วันจันทร์ที่ 16 กันยายน พ.ศ. 2556

Google

Early history

Google began in March 1996 as a research project by Larry Page and Sergey Brin, Ph.D. students at Stanford[1] working on the Stanford Digital Library Project (SDLP). The SDLP's goal was “to develop the enabling technologies for a single, integrated and universal digital library" and was funded through the National Science Foundation among other federal agencies.[2][3][4] In search of a dissertation theme, Page considered—among other things—exploring the mathematical properties of the World Wide Web, understanding its link structure as a huge graph.[5] His supervisor Terry Winogradencouraged him to pick this idea (which Page later recalled as "the best advice I ever got"[6]) and Page focused on the problem of finding out which web pages link to a given page, considering the number and nature of such backlinks to be valuable information about that page (with the role of citations inacademic publishing in mind).[5] In his research project, nicknamed "BackRub", he was soon joined by Sergey Brin, a fellow Stanford Ph.D. student supported by a National Science Foundation Graduate Fellowship.[2] Brin was already a close friend, whom Page had first met in the summer of 1995 in a group of potential new students which Brin had volunteered to show around the campus.[5] Page's web crawler began exploring the web in March 1996, setting out from Page's own Stanford home page as its only starting point.[5] To convert the backlink data that it gathered into a measure of importance for a given web page, Brin and Page developed the PageRank algorithm.[5] Analyzing BackRub's output—which, for a given URL, consisted of a list of backlinks ranked by importance—it occurred to them that a search engine based on PageRank would produce better results than existing techniques (existing search engines at the time essentially ranked results according to how many times the search term appeared on a page).[5][7]
A small search engine called "RankDex" from IDD Information Services (a subsidiary of Dow Jones) designed by Robin Li was, since 1996, was already exploring a similar strategy for site-scoring and page ranking.[8] The technology in RankDex would be patented[9] and used later when Li founded Baidu in China.[10][11]
Convinced that the pages with the most links to them from other highly relevant Web pages must be the most relevant pages associated with the search, Page and Brin tested their thesis as part of their studies, and laid the foundation for their search engine. By early 1997, the backrub page described the state as follows:[12]
Some Rough Statistics (from August 29th, 1996)
Total indexable HTML urls: 75.2306 Million
Total content downloaded: 207.022 gigabytes
...
BackRub is written in Java and Python and runs on several Sun Ultras and Intel Pentiums running Linux. The primary database is kept on an Sun Ultra II with 28GB of disk. Scott Hassan and Alan Steremberg have provided a great deal of very talented implementation help. Sergey Brin has also been very involved and deserves many thanks.
-Larry Page page@cs.stanford.edu
Originally the search engine used the Stanford website with the domain google.stanford.edu. The domain google.com was registered on September 15, 1997. They formally incorporated their company, Google Inc., on September 4, 1998 at a friend's garage in Menlo Park, California.
Both Brin and Page had been against using advertising pop-ups in a search engine, or an "advertising funded search engines" model, and they wrote a research paper in 1998 on the topic while still students. However, they soon changed their minds and early on allowed simple text ads.[13]
Google Home Page September 1998
By the end of 1998, Google had an index of about 60 million pages.[14] The home page was still marked "BETA", but an article inSalon.com already argued that Google's search results were better than those of competitors like Hotbot or Excite.com, and praised it for being more technologically innovative than the overloaded portal sites (like Yahoo!, Excite.com, Lycos, Netscape'sNetcenter, AOL.com, Go.com and MSN.com) which at that time, during the growing dot-com bubble, were seen as "the future of the Web", especially by stock market investors.
In March 1999, the company moved into offices at 165 University Avenue in Palo Alto, home to several other noted Silicon Valleytechnology startups. After quickly outgrowing two other sites, the company leased a complex of buildings in Mountain View at 1600 Amphitheatre Parkway from Silicon Graphics (SGI) in 2003.] The company has remained at this location ever since, and the complex has since become known as the Googleplex (a play on the word googolplex, a number that is equal to 1 followed by a googol of zeros). In 2006, Google bought the property from SGI for US$319 million.
The Google search engine attracted a loyal following among the growing number of Internet users, who liked its simple design.[18]In 2000, Google began selling advertisements associated with search keywords.[1] The ads were text-based to maintain an uncluttered page design and to maximize page loading speed.[1] Keywords were sold based on a combination of price bid and click-throughs, with bidding starting at $.05 per click.[1] This model of selling keyword advertising was pioneered by Goto.com(later renamed Overture Services, before being acquired by Yahoo! and rebranded as Yahoo! Search Marketing).[19][20][21] While many of its dot-com rivals failed in the new Internet marketplace, Google quietly rose in stature while generating revenue.[1]
Google's declared code of conduct is "Don't be evil", a phrase which they went so far as to include in their prospectus (aka "S-1") for their 2004 IPO, noting that "We believe strongly that in the long term, we will be better served—as shareholders and in all other ways—by a company that does good things for the world even if we forgo some short term gains

Financing and initial public offering

The first funding for Google as a company was secured on August 1998 in the form of a US$100,000 contribution from Andy Bechtolsheim, co-founder of Sun Microsystems, given to a corporation which did not yet exist.[23]
On June 7, 1999, a round of equity funding totalling $25 million was announced;[24] the major investors being rival venture capital firms Kleiner Perkins Caufield & Byers and Sequoia Capital.[23]
While Google still needed more funding for their further expansion, Brin and Page were hesitant to take the company public, despite their financial issues. They were not ready to give up control over Google. After borrowing the $25 million venture capital money from Kleiner Perkins Caufield & Byers and Sequoia Capital, Sequoia forced Brin and Page to hire a CEO or else they would take back that borrowed $12.5 million. Finally, Brin and Page gave in and hired Eric Schmidt as Google’s first CEO in March 2001 and the company went public three years later.[25]
In October 2003, while discussing a possible initial public offering of shares (IPO), Microsoft approached the company about a possible partnership or merger.[26] However, no such deal ever materialized. In January 2004, Google announced the hiring of Morgan Stanley and Goldman Sachs Group to arrange an IPO. The IPO was projected to raise as much as $4 billion.

Google's initial public offering took place on August 19, 2004.[27] A total of 19,605,052 shares were offered at a price of $85 per share.[28] Of that, 14,142,135 (another mathematical reference as√2 ≈ 1.4142135) were floated by Google and 5,462,917 by selling stockholders. The sale raised US$1.67 billion, and gave Google a market capitalization of more than $23 billion.[29] Many of Google's employees became instant paper millionaires. Yahoo!, a competitor of Google, also benefited from the IPO because it owns 2.7 million shares of Google.[30]
The company is listed on the NASDAQ stock exchange under the ticker symbol GOOG.

Growth

In February 2003, Google acquired Pyra Labs, owner of Blogger, a pioneering and leading web log hosting website. Some analysts considered the acquisition inconsistent with Google's business model. However, the acquisition secured the company's competitive ability to use information gleaned from blog postings to improve the speed and relevance of articles contained in a companion product to the search engine Google News.
At its peak in early 2004, Google handled upwards of 84.7% of all search requests on the World Wide Web through its website and through its partnerships with other Internet clients like Yahoo!, AOL, and CNN. In February 2004, Yahoo! dropped its partnership with Google, providing an independent search engine of its own. This cost Google some market share, yet Yahoo!'s move highlighted Google's own distinctiveness, and today the verb "to google" has entered a number of languages (first as a slang verb and now as a standard word), meaning "to perform a web search" (a possible indication of "Google" becoming a genericized trademark).
the relationship between Google, Baidu, and Yahoo
After the IPO, Google's stock market capitalization rose greatly and the stock price more than quadrupled. On August 19, 2004 the number of shares outstanding was 172.85 million while the "free float" was 19.60 million (which makes 89% held by insiders). In January 2005 the number of shares outstanding was up 100 million to 273.42 million, 53% of that was held by insiders, which made the float 127.70 million (up 110 million shares from the first trading day). The two founders are said to hold almost 30% of the outstanding shares. The actual voting power of the insiders is much higher, however, as Google has a dual class stock structure in which each Class B share gets ten votes compared to each Class A share getting one. Page says in the prospectus that Google has "a dual class structure that is biased toward stability and independence and that requires investors to bet on the team, especially Sergey and me." The company has not reported any treasury stock holdings as of the Q3 2004 report.
On June 1, 2005, Google shares gained nearly four percent after Credit Suisse First Boston raised its price target on the stock to $350. On that same day, rumors circulated in the financial community that Google would soon be included in the S&P 500.[31] When companies are first listed on the S&P 500 they typically experience a bump in share price due to rapid accumulation of the stock within index funds that track the S&P 500. The rumors, however, were premature and Google was not added to the S&P 500 until 2006. Nevertheless, on June 7, 2005, Google was valued at nearly $52 billion, making it one of the world's biggest media companies by stock market value.
On August 18, 2005 (one year after the initial IPO), Google announced that it would sell 14,159,265 (another mathematical reference as π ≈ 3.14159265) more shares of its stock to raise money. The move would double Google's cash stockpile to $7 billion. Google said it would use the money for "acquisitions of complementary businesses, technologies or other assets".[32]
On September 28, 2005, Google announced a long-term research partnership with NASA which would involve Google building a 1,000,000-square-foot (93,000 m2) R&D center at NASA's Ames Research Center, and on December 31, 2005 Time Warner's AOL unit and Google unveiled an expanded partnership—see Partnerships below.
Additionally in 2005, Google formed a partnership with Sun Microsystems to help share and distribute each other's technologies. As part of the partnership Google will hire employees to help in the open source office program OpenOffice.org.[33]
With Google's increased size came more competition from large mainstream technology companies. One such example is the rivalry between Microsoft and Google.[34] Microsoft had been touting its Bing search engine to counter Google's competitive position. Furthermore, the two companies are increasingly offering overlapping services, such as webmail (Gmail vs. Hotmail), search (both online and local desktop searching), and other applications (for example, Microsoft's Windows Live Local competes with Google Earth). In addition to an Internet Explorer replacement Google designed its ownLinux-based operating system called Chrome OS to directly compete with Microsoft Windows. There were also rumors of a Google web browser, fueled much by the fact that Google is the owner of the domain name "gbrowser.com". These were later proven when Google released Google Chrome. This corporate feud is most directly expressed in hiring offers and defections. Many Microsoft employees who worked on Internet Explorer had left to work for Google.[citation needed] This feud boiled over into the courts when Kai-Fu Lee, a former vice-president of Microsoft, quit Microsoft to work for Google. Microsoft sued to stop his move by citing Lee's non-compete contract (he had access to much sensitive information regarding Microsoft's plans in China).
Google and Microsoft reached a settlement out of court on December 22, 2005, the terms of which are confidential.[35]
Click fraud has also become a growing problem for Google's business strategy. Google's CFO George Reyes said in a December 2004 investor conference that "something has to be done about this really, really quickly, because I think, potentially, it threatens our business model."[36] Some have suggested that Google is not doing enough to combat click fraud. Jessie Stricchiola, president of Alchemist Media, called Google "the most stubborn and the least willing to cooperate with advertisers", when it comes to click fraud.
While the company's primary market is in the web content arena, Google has also recently began to experiment with other markets, such as radio and print publications. On January 17, 2006, Google announced that it had purchased the radio advertising company dMarc, which provides an automated system that allows companies to advertise on the radio.[37] This will allow Google to combine two advertising media—the Internet and radio—with Google's ability to laser-focus on the tastes of consumers. Google has also begun an experiment in selling advertisements from its advertisers in offline newspapers and magazines, with select advertisements in the Chicago Sun-Times.[38] They have been filling unsold space in the newspaper that would have normally been used for in-house advertisements.
During the third quarter 2005 Google Conference Call, Eric Schmidt said, "We don't do the same thing as everyone else does. And so if you try to predict our product strategy by simply saying well so and so has this and Google will do the same thing, it's almost always the wrong answer. We look at markets as they exist and we assume they are pretty well served by their existing players. We try to see new problems and new markets using the technology that others use and we build."
After months of speculation, Google was added to the Standard & Poor's 500 index (S&P 500) on March 31, 2006.[39] Google replaced Burlington Resources, a major oil producer based inHouston that had been acquired by ConocoPhillips.[40] The day after the announcement Google's share price rose by 7%.[41]
Over the course of the past decade, Google has become quite well known for its corporate culture and innovative, clean products, and has had a major impact on online culture.

Name

The name "Google" originated from a misspelling of "googol",[42][43] which refers to the number represented by a 1 followed by one-hundred zeros. Page and Brin write in their original paper onPageRank:[44] "We chose our systems name, Google, because it is a common spelling of googol, or 10100 and fits well with our goal of building very large-scale search engines."
However, there are uses of the name going back at least as far as the creation of the comic strip character Barney Google in 1919. Enid Blyton used the phrase "Google Bun" in The Magic Faraway Tree (published 1941) The Folk of the Faraway Tree (published 1946),[45] and called a clown character "Google" in Circus Days Again (published 1942).[46] There is also the Googleplex Star Thinker from Douglas Adams' The Hitchhiker's Guide to the Galaxy. In March 1996 a business called Groove Track Productions applied for a United States trademark for "Google" for various products including several categories of clothing, stuffed toys, board games, and candy. The firm abandoned its application in July 1997.[47][verification needed]
Having found its way increasingly into everyday language, the verb "google" was added to the Merriam Webster Collegiate Dictionary and the Oxford English Dictionary in 2006, meaning "to use the Google search engine to obtain information on the Internet."[48][49] The use of the term itself reflects their mission to organize a seemingly infinite amount of information on the web.[43] In November 2009, the Global Language Monitor named "Google" No. 7 on its Top Words of the Decade list.[50] In December 2009 the BBC highlighted Google in their "Portrait of the Decade (Words)" series.[51] In May 2012, David Elliott filed a complaint against Google, Inc. claiming that Google’s once distinctive mark GOOGLE® has become generic and lacks trademark significance due to its common use as a transitive verb. After losing to Google in UDRP proceedings involving many “Google-related” domain name registrations that he owns, Elliott now seeks a declaratory judgment that his domain names are rightfully his, that they do not infringe any trademark rights Google may own, and that all Google’s registered GOOGLE® marks should be cancelled since “google” is now a common generic word worldwide that means “to search the Internet.”[52]

Philanthropy

In 2004, Google formed a non-profit philanthropic wing, Google.org, giving it a starting fund of $1 billion.[53] The express mission of the organization is to help with the issues of climate change(see also global warming), global public health, and global poverty. Among its first projects is to develop a viable plug-in hybrid electric vehicle that can attain 100 mpg.[54]

Acquisitions

Since 2001, Google has acquired several small companies, often consisting of innovative teams and products. One of the earlier companies that Google bought was Pyra Labs. They were the creators of Blogger, a weblog publishing platform, first launched in 1999. This acquisition led to many premium features becoming free. Pyra Labs was originally formed by Evan Williams, yet he left Google in 2004. In early 2006, Google acquired Upstartle, a company responsible for the online collaborative word processor, Writely. The technology in this product was combined with Google Spreadsheets to become Google Docs & Spreadsheets.
The logo of YouTube, which in late 2006 was acquired by Google.
On October 9, 2006, Google announced that it would buy the popular online video site YouTube for $1.65 billion[55] and maintain YouTube as a separate brand, rather than merging it with Google Video. Meanwhile, Google Video signed an agreement with Sony BMG Music Entertainment and the Warner Music Group, for both companies to deliver music videos to the site.[56] The deal was finalized by November 13, 2006.[57]
On October 31, 2006, Google announced that it had purchased JotSpot, a company that helped pioneer the market for collaborative, web-based business software to bolster its position in the online document arena.[58]
On March 17, 2007, Google announced its acquisition of two more companies. The first is Gapminder's Trendalyzer software, a company that specializes in developing information technology for provision of free statistics in new visual and animated ways[59] On the same day, Google also announced its acquisition of Adscape Media, a small in-game advertising company based in San Francisco, California.[60]

Partnerships

Google has worked with several corporations, in order to improve production and services. On September 28, 2005,Google announced a long-term research partnership with NASA which would involve Google building a 1,000,000-square-foot (93,000 m2) R&D center at NASA's Ames Research Center. NASA and Google are planning to work together on a variety of areas, including large-scale data management, massively distributed computing, bio-info-nano convergence, and encouragement of the entrepreneurial space industry. The new building would also include labs, offices, and housing for Google engineers.[61] In October 2006, Google formed a partnership with Sun Microsystems to help share and distribute each other's technologies. As part of the partnership Google will hire employees to help the open source office program OpenOffice.org.[33]
Time Warner's AOL unit and Google unveiled an expanded partnership on December 21, 2005, including an enhanced global advertising partnership and a US$1 billion investment by Google for a 5% stake in AOL.[62] As part of the collaboration, Google plans to work with AOL on video search and offer AOL's premium-video service within Google Video. This did not allow users of Google Video to search for AOL's premium-video services. Display advertising throughout the Google network will also increase.
In August 2006, Google signed a $900 million offer with News Corp.'s Fox Interactive Media unit to provide search and advertising on MySpace and other News Corp. websites including IGN,AmericanIdol.com, Fox.com, and Rotten Tomatoes, although Fox Sports is not included as a deal already exists between News Corp. and MSN.[63][64]
On December 6, 2006, British Sky Broadcasting released details of a Sky and Google alliance.[65] This includes a feature where Gmail will link with Sky and host a mail service for Sky, incorporating the email domain "@sky.com".
In 2007, Google displaced America Online as a key partner and sponsor of the NORAD Tracks Santa program.[66][67][68] Google Earth was used for the first time to give visitors to the website the impression that they were following Santa Claus' progress in 3-D.[69] The program also made its presence known on YouTube in 2007 as part of its partnership with Google.[70]
In January 2009, Google announced a partnership with the Pontifical Council for Social Communications, allowing the Pope to have his own channel on YouTube.[71]
In January 2013, Google announced a partnership with Kia Motors and Hyundai. The partnership integrates Google Maps and Place into new car models to be released later in 2013.[72]

วันจันทร์ที่ 2 กันยายน พ.ศ. 2556

Computer

Computer
Acer Aspire 8920 Gemstone by Georgy.JPGColumbia Supercomputer - NASA Advanced Supercomputing Facility.jpgIntertec Superbrain.jpg
2010-01-26-technikkrempel-by-RalfR-05.jpgThinking Machines Connection Machine CM-5 Frostburg 2.jpgG5 supplying Wikipedia via Gigabit at the Lange Nacht der Wissenschaften 2006 in Dresden.JPG
DM IBM S360.jpgAcorn BBC Master Series Microcomputer.jpgDell PowerEdge Servers.jpg
A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.
Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU) and some form ofmemory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change theorder of operations based on stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.
The first electronic digital computers were developed between 1940 and 1945. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).[1] In this era mechanical analog computers were used for military applications.
Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space.[2] Simple computers are small enough to fit into mobile devices, and mobile computers can be powered by smallbatteries. Personal computers in their various forms are icons of the Information Age and are what most people think of as “computers.” However, the embedded computers found in many devices from MP3 players to fighter aircraft and from toys to industrial robots are the most numerous.

History of computing

The Jacquard loom, on display at theMuseum of Science and Industry in Manchester, England, was one of the first programmable devices.
The first use of the word “computer” was recorded in 1613 in a book called “The yong mans gleanings” by English writer Richard Braithwait I haue read the truest computer of Times, and the best Arithmetician that euer breathed, and he reduceth thy dayes into a short number. It referred to a person who carried out calculations, or computations, and the word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations.[3]

Limited-function early computers

The history of the modern computer begins with two separate technologies, automated calculation and programmability. However no single device can be identified as the earliest computer, partly because of the inconsistent application of that term. A few devices are worth mentioning though, like somemechanical aids to computing, which were very successful and survived for centuries until the advent of the electronic calculator, like the Sumerian abacus, designed around 2500 BC[4] of which a descendant won a speed competition against a contemporary desk calculating machine in Japan in 1946,[5] theslide rules, invented in the 1620s, which were carried on five Apollo space missions, including to the moon[6] and arguably the astrolabe and theAntikythera mechanism, an ancient astronomical analog computer built by the Greeks around 80 BC.[7] The Greek mathematician Hero of Alexandria (c. 10–70 AD) built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums that might be considered to be a means of deciding which parts of the mechanism performed which actions and when.[8] This is the essence of programmability.
Blaise Pascal invented the mechanical calculator in 1642,[9] known as Pascal's calculator, it was the first machine to better human performance of arithmetical computations[10] and would turn out to be the only functional mechanical calculator in the 17th century.[11] Two hundred years later, in 1851,Thomas de Colmar released, after thirty years of development, his simplified arithmometer; it became the first machine to be commercialized because it was strong enough and reliable enough to be used daily in an office environment. The mechanical calculator was at the root of the development of computers in two separate ways. Initially, it was in trying to develop more powerful and more flexible calculators[12] that the computer was first theorized by Charles Babbage[13][14] and then developed.[15] Secondly, development of a low-cost electronic calculator, successor to the mechanical calculator, resulted in the development by Intel[16] of the first commercially availablemicroprocessor integrated circuit.

First general-purpose computers

In 1801, Joseph Marie Jacquard made an improvement to the textile loom by introducing a series of punched paper cards as a template which allowed his loom to weave intricate patterns automatically. The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.
The Most Famous Image in the Early History of Computing[17]

This portrait of Jacquard was woven in silk on a Jacquard loom and required 24,000 punched cards to create (1839). It was only produced to order. Charles Babbage owned one of these portraits; it inspired him in using perforated cards in his analytical engine.[18]
The Zuse Z3, 1941, considered the world's first working programmable, fully automatic computing machine.
It was the fusion of automatic calculation with programmability that produced the first recognizable computers. In 1837, Charles Babbage was the first to conceptualize and design a fully programmablemechanical computer, his analytical engine.[19] Limited finances and Babbage's inability to resist tinkering with the design meant that the device was never completed—nevertheless his son, Henry Babbage, completed a simplified version of the analytical engine's computing unit (the mill) in 1888. He gave a successful demonstration of its use in computing tables in 1906. This machine was given to the Science museum in South Kensington in 1910.
Ada Lovelace, considered to be the first computer programmer.[20]
Between 1842 and 1843, Ada Lovelace, an analyst of Charles Babbage's analytical engine, translated an article by Italian military engineer Luigi Menabrea on the engine, which she supplemented with an elaborate set of notes of her own, simply called Notes. These notes contain what is considered the first computer program – that is, an algorithm encoded for processing by a machine. Lovelace's notes are important in the early history of computers. She also developed a vision on the capability of computers to go beyond mere calculating or number-crunching while others, including Babbage himself, focused only on those capabilities.[21]
In the late 1880s, Herman Hollerith invented the recording of data on a machine-readable medium. Earlier uses of machine-readable media had been for control, not data. “After some initial trials with paper tape, he settled on punched cards...”[22] To process these punched cards he invented the tabulator, and the keypunch machines. These three inventions were the foundation of the modern information processing industry. Large-scale automated data processing of punched cards was performed for the 1890 United States Census by Hollerith's company, which later became the core of IBM. By the end of the 19th century a number of ideas and technologies, that would later prove useful in the realization of practical computers, had begun to appear:Boolean algebra, the vacuum tube (thermionic valve), punched cards and tape, and the teleprinter.
During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticatedanalog computers, which used a direct mechanical or electrical model of the problem as a basis forcomputation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.
Alan Turing is widely regarded as the father of modern computer science. In 1936, Turing provided an influential formalization of the concept of the algorithmand computation with the Turing machine, providing a blueprint for the electronic digital computer.[23] Of his role in the creation of the modern computer,Time magazine in naming Turing one of the 100 most influential people of the 20th century, states: “The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine.”[23]
The ENIAC, which became operational in 1946, is considered to be the first general-purpose electronic computer. Programmers Betty Jean Jennings (left) and Fran Bilas (right) are depicted here operating the ENIAC's main control panel.
EDSAC was one of the first computers to implement the stored-program (von Neumann) architecture.
The first really functional computer was the Z1, originally created by Germany's Konrad Zuse in his parents living room in 1936 to 1938, and it is considered to be the first electro-mechanical binary programmable (modern) computer.[24]
George Stibitz is internationally recognized as a father of the modern digital computer. While working at Bell Labs in November 1937, Stibitz invented and built a relay-based calculator he dubbed the “Model K” (for “kitchen table,” on which he had assembled it), which was the first to usebinary circuits to perform an arithmetic operation. Later models added greater sophistication including complex arithmetic and programmability.[25]
The Atanasoff–Berry Computer (ABC) was the world's first electronic digital computer, albeit not programmable.[26] Atanasoff is considered to be one of the fathers of the computer.[27] Conceived in 1937 by Iowa State College physics professor John Atanasoff, and built with the assistance of graduate student Clifford Berry,[28] the machine was not programmable, being designed only to solve systems of linear equations. The computer did employ parallel computation. A 1973 court ruling in a patent dispute found that the patent for the 1946 ENIAC computer derived from the Atanasoff–Berry Computer.
The first program-controlled computer was invented by Konrad Zuse, who built the Z3, an electromechanical computing machine, in 1941.[29] The first programmable electronic computer was the Colossus, built in 1943 by Tommy Flowers.

Key steps towards modern computers

A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features that are seen in modern computers. The use of digital electronics (largely invented by Claude Shannon in 1937) and more flexible programmability were vitally important steps, but defining one point along this road as “the first digital electronic computer” is difficult.Shannon 1940 Notable achievements include:
  • Konrad Zuse's electromechanical “Z machines.” The Z3 (1941) was the first working machine featuring binary arithmetic, including floating point arithmetic and a measure of programmability. In 1998 the Z3 was proved to be Turing complete, therefore being the world's first operational computer.[30] Thus, Zuse is often regarded as the inventor of the computer.[31][32][33][34]
  • The non-programmable Atanasoff–Berry Computer (commenced in 1937, completed in 1941) which used vacuum tube based computation, binary numbers, and regenerative capacitor memory. The use of regenerative memory allowed it to be much more compact than its peers (being approximately the size of a large desk or workbench), since intermediate results could be stored and then fed back into the same set of computation elements.
  • The secret British Colossus computers (1943),[35] which had limited programmability but demonstrated that a device using thousands of tubes could be reasonably reliable and electronically re-programmable. It was used for breaking German wartime codes.
  • The Harvard Mark I (1944), a large-scale electromechanical computer with limited programmability.[36]
  • The U.S. Army's Ballistic Research Laboratory ENIAC (1946), which used decimal arithmetic and is sometimes called the first general purposeelectronic computer (since Konrad Zuse's Z3 of 1941 used electromagnets instead of electronics). Initially, however, ENIAC had an architecture which required rewiring a plugboard to change its programming.

Stored-program architecture

Several developers of ENIAC, recognizing its flaws, came up with a far more flexible and elegant design, which came to be known as the “stored-program architecture” or von Neumann architecture. This design was first formally described by John von Neumann in the paper First Draft of a Report on the EDVAC, distributed in 1945. A number of projects to develop computers based on the stored-program architecture commenced around this time, the first of which was completed in 1948 at the University of Manchester in England, the Manchester Small-Scale Experimental Machine (SSEM or “Baby”). The Electronic Delay Storage Automatic Calculator (EDSAC), completed a year after the SSEM at Cambridge University, was the first practical, non-experimental implementation of the stored-program design and was put to use immediately for research work at the university. Shortly thereafter, the machine originally described by von Neumann's paper—EDVAC—was completed but did not see full-time use for an additional two years.
Nearly all modern computers implement some form of the stored-program architecture, making it the single trait by which the word “computer” is now defined. While the technologies used in computers have changed dramatically since the first electronic, general-purpose computers of the 1940s, most still use the von Neumann architecture.
Die of an Intel 80486DX2 microprocessor(actual size: 12×6.75 mm) in its packaging
Beginning in the 1950s, Soviet scientists Sergei Sobolev and Nikolay Brusentsov conducted research on ternary computers, devices that operated on a base three numbering system of -1, 0, and 1 rather than the conventional binary numbering system upon which most computers are based. They designed the Setun, a functional ternary computer, at Moscow State University. The device was put into limited production in the Soviet Union, but supplanted by the more common binary architecture.

Semiconductors and microprocessors

Computers using vacuum tubes as their electronic elements were in use throughout the 1950s, but by the 1960s they had been largely replaced bytransistor-based machines, which were smaller, faster, cheaper to produce, required less power, and were more reliable. The first transistorized computer was demonstrated at the University of Manchester in 1953.[37] In the 1970s, integrated circuit technology and the subsequent creation ofmicroprocessors, such as the Intel 4004, further decreased size and cost and further increased speed and reliability of computers. By the late 1970s, many products such as video recorders contained dedicated computers called microcontrollers, and they started to appear as a replacement to mechanical controls in domestic appliances such as washing machines. The 1980s witnessed home computers and the now ubiquitous personal computer. With the evolution of the Internet, personal computers are becoming as common as the television and the telephone in the household.[citation needed]
Modern smartphones are fully programmable computers in their own right, and as of 2009 may well be the most common form of such computers in existence.[citation needed]

Programs

Alan Turing was an influential computer scientist.
The defining feature of modern computers which distinguishes them from all other machines is that they can be programmed. That is to say that some type of instructions (the program) can be given to the computer, and it will process them. Modern computers based on the von Neumann architectureoften have machine code in the form of an imperative programming language.
In practical terms, a computer program may be just a few instructions or extend to many millions of instructions, as do the programs for word processors and web browsers for example. A typical modern computer can execute billions of instructions per second (gigaflops) and rarely makes a mistake over many years of operation. Large computer programs consisting of several million instructions may take teams of programmers years to write, and due to the complexity of the task almost certainly contain errors.

Stored program architecture

Replica of the Small-Scale Experimental Machine (SSEM), the world's first stored-program computer, at the Museum of Science and Industry in Manchester, England
This section applies to most common RAM machine-based computers.
In most cases, computer instructions are simple: add one number to another, move some data from one location to another, send a message to some external device, etc. These instructions are read from the computer's memory and are generally carried out (executed) in the order they were given. However, there are usually specialized instructions to tell the computer to jump ahead or backwards to some other place in the program and to carry on executing from there. These are called “jump” instructions (or branches). Furthermore, jump instructions may be made to happen conditionally so that different sequences of instructions may be used depending on the result of some previous calculation or some external event. Many computers directly support subroutines by providing a type of jump that “remembers” the location it jumped from and another instruction to return to the instruction following that jump instruction.
Program execution might be likened to reading a book. While a person will normally read each word and line in sequence, they may at times jump back to an earlier place in the text or skip sections that are not of interest. Similarly, a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met. This is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention.
Comparatively, a person using a pocket calculator can perform a basic arithmetic operation such as adding two numbers with just a few button presses. But to add together all of the numbers from 1 to 1,000 would take thousands of button presses and a lot of time, with a near certainty of making a mistake. On the other hand, a computer may be programmed to do this with just a few simple instructions. For example: