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he history of science began long before the modern discipline of that emerged in the 20th century, and hinted at in the centuries prior.[dubious – discuss][citation needed] The progression, from mechanical inventions and mathematical theories towards the modern concepts and machines, formed a major academic field and the basis of a massive worldwide industry.[1]

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[show] Early history[edit]

The earliest known as tool for use in computation was the abacus, developed in period 2700–2300 BCE in Sumer[citation needed]. The Sumerians' abacus consisted of a table of successive columns which delimited the successive orders of magnitude of their sexagesimal number system.[2] Its original style of usage was by lines drawn in sand with pebbles[citation needed]. Abaci of a more modern design are still used as calculation tools today.[3]

The Antikythera mechanism is believed to be the earliest known mechanical analog computer.[4] It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to c. 100 BCE. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanical astronomical clocks appeared inEurope.[5]

Mechanical analog computing devices appeared a thousand years later in the medieval Islamic world. Examples of [6] devices from this period include the equatorium by Arzachel, the mechanical geared astrolabe by Abū Rayhān al- [7] [8] Bīrūnī, and the torquetum by Jabir ibn Aflah. Muslim engineers built a number of automata, including some musical automata that could be 'programmed' to play different musical patterns. These devices were developed by [9] [10] the Banū Mūsā brothers and Al-Jazari Muslim mathematicians also made important advances in cryptography, such as the development of and by Alkindus.[11]

When John Napier discovered for computational purposes in the early 17th century,[citation needed] there followed a period of considerable progress by inventors and scientists in making calculating tools. In 1623 Wilhelm Schickard designed a calculating machine, but abandoned the project, when the prototype he had started building was destroyed by a fire in 1624[citation needed]. Around 1640, Blaise Pascal, a leading French mathematician, constructed the first mechanical adding device[12] based on a design described by Greek mathematician Hero of Alexandria.[13]Then in 1672 Gottfried Wilhelm Leibnitz invented the Stepped Reckoner which he completed in 1694.[14]

In 1837 first described his Analytical Engine which is accepted as the first design for a modern computer. The analytical engine had expandable memory, an arithmetic unit, and logic processing capabilities able to interpret a programming language with loops and conditional branching. Although never built, the design has been studied extensively and is understood to beTuring complete. The analytical engine would have had a memory capacity of less than 1 kilobyte of memory and a clock speed of less than 10 Hertz[citation needed].

Considerable advancement in mathematics and electronics theory was required before the first modern could be designed[citation needed]. Binary logic[edit] In 1703, Gottfried Wilhelm Leibnitz developed logic in a formal, mathematical sense with his writings on the binary numeral system. In his system, the ones and zeros also represent true andfalse values or on and off states. But it took more than a century before George Boole published his Boolean algebra in 1854 with a complete system that allowed computational processes to be mathematically modeled[citation needed].

By this time, the first mechanical devices driven by a binary pattern had been invented. The industrial revolution had driven forward the mechanization of many tasks, and this included weaving.Punched cards controlled Joseph Marie Jacquard's loom in 1801, where a hole punched in the card indicated a binary one and an unpunched spot indicated a binary zero. Jacquard's loom was far from being a computer, but it did illustrate that machines could be driven by binary systems[citation needed]. Birth of computer[edit] Before the 1920s, computers (sometimes computors) were human clerks that performed computations. They were usually under the lead of a physicist. Many thousands of computers were employed in commerce, government, and research establishments. Most of these computers were women, and they were known to have a degree in calculus. Some performed astronomical calculations for calendars[citation needed].

After the 1920s, the expression computing machine referred to any machine that performed the work of a human computer, especially those in accordance with effective methods of the Church-Turing thesis. The thesis states that a mathematical method is effective if it could be set out as a list of instructions able to be followed by a human clerk with paper and pencil, for as long as necessary, and without ingenuity or insight[citation needed].

Machines that computed with continuous values became known as the analog kind. They used machinery that represented continuous numeric quantities, like the angle of a shaft rotation or difference in electrical potential[citation needed].

Digital machinery, in contrast to analog, were able to render a state of a numeric value and store each individual digit. Digital machinery used difference engines or relays before the invention of faster memory devices[citation needed].

The phrase computing machine gradually gave away, after the late 1940s, to just computer as the onset of electronic digital machinery became common. These computers were able to perform the calculations that were performed by the previous human clerks[citation needed].

Since the values stored by digital machines were not bound to physical properties like analog devices, a logical computer, based on digital equipment, was able to do anything that could be described "purely mechanical." The theoretical , created by , is a hypothetical device theorized in order to study the properties of such hardware[citation needed].

See also: Philosophy of physics, Philosophy of biology, Philosophy of mathematics, Philosophy of language, and Philosophy of mind Emergence of a discipline[edit]

Charles Babbage and [edit] Charles Babbage is often regarded as one of the first pioneers of computing. Beginning in the 1810s, Babbage had a vision of mechanically computing numbers and tables. Putting this into reality, Babbage designed a to compute numbers up to 8 decimal points long. Continuing with the success of this idea, Babbage worked to develop a machine that could compute numbers with up to 20 decimal places. By the 1830s, Babbage had devised a plan to develop a machine that could use punched cards to perform arithmetical operations. The machine would store numbers in memory units, and there would be a form of sequential control. This means that one operation would be carried out before another in such a way that the machine would produce an answer and not fail. This machine was [15] to be known as the ―Analytical Engine‖, which was the first true representation of what is the modern computer.

Ada Lovelace (Augusta Ada Byron) is credited as the pioneer of computer programming and is regarded as a mathematical genius, a result of the mathematically heavy tutoring regimen her mother assigned to her as a young girl. Lovelace began working with Charles Babbage as an assistant while Babbage was working on his ―Analytical Engine‖, the first mechanical computer. During her work with Babbage, Ada Lovelace became the designer of the first computer , which had the ability to compute Bernoulli‘s numbers. Moreover, Lovelace‘s work with Babbage resulted in her prediction of future computers to not only perform mathematical calculations, but also manipulate symbols, mathematical or not. While she was never able to see the results of her work, as the ―Analytical Engine‖ was not created in her lifetime, her efforts in later years, beginning in the 1940s, did not go unnoticed.[16] Alan Turing and the Turing Machine[edit] The mathematical foundations of modern computer science began to be laid by Kurt Gödel with his incompleteness theorem (1931). In this theorem, he showed that there were limits to what could be proved and disproved within a formal system. This led to work by Gödel and others to define and describe these formal systems, including concepts such as mu-recursive functions andlambda-definable functions[citation needed].

1936 was a key year for computer science. Alan Turing and Alonzo Church independently, and also together, introduced the formalization of an algorithm, with limits on what can be computed, and a "purely mechanical" model for computing[citation needed].

These topics are covered by what is now called the Church–Turing thesis, a hypothesis about the nature of mechanical calculation devices, such as electronic computers. The thesis claims that any calculation that is possible can be performed by an algorithm running on a computer, provided that sufficient time and storage space are available[citation needed].

In 1937, Alan Turing introduced his idea of what are now referred to as Turing Machines, and, anticipating the modern stored program computer, described what became known as the Universal Turing machine. These Turing machines were designed to formally determine, mathematically, what can be computed, taking into account limitations on computing ability. If a Turing machine can complete the task, it is considered Turing computable.[17]

Turing machines are not physical objects, but mathematical ones. They show if and how any given algorithm can be computed. Turing machines are state machines, where a state represents a position in a graph. State machines use various states, or graph positions, to determine the outcome of the algorithm. To accomplish this, a theoretical one- dimensional tape is said to be divided into an infinite number of cells. Each cell contains a binary digit, 1 or 0. As the read/write head of the machine scans in the subsequent value in the cell, it uses this value to determine what state to transition to next. To accomplish this, the machine follows an input of rules, usually in the form of tables, that contain logic similar to: if the machine is in state A and a 0 is read in, the machine is going to go to the next state, say, state B. The rules that the machines must follow are considered the program. These Turing machines helped define the logic behind modern computer science. Memory in modern computers is represented by the infinite tape, and the bus of the machine is represented by the read/write head.[17]

Turing focused heavily on designing a machine that could determine what can be computed. Turing concluded that as long as a Turing machine exists that could compute a precise approximation of the number, that value was computable. This does include constants such as pi. Furthermore, functions can be computable when determining TRUE or FALSE for any given parameters. One example of this would be a function ―IsEven‖. If this function were passed a number, the computation would produce TRUE if the number were even and FALSE if the number were odd. Using these specifications, Turing machines can determine if a function is computable and terminate if said function is computable. Furthermore, Turing machines can interpret logic operators, such as "AND, OR, XOR, NOT, and IF-THEN-ELSE"[17] to determine if a function is computable.

Turing is so important to computer science that his name is also featured on the Turing Award and the Turing test. He contributed greatly to British code-breaking successes in the Second World War, and continued to design computers and through the 1940s until his untimely death in 1954[citation needed].

At a symposium on large-scale digital machinery in Cambridge, Turing said, "We are trying to build a machine to do all kinds of different things simply by programming rather than by the addition of extra apparatus"[citation needed].

In 1941, Konrad Zuse developed the world's first functional program-controlled Turing-complete computer, the Z3. Zuse was also noted for the S2 computing machine, considered the first process-controlled computer. He founded one of the earliest computer businesses in 1941, producing the Z4, which became the world's first commercial computer. In 1946, he designed the first high-levelprogramming language, Plankalkül.[18] In 1969, Zuse suggested the concept of a computation-based universe in his book Rechnender Raum (Calculating Space)[citation needed]. In 1948, the first practical computer that could run stored programs, based on the Turing machine model, had been built - the Manchester Baby[citation needed].

In 1950, Britain's National Physical Laboratory completed Pilot ACE, a small scale programmable computer, based on Turing's philosophy[citation needed]. Shannon and information theory[edit] Up to and during the 1930s, electrical engineers were able to build electronic circuits to solve mathematical and logic problems, but most did so in an ad hoc manner, lacking any theoretical rigor. This changed with Claude Elwood Shannon's publication of his 1937 master's thesis, A Symbolic Analysis of Relay and Switching Circuits. While taking an undergraduate philosophy class, Shannon had been exposed to Boole's work, and recognized that it could be used to arrange electromechanical relays (then used in telephone routing switches) to solve logic problems. This concept, of utilizing the properties of electrical switches to do logic, is the basic concept that underlies all electronic digital computers, and his thesis became the foundation of practical digital circuit design when it became widely known among the electrical engineering community during and after World War II[citation needed].

Shannon went on to found the field of information theory with his 1948 paper titled A Mathematical Theory of Communication, which applied probability theory to the problem of how to best encode the information a sender wants to transmit. This work is one of the theoretical foundations for many areas of study, including data compression and cryptography[citation needed]. Wiener and Cybernetics[edit] From experiments with anti-aircraft systems that interpreted radar images to detect enemy planes, coined the term cybernetics from the Greek word for "steersman." He published "Cybernetics" in 1948, which influenced artificial intelligence. Wiener also compared computation, computing machinery, memory devices, and other cognitive similarities with his analysis of brain waves[citation needed].

The first actual computer bug was a moth. It was stuck in between the relays on the Harvard Mark II.[1] While the invention of the term 'bug' is often but erroneously attributed to , a future rear admiral in the U.S. Navy, who supposedly logged the "bug" on September 9, 1945, most other accounts conflict at least with these details. According to these accounts, the actual date was September 9, 1947 when operators filed this 'incident' — along with the insect and the notation "First actual case of bug being found" (see software bug for details)[citation needed]. and the [edit] In 1946, a model for computer architecture was introduced and became known as von Neumann Architecture. Since 1950, the von Neumann model provided uniformity in subsequent computer designs. The von Neumann Architecture was considered innovative as it introduced an idea of allowing machine instructions and data to share memory space. The von Neumann model is composed of 3 major parts, the arithmetic logic unit (ALU), the memory, and the instruction processing unit (IPU). In von Neumann machine design, the IPU passes addresses to memory, and memory, in turn, is routed either back to the IPU if an instruction is being fetched or to the ALU if data is being fetched.[19]

Von Neumann‘s machine design uses a RISC (Reduced instruction set computing) architecture, which means the instruction set uses a total of 21 instructions to perform all tasks. (This is in contrast to CISC, complex instruction set computing, instruction sets which have more instructions from which to choose.) Addresses, operations and data types comprise this instruction set. With von Neumann architecture, main memory along with the accumulator (the register that holds the result of logical operations)[20] are the two memories that are addressed. Operations can be carried out as simple arithmetic (these are performed by the ALU and include addition, subtraction, multiplication and division), conditional branches (these are more commonly seen now as ―if‖ statements or ―while‖ loops. The branches serve as ‗go to‘ statements), and logical moves between the different components of the machine, i.e., a move from the accumulator to memory or vice versa. Von Neumann architecture accepts fractions and instructions as data types. Finally, as the von Neumann architecture is a simple one, its register management is also simple. The architecture uses a set of seven registers to manipulate and interpret fetched data and instructions. These registers include the "IR (instruction register), IBR (instruction buffer register), MQ (multiplier quotient register), MAR (memory address register), and MDR (memory data register)."[19] The architecture also uses a program counter (PC) to keep track of where in the program the machine is.[19] See also[edit]

 History of computing  History of computing hardware  History of software  Timeline of  List of prominent pioneers in computer science  List of computer term etymologies, the origins of computer science words  Computer Museum Notes[edit]

1. Jump up^ History of Computer Science

2. Jump up^ Ifrah 2001:11

3. Jump up^ Bellos, Alex. "Abacus adds up to number joy in Japan". Retrieved 2013-06-25.

4. Jump up^ The Antikythera Mechanism Research Project, The Antikythera Mechanism Research Project. Retrieved

2007-07-01

5. Jump up^ In search of lost time, Jo Marchant, Nature 444, #7119 (November 30, 2006), pp. 534–

538, doi:10.1038/444534a PMID 17136067.

6. Jump up^ Hassan, Ahmad Y.. "Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic

Engineering". Retrieved 2008-01-22

7. Jump up^ "Islam, Knowledge, and Science". University of Southern California. Retrieved 2008-01-22.

8. Jump up^ Lorch, R. P. (1976). "The Astronomical Instruments of Jabir ibn Aflah and the Torquetum". Centaurus 20 (1):

11–34. Bibcode:1976Cent...20...11L. doi:10.1111/j.1600-0498.1976.tb00214.x.

9. Jump up^ Koetsier, Teun (2001). "On the prehistory of programmable machines: musical automata, looms,

". Mechanism and Machine Theory (Elsevier) 36 (5): 589–603. doi:10.1016/S0094-114X(01)00005-2.

10. Jump up^ A 13th Century Programmable Robot, University of Sheffield

11. Jump up^ Simon Singh, The Code Book, pp. 14-20

12. Jump up^ Short history of the computer

13. Jump up^ History of Computing Science: The First Mechanical Calculator

14. Jump up^ Kidwell, Peggy Aldritch; Williams, Michael R. (1992). The Calculating Machines: Their history and

development. USA: Massachusetts Institute of Technology and Tomash Publishers., p.38-42, translated and edited

from Martin, Ernst (1925). Die Rechenmaschinen und ihre Entwicklungsgeschichte. Germany: Pappenheim. 15. Jump up^ "Charles Babbage". Encyclopedia Britannica Online Academic Edition. Encyclopedia Britannica In. Retrieved

2013-02-20.

16. Jump up^ Isaacson, Betsy. "Ada Lovelace, World's First Computer Programmer, Celebrated With Google Doodle". The

Huffington Post. http://www.huffingtonpost.com/2012/12/10/google-doodle-ada-lovelace_n_2270668.html. Retrieved

2013-02-20.

a b c 17. ^ Jump up to: Barker-Plummer, David. [. "Turing

Machines"]. The Stanford Encyclopedia of Philosophy. Retrieved 2013-02-20.

18. Jump up^ Talk given by Horst Zuse to the Computer Conservation Society at the Science Museum (London) on 18

November 2010

a b c 19. ^ Jump up to: Cragon, Harvey G. (2000). Computer Architecture and Implementation. Cambridge: Cambridge

University Press. pp. 1–13. ISBN 0521651689.

20. Jump up^ "Accumlator" Def. 3. Oxford Dictionaries. Sources[edit]

Ifrah, Georges (2001), The Universal History of Computing: From the Abacus to the Quantum Computer, New York: John Wiley & Sons, ISBN 0-471-39671-0 Further reading[edit]

 Alan Turing  A Very Brief History of Computer Science  Computer History Museum  Computers: From the Past to the Present  The First "Computer Bug" at the Online Library of the Naval Historical Center, retrieved February 28, 2006  Bitsavers, an effort to capture, salvage, and archive historical computer software and manuals from minicomputers and mainframes of the 1950s, 1960s, 1970s, and 1980s  Gordana Dodig-Crnkovic. "History of Computer Science