambda calculus). According to the Church–Turing thesis , Turing machines and the lambda calculus are capable of computing anything that is computable. John von Neumann acknowledged that the central concept of the modern computer was due to Turing's paper. To this day, Turing machines are

6336-414: The intellectual stimulation furnished by talented colleagues. We can admire the ideas they share with us and are usually able to understand their source; we may even often believe that we ourselves could have created such concepts and originated such thoughts. However, the experience of sharing the intellectual life of a genius is entirely different; one realizes that one is in the presence of an intelligence,

6435-475: The language BCPL was replaced with B , and AT&T Bell Labs called the next version "C". Its purpose was to write the UNIX operating system . C is a relatively small language, making it easy to write compilers. Its growth mirrored the hardware growth in the 1980s. Its growth also was because it has the facilities of assembly language , but uses a high-level syntax . It added advanced features like: C allows

6534-400: The language. Basic pioneered the interactive session . It offered operating system commands within its environment: However, the Basic syntax was too simple for large programs. Recent dialects added structure and object-oriented extensions. Microsoft's Visual Basic is still widely used and produces a graphical user interface . C programming language (1973) got its name because

6633-410: The language. If the executable is requested for execution, then the operating system loads it into memory and starts a process . The central processing unit will soon switch to this process so it can fetch, decode, and then execute each machine instruction. If the source code is requested for execution, then the operating system loads the corresponding interpreter into memory and starts

6732-432: The more likely settings so that they can be tried as quickly as possible". ... Richard said that GCHQ had now "squeezed the juice" out of the two papers and was "happy for them to be released into the public domain". Turing had a reputation for eccentricity at Bletchley Park. He was known to his colleagues as "Prof" and his treatise on Enigma was known as the "Prof's Book". According to historian Ronald Lewin , Jack Good ,

6831-466: The naval Enigma, "though I was not sure that it would work in practice, and was not, in fact, sure until some days had actually broken". For this, he invented a measure of weight of evidence that he called the ban . Banburismus could rule out certain sequences of the Enigma rotors, substantially reducing the time needed to test settings on the bombes. Later this sequential process of accumulating sufficient weight of evidence using decibans (one tenth of

6930-478: The operation and the other set inputted the variables. However, the thousands of cogged wheels and gears never fully worked together. Ada Lovelace worked for Charles Babbage to create a description of the Analytical Engine (1843). The description contained Note G which completely detailed a method for calculating Bernoulli numbers using the Analytical Engine. This note is recognized by some historians as

7029-556: The particularly difficult problem of cracking the German naval use of Enigma "because no one else was doing anything about it and I could have it to myself". In December 1939, Turing solved the essential part of the naval indicator system, which was more complex than the indicator systems used by the other services. That same night, he also conceived of the idea of Banburismus , a sequential statistical technique (what Abraham Wald later called sequential analysis ) to assist in breaking

7128-420: The primary tools, and the major automated one, used to attack Enigma-enciphered messages. The bombe searched for possible correct settings used for an Enigma message (i.e., rotor order, rotor settings and plugboard settings) using a suitable crib : a fragment of probable plaintext . For each possible setting of the rotors (which had on the order of 10 states, or 10 states for the four-rotor U-boat variant),

7227-443: The programmer to control which region of memory data is to be stored. Global variables and static variables require the fewest clock cycles to store. The stack is automatically used for the standard variable declarations . Heap memory is returned to a pointer variable from the malloc() function. In the 1970s, software engineers needed language support to break large projects down into modules . One obvious feature

7326-501: The project contributed to the development of the Intel 8080 (1974) instruction set . In 1978, the modern software development environment began when Intel upgraded the Intel 8080 to the Intel 8086 . Intel simplified the Intel 8086 to manufacture the cheaper Intel 8088 . IBM embraced the Intel 8088 when they entered the personal computer market (1981). As consumer demand for personal computers increased, so did Intel's microprocessor development. The succession of development

7425-446: The same instruction set architecture . The Model 20 was the smallest and least expensive. Customers could upgrade and retain the same application software . The Model 195 was the most premium. Each System/360 model featured multiprogramming —having multiple processes in memory at once. When one process was waiting for input/output , another could compute. IBM planned for each model to be programmed using PL/1 . A committee

7524-468: The same plaintext letter, which was impossible with the Enigma. The first bombe was installed on 18 March 1940. By late 1941, Turing and his fellow cryptanalysts Gordon Welchman , Hugh Alexander and Stuart Milner-Barry were frustrated. Building on the work of the Poles , they had set up a good working system for decrypting Enigma signals, but their limited staff and bombes meant they could not translate all

7623-438: The set of students is a subset of the set of persons. As a result, students inherit all the attributes common to all persons. Additionally, students have unique attributes that other people do not have. Object-oriented languages model subset/superset relationships using inheritance . Object-oriented programming became the dominant language paradigm by the late 1990s. C++ (1985) was originally called "C with Classes". It

7722-407: The signals. In the summer, they had considerable success, and shipping losses had fallen to under 100,000 tons a month; however, they badly needed more resources to keep abreast of German adjustments. They had tried to get more people and fund more bombes through the proper channels, but had failed. On 28 October they wrote directly to Winston Churchill explaining their difficulties, with Turing as

7821-463: The spirit finds a new body sooner or later, perhaps immediately. After graduating from Sherborne, Turing applied for several Cambridge colleges scholarships, including Trinity and King's , eventually earning an £80 per annum scholarship (equivalent to about £4,300 as of 2023) to study at the latter. There, Turing studied the undergraduate course in Schedule B (that is, a three-year Parts I and II, of

7920-485: The subject. He wrote two papers discussing mathematical approaches, titled The Applications of Probability to Cryptography and Paper on Statistics of Repetitions , which were of such value to GC&CS and its successor GCHQ that they were not released to the UK National Archives until April 2012, shortly before the centenary of his birth. A GCHQ mathematician, "who identified himself only as Richard," said at

8019-473: The time that the fact that the contents had been restricted under the Official Secrets Act for some 70 years demonstrated their importance, and their relevance to post-war cryptanalysis: [He] said the fact that the contents had been restricted "shows what a tremendous importance it has in the foundations of our subject". ... The papers detailed using "mathematical analysis to try and determine which are

8118-470: The war. However, official war historian Harry Hinsley estimated that this work shortened the war in Europe by more than two years and saved over 14 million lives. At the end of the war, a memo was sent to all those who had worked at Bletchley Park, reminding them that the code of silence dictated by the Official Secrets Act did not end with the war but would continue indefinitely. Thus, even though Turing

8217-499: The world's first computer program . In 1936, Alan Turing introduced the Universal Turing machine , a theoretical device that can model every computation. It is a finite-state machine that has an infinitely long read/write tape. The machine can move the tape back and forth, changing its contents as it performs an algorithm . The machine starts in the initial state, goes through a sequence of steps, and halts when it encounters

8316-679: Was Ethel Sara Turing ( née  Stoney ), daughter of Edward Waller Stoney, chief engineer of the Madras Railways . The Stoneys were a Protestant Anglo-Irish gentry family from both County Tipperary and County Longford , while Ethel herself had spent much of her childhood in County Clare . Julius and Ethel married on 1 October 1907 at the Church of Ireland St. Bartholomew's Church on Clyde Road in Ballsbridge , Dublin . Julius's work with

8415-417: Was Walton Athletic Club's best runner, a fact discovered when he passed the group while running alone. When asked why he ran so hard in training he replied: I have such a stressful job that the only way I can get it out of my mind is by running hard; it's the only way I can get some release. Due to the problems of counterfactual history , it is hard to estimate the precise effect Ultra intelligence had on

8514-643: Was appointed an Officer of the Order of the British Empire (OBE) in 1946 by King George VI for his wartime services, his work remained secret for many years. Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine called the bombe , which could break Enigma more effectively than the Polish bomba kryptologiczna , from which its name was derived. The bombe, with an enhancement suggested by mathematician Gordon Welchman , became one of

8613-464: Was covered by the Official Secrets Act . In 1952, Turing was prosecuted for homosexual acts . He accepted hormone treatment, a procedure commonly referred to as chemical castration , as an alternative to prison. Turing died on 7 June 1954, aged 41, from cyanide poisoning . An inquest determined his death as suicide , but the evidence is also consistent with accidental poisoning. Following

8712-725: Was cut short by Morcom's death, in February 1930, from complications of bovine tuberculosis , contracted after drinking infected cow's milk some years previously. The event caused Turing great sorrow. He coped with his grief by working that much harder on the topics of science and mathematics that he had shared with Morcom. In a letter to Morcom's mother, Frances Isobel Morcom (née Swan), Turing wrote: I am sure I could not have found anywhere another companion so brilliant and yet so charming and unconceited. I regarded my interest in my work, and in such things as astronomy (to which he introduced me) as something to be shared with him and I think he felt

8811-427: Was designed to expand C's capabilities by adding the object-oriented facilities of the language Simula . An object-oriented module is composed of two files. The definitions file is called the header file . Here is a C++ header file for the GRADE class in a simple school application: A constructor operation is a function with the same name as the class name. It is executed when the calling operation executes

8910-422: Was elected a Fellow of King's College on the strength of his dissertation where he served as a lecturer . However, and, unknown to Turing, this version of the theorem he proved in his paper, had already been proven, in 1922, by Jarl Waldemar Lindeberg . Despite this, the committee found Turing's methods original and so regarded the work worthy of consideration for the fellowship. Abram Besicovitch 's report for

9009-437: Was formed that included COBOL , Fortran and ALGOL programmers. The purpose was to develop a language that was comprehensive, easy to use, extendible, and would replace Cobol and Fortran. The result was a large and complex language that took a long time to compile . Computers manufactured until the 1970s had front-panel switches for manual programming. The computer program was written on paper for reference. An instruction

9108-500: Was highly influential in the development of theoretical computer science , providing a formalisation of the concepts of algorithm and computation with the Turing machine , which can be considered a model of a general-purpose computer . Turing is widely considered to be the father of theoretical computer science. Born in London, Turing was raised in southern England . He graduated from King's College, Cambridge , and in 1938, earned

9207-775: Was on leave from his position with the Indian Civil Service (ICS) of the British Raj government at Chatrapur , then in the Madras Presidency and presently in Odisha state, in India . Turing's father was the son of a clergyman, the Rev. John Robert Turing, from a Scottish family of merchants that had been based in the Netherlands and included a baronet . Turing's mother, Julius's wife,

9306-446: Was originally posed by German mathematician David Hilbert in 1928. Turing proved that his "universal computing machine" would be capable of performing any conceivable mathematical computation if it were representable as an algorithm . He went on to prove that there was no solution to the decision problem by first showing that the halting problem for Turing machines is undecidable : it is not possible to decide algorithmically whether

9405-408: Was represented by a configuration of on/off settings. After setting the configuration, an execute button was pressed. This process was then repeated. Computer programs also were automatically inputted via paper tape , punched cards or magnetic-tape . After the medium was loaded, the starting address was set via switches, and the execute button was pressed. A major milestone in software development

9504-548: Was required to sign the Official Secrets Act , in which he agreed not to disclose anything about his work at Bletchley, with severe legal penalties for violating the Act. Specifying the bombe was the first of five major cryptanalytical advances that Turing made during the war. The others were: deducing the indicator procedure used by the German navy; developing a statistical procedure dubbed Banburismus for making much more efficient use of

9603-440: Was so determined to attend that he rode his bicycle unaccompanied 60 miles (97 km) from Southampton to Sherborne, stopping overnight at an inn. Turing's natural inclination towards mathematics and science did not earn him respect from some of the teachers at Sherborne, whose definition of education placed more emphasis on the classics . His headmaster wrote to his parents: "I hope he will not fall between two stools. If he

9702-531: Was the invention of the Very Large Scale Integration (VLSI) circuit (1964). Following World War II , tube-based technology was replaced with point-contact transistors (1947) and bipolar junction transistors (late 1950s) mounted on a circuit board . During the 1960s , the aerospace industry replaced the circuit board with an integrated circuit chip . Robert Noyce , co-founder of Fairchild Semiconductor (1957) and Intel (1968), achieved

9801-405: Was to decompose large projects physically into separate files . A less obvious feature was to decompose large projects logically into abstract data types . At the time, languages supported concrete (scalar) datatypes like integer numbers, floating-point numbers, and strings of characters . Abstract datatypes are structures of concrete datatypes, with a new name assigned. For example,

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