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John Dvorak

John Dvorak

:For the inventor of the Dvorak Simplified Keyboard, see August Dvorak. August Dvorak John C. Dvorak is an American columnist writing on technology, specifically that relating to computing. His writing extends back to the 1980s, when he was a mainstay of a variety of magazines. More recently he has become known for his somewhat more speculative and provocative articles. He writes for various publications, including PC Magazine (two columns since 1986), Marketwatch, BUG Magazine (Croatia), and Info Exame (Brazil). Dvorak has been a columnist for Boardwatch Magazine, Forbes, Forbes Online, MacUser, MicroTimes, PC/Computing, Barron's Magazine, Smart Business, and Vancouver Sun. (The MicroTimes column ran under the banner Dvorak's Last Column.) He is the creator and lead judge of the Dvorak Awards (1992 - 1997). He has written or co-authored over a dozen books, including Hypergrowth: The Rise and Fall of the Osborne Computer Corporation with Adam Osborne. His current book is Online! The Book (Prentice Hall PTR, October, 2003) with co-authors Wendy Taylor and Chris Pirillo. The Computer Press Association presented Dvorak with the Best Columnist and Best Column awards, and he was also the 2004 and 2005 award winner of the American Business Editors Association's national gold award for best online column of 2003 and 2004 respectively. He was on the original start-up team for C-Net Networks, appearing on the television show C-Net Central. He also hosted a radio show called Real Computing on NPR, as well as a television show on TechTV called Silicon Spin. He now appears on Marketwatch TV and is a regular panelist on This Week in Tech, a podcast featuring many other former hosts from TechTV including Leo Laporte and Patrick Norton. In addition, he maintains a blog entitled [http://www.dvorak.org/blog/ Dvorak Uncensored] which contains commentary on news articles, industry trends, and links to otherwise notable web pages. Dvorak has been a longtime critic of Apple Computer, even during his stint as a columnist for MacUser magazine. In 2005 he suggested that recent good press about Apple was due to media bias: "With 90 percent of the mainstream writers being Mac users, what would you expect?" he wrote. In a 2005 [http://thisweekintech.com/18 This Week in Tech podcast] he claimed that, thanks to his hosting provider, he "gets no spam". This became a short-lived catchphrase and half-hearted chant among the audience. No mention was made of his false positive rate (how much legitimate mail gets inappropriately deleted).

External links


- [http://www.dvorak.org/blog/ John C. Dvorak's blog]
- [http://www.pcmag.com/category2/0,1874,3574,00.asp John C. Dvorak's Column - PC Magazine]
- [http://www.pcmag.com/category2/0,1874,1103,00.asp John C. Dvorak's Inside Track - PC Magazine]
- [http://www.marketwatch.com/news/newsfinder/default.asp?Property=column&value=JOHN+DVORAK%27S+SECOND+OPINION&scid=3&siteid=google&dist=googlemore John C. Dvorak's Second Opinion - MarketWatch] Dvorak, John C. Dvorak, John C.

Dvorak Simplified Keyboard

The Dvorak Simplified Keyboard (pronounced ) is a keyboard layout designed by Drs. August Dvorak and William Dealey in the 1920s and 1930s as an alternative to the more common QWERTY layout. It has also been called the Simplified Keyboard or American Simplified Keyboard, but is commonly known as the Dvorak keyboard.

Overview

Dvorak and Dealey studied letter frequencies and the physiology of the hand and created the layout to adhere to these principles:
- It is easier to type letters alternating between hands.
- For maximum speed and efficiency, the most common letters and digraphs should be the easiest to type. This means that they should be on the home row, which is where the fingers rest.
- Likewise, the least common letters should be on the bottom row, which is the hardest row to reach.
- The right hand should do more of the typing, because most people are right-handed.
- It is more difficult to type digraphs with adjacent fingers than non-adjacent fingers.
- Stroking should generally move from the edges of the board to the middle (as an example, rap your fingers on a table and see which is easier: going from little finger to index or vice versa). This motion on a keyboard is called inboard stroke flow. The layout was completed in 1932 and was granted in 1936. It was designated an alternate standard keyboard layout by the American National Standards Institute (ANSI) in 1982. In 1984 the Dvorak keyboard had an estimated 100,000 users. Also, due to some of the above principles and other preferences, there is considerable variation between implementations in the placement of punctuation on the English layout.

Resistance to change

Even though many feel that the principles on which the Dvorak keyboard is based should make it superior to the older QWERTY, there is divergent evidence about whether the logic of the keyboard actually translates into faster typing. Although studies performed by Dvorak and his disciples indicate a large advantage in typing speed (40%), other studies performed for the US General Services Administration and independent ergonomics investigations indicate either a small or nonexistent advantage (less than 5%). Certainly, attempts to universally convert to the Dvorak have not been met with success. Typists who are already proficient with the QWERTY layout do not want to have to relearn on a new keyboard, although Dvorak claimed that it didn't take very long to show an improvement. In addition to the time required for a QWERTY typist to learn the Dvorak layout and become efficient when using it, keyboard shortcuts and applications requiring key position layout will be different in the Dvorak layout and may require further training. For example, many programs use the keys H, J, K, and L to cause movement to the left, down, up, and to the right, respectively – with a non-QWERTY layout, the intended pattern disappears (although J and K stay together and in the same order). Sometimes the keys A, S, W and D are used for those movements, which are even harder to cope with when using the Dvorak layout. A discussion of the Dvorak Keyboard is sometimes used as an exercise by management consultants to illustrate the difficulties of change. Dvorak may be better suited for situations where block-typing is done. However, the design has made some headway, with Dvorak layouts now available on most major computer operating systems. It is possible, at least for some, to learn to use the Dvorak keyboard for touch typing while still retaining the ability to touch-type QWERTY. [http://web.mit.edu/jcb/www/Dvorak/]

Further improvements

NOTE: correctness of the layout shown here is in question. Software-based layout from Microsoft Windows apparently had a slightly different arrangement than the pictures shown here. In the Microsoft version, the number keys are in 2 columns only. touch typing touch typing Dvorak also proposed an alternative ordering of the digits on the numbers row, 7-5-3-1-9-0-2-4-6-8, believing this arrangement to be more efficient. However, few who use the keyboard employ this rearrangement, and indeed the ANSI standard calls for the usual numerical order. There are also Dvorak arrangements designed for one-handed typing that are useful for the disabled or for simultaneously controlling a mouse. One arrangement is designed for right-hand typing, while the other is for left-handed typing.

Other languages

In addition, Dvorak-based keyboard layouts have been created for languages other than English. An implementation for Swedish, known as Svorak, places the three extra Swedish vowels on the leftmost three keys of the upper row, which correspond to punctuation symbols on the English Dvorak layout. These punctuation symbols are then juggled with other keys, and the Alt-Gr key is required to access some of them. Another Swedish version is Svdvorak that keeps the punctuation symbols as they were in the english version. The first extra vowel (å) is placed in the far left of the top row while the other two (ä and ö) are placed at the far left of the bottom row The Norwegian implementation (known as "Norsk Dvorak") is similar to Svdvorak with "æ" and "ø" replacing "ä" and "ö". A Finnish DAS keyboard layout follows many of Dvorak's design principles, but the layout is an original design based on the most common letters and letter combinations in the Finnish language. Matti Airas has also made another layout for Finnish. Finnish can also be typed reasonably well with the English Dvorak layout if the letters ä and ö are added. There is a Brazilian ABNT2 layout for Windows and Linux, called BRDK. The most common German Dvorak is the German Type II layout. It is available for Windows, Linux, and Mac OS X.

Controversy

The Dvorak keyboard is often used as a standard example of network effect(s), particularly in economics textbooks, the other standard example being the competition between Betamax and VHS. These examples (particularly QWERTY) are also used to demonstrate that inferior products might get locked-in to the market. Liebowitz and Margolis, two economists who have investigated these claims in several academic and popular papers, argue that the actual evidence in these cases do not support a claim of Market Failure or lock-in. In circumstances where profits are unavailable to entrepreneurs who lead consumers to better choices, they agree that mistakes might be made, such as in the choice of institutions or languages. This has led to a series of articles and books that attempt, among other things, to dispute the evidence for the alleged superiority of Betamax and Dvorak. In academic circles their version of the QWERTY story is generally accepted since no one has successfully attacked it.

See also


- Repetitive strain injury
- Velotype
- Path dependence
- Maltron keyboard

External links


- [http://www.gigliwood.com/abcd/ A Basic Course in Dvorak] - by Dan Wood
- [http://dvorak.nl/learn.plp An Online Course in Dvorak] - You don't need to change your layout to Dvorak to use this.
- [http://www.dvorak-keyboard.com/ The Dvorak Keyboard - A Brief Primer] - by journalist Randy Cassingham
- [http://www.theworldofstuff.com/dvorak The Dvorak Keyboard and You] - More information about the Dvorak keyboard and how to switch
- [http://www.mwbrooks.com/dvorak/ Introducing the Dvorak Keyboard] - with many additional links
- [http://www.zigzagworld.com/HKTutor/ Hebrew Keyboard Tutor] - Shows several keyboard layouts -- good for comparing various keyboards
- [http://www.ilovejackdaniels.com/dvorak/dvorak-vs-qwerty/ Dvorak vs. Qwerty] - A comparison of the two keyboard layouts
- [http://www.dvzine.org/ DvZine.org] - A website advocating the Dvorak layout with webcomics and zine

Dvorak tools


- [http://www.siteuri.ro/dvorak/contester.php QWERTY to Dvorak converter] - a Java applet that will convert the input in real time and test your typing speed
- [http://www.zeug.us/dvorak.php QWERTY to Dvorak converter] - Use dvorak on a qwerty keyboard, and convert between them
- [http://wbic16.xedoloh.com/dvorak.html QWERTY to Dvorak converter] - Use this to convert already-typed blocks of text
- [http://www.acm.vt.edu/~jmaxwell/dvorak/keyboard.html Keyboard Compare Applet for Dvorak and Qwerty Keyboards] (on Jon A. Maxwell's site)
- [http://www.siteuri.ro/dvorak/ Dvorak vs QWERTY Tool] - A tool to compare the efficiency of the two keyboard layouts
- [http://sourceforge.net/project/showfiles.php?group_id=8799 Dvorak Assistant] - Free Windows utility to toggle Qwerty/Dvorak without administrative access or modifying system settings
- [http://leetkey.mozdev.org LeetKey Firefox extension] - This Firefox extension supports Dvorak keyboard layout
- [http://www.microsoft.com/globaldev/tools/msklc.mspx Microsoft Keyboard Layout Creator] to design one's own layout

Evidence


- [http://www.acm.vt.edu/~jmaxwell/dvorak/comparePage.html Dvorak and Qwerty Finger Movement Distances]
- [http://www.shiar.org/happy/txts/dvorak.php Words Possible on Dvorak and Qwerty Layout Rows]

Controversy


- [http://www.geocities.com/malibu_malv/curse_qwerty.html The Curse of Qwerty] by Jared Diamond provides the traditional story of the history of the typewriter including the claim of superiority of the Dvorak keyboard.
- [http://www.utdallas.edu/~liebowit/keys1.html The Fable of the Keys] - Article by Liebowitz and Margolis questioning the Dvorak keyboard's superiority.
  - [http://www.mwbrooks.com/dvorak/dissent.html The Fable of the Fable] - Web page questioning the credibility of Fable of the Keys.
- [http://asetion.com/ Asetion] - Comparative table of the Dvorak and Asetion layouts, highlighting some of the issues with the Dvorak layout.
- [http://reason.com/9606/Fe.QWERTY.shtml Typing Errors] - Article in Reason Magazine by Liebowitz and Margolis alleging evidence against the Dvorak layout's superiority.
  - [http://www.dvorak-keyboard.com/dvorak2.html Cassingham letter] Letter to the editor of Reason Magazine by Randy Cassingham criticizing the claims made by Liebowitz and Margolis.
  - [http://www.mises.org/story/407 Market failure again?] an article of Gene Callahan in defense of the free market, stating that the Dvorak-technology was not technologically superior.

Foreign language layouts


- [http://lingvo.org/tajpu Esperanto Dvorak layout] (simple variant, no dead keys)
- [http://www.stenling.no/dvorak/ Norsk Dvorak layout]
- [http://www.iki.fi/hyvatti/dvorak/ Finnish letters ä and ö added to standard Dvorak layout]
- [http://www.students.tut.fi/~seres/DAS_en.html Finnish DAS layout]
- [http://mairas.net/projects/nappaimisto.php Finnish Matti Airas layout]
- [http://oui.com.br/n/content.php?article.17 BRDK] Linux & Windows drivers and information
- [http://www.stud.uni-hamburg.de/users/conitzer/ German Type II layout for Windows], [http://rffr.de/dvorak Linux] and [http://www.halibrand.de/dvorak/ MacOS X]
- [http://www.algo.be/ergo/dispositions.htm Dvorak-fr], a French original layout based on the characters and digrams frequencies in the French language
- [http://idvorak.altervista.org iDvorak]: Italian Dvorak layout
- [http://www.shiar.org/happy/txts/dvoraklv.php SHIAR.org], Spanish, German, Dutch, Norwegian, Swedish and Esperanto Dvorak layouts
- [http://inner.geek.nz/projects/maori-dvorak/ New Zealand/Aotearoa Māori Dvorak layout]
- [http://keyboards.jargon-file.org/#UKD UK], [http://keyboards.jargon-file.org/#USID United States-International], and [http://keyboards.jargon-file.org/#LAT9D US One-Hand Latin-9] Dvorak layouts for Windows.
- A proposal for a [http://people.musc.edu/~adelmaas/Adelmanian_keyboard/ Hebrew optimized layout] Category:Computer keyboards Category:Ergonomics ja:Dvorak配列

August Dvorak

:For the technology columnist, see John C. Dvorak. Dr. August Dvorak (May 5, 1894 – October 10, 1975) was an educational psychologist and professor of education at the University of Washington in Seattle, Washington. He and his brother-in-law, Dr William Dealey, are best known for creating the Dvorak Simplified Keyboard layout in the 1930s as a replacement for the QWERTY keyboard layout. In the 1940s, Dvorak designed keyboard layouts for people with the use of one hand. Dr. Dvorak, along with Dealey, Nellie Merrick, and Gertrude Ford, wrote the book Typewriting Behavior, which was published in 1936. The book, which has been out of print since then, is an in-depth report on the psychology and physiology of typing. Dr. Dvorak was distantly related to the Czech composer Antonín Dvořák. It is worth noting that while the composer's name is pronounced (IPA), August Dvorak's family in the U.S. pronounces it as ]. Dvorak, August Dvorak, August

US

:For alternative meanings, see the disambiguation page for US, USA, United States, or American. The United States of America is a federal democratic republic situated primarily in central North America. It comprises 50 states and one federal district, and has several territories. It is also referred to, with varying formality, as the United States, the U.S., the U.S.A., the States, or simply and most commonly, America. The official founding date of the United States is July 4, 1776, when the Second Continental Congress—representing thirteen British colonies—adopted the Declaration of Independence. However, the structure of the government was profoundly changed in 1788, when the states replaced the Articles of Confederation with the United States Constitution. The date on which each of the fifty states adopted the Constitution is typically regarded as the date that state "entered the Union" (became part of the United States). Since the mid-20th century, following World War II, the United States has emerged as a dominant global influence in economic, political, military, scientific, technological, and cultural affairs.

Geography and climate

The United States shares land borders with Canada (to the north) and Mexico (to the south), and territorial water boundaries with Canada, Russia, the Bahamas, and numerous smaller nations. It is otherwise bounded by the Pacific Ocean and the Bering Sea, in the west; the Arctic Ocean, in the northernmost areas; and the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, in the eastern and southeastern areas. Forty-eight of the states are in the single region between Canada and Mexico; this group is referred to, with varying precision and formality, as the continental or contiguous United States, sometimes abbreviated CONUS, and as the Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada. The archipelago of Hawaii is in the Pacific Ocean. The capital city, Washington, District of Columbia is a federal district located on land donated by the state of Maryland. (Virginia also donated land, but it was returned in 1847.) The United States also has overseas territories with varying levels of independence and organization. When inland water is included in the total area, only Russia and Canada are larger than the United States; if inland water is excluded, China ranks third and the U.S. ranks fourth. The United States' total area is 3,718,711 square miles (9,631,418 km²), of which land makes up 3,537,438 square miles (9,161,923 km²) and water makes up 181,273 square miles (469,495 km²). The United States' landscape is one of the most varied among those of the world's nations: among its many features are temperate forestland and rolling hills, on the east coast; mangrove, in Florida; the Great Plains, in the center of the country; the Mississippi–Missouri river system; the Great Lakes, four of the five of which are shared with Canada; the Rocky Mountains, west of the Great Plains; deserts and temperate coastal zones, west of the Rocky Mountains; and temperate rain forests, in the Pacific northwest. Alaska's tundra, and the volcanic, tropical islands of Hawaii add to the geographic diversity. Hawaii The climate varies along with the landscape, from tropical in Hawaii and southern Florida to tundra in Alaska and atop some of the highest mountains. Most of the North and East experience a temperate continental climate, with warm summers and cold winters. Most of the South experiences a subtropical humid climate with mild winters and long, hot, humid summers. Rainfall decreases markedly from the humid forests of the Eastern Great Plains to the semi-arid shortgrass prairies on the high plains abutting the Rocky Mountains. Arid deserts, including the Mojave, extend through the lowlands and valleys of the southwest, from westernmost Texas to California and northward throughout much of Nevada. Some parts of California have a Mediterranean climate. Rainforests line the windward mountains of the Pacific Northwest from Oregon to Alaska.

History

American history started with the migration of people from Asia across the Bering land bridge approximately 12,000 years ago following large animals that they hunted into the Americas. These Native Americans left evidence of their presence in petroglyphs, burial mounds, and other artifacts. It is estimated that 2-9 million people lived in the territory now occupied by the U.S. before European contact, and the subsequent introduction of foreign diseases such as small pox that greatly diminished the native populations. Some advanced societies were the Anasazi of the southwest, who inhabited Chaco Canyon, and the Woodland Indians, who built Cahokia, located near present-day St Louis, a city with a population of 40,000 at its peak in AD 1200. Vikings first visited North America around 1000, but did not settle permanently. Following the discovery voyages of Christopher Columbus around 1492, other Europeans began to explore and settle there. During the 1500s and 1600s, the Spanish settled parts of the present-day Southwest and Florida, founding St. Augustine, Florida in 1565 and Santa Fe (in what is now New Mexico) in 1607. The first successful English settlement was at Jamestown, Virginia, also in 1607. Within the next two decades, several Dutch settlements, including New Amsterdam (the predecessor to New York City), were established in what are now the states of New York and New Jersey. In 1637, Sweden established a colony at Fort Christina (in what is now Delaware), but lost the settlement to the Dutch in 1655. This was followed by extensive British settlement of the east coast. The British colonists remained relatively undisturbed by their home country until after the French and Indian War, when France ceded Canada and the Great Lakes region to Britain. Britain then imposed taxes on the 13 colonies, widely regarded by the colonists as unfair because they were denied representation in the British Parliament. Tensions between Britain and the colonists increased, and the thirteen colonies eventually rebelled against British rule. British Parliament, George Washington (1789-1797).]] In 1776, the 13 colonies split from Great Britain and formed the United States, the world's first constitutional and democratic federal republic, after their Declaration of Independence of that year, and the Revolutionary War (1775 to 1783). The original political structure was a confederation in 1777, ratified in 1781 as the Articles of Confederation. After long debate, this was supplanted by the Constitution in 1789, forming a more centralized federal government. Prior to all these was the Albany Congress in 1754, in which a union was first seriously proposed. From early colonial times, there was a shortage of labor, which encouraged unfree labor, particularly indentured servitude and slavery. In the mid-19th century, a major division occurred in the United States over the issue of states' rights and the expansion of slavery. The northern states had become opposed to slavery, while the southern states saw it as necessary for the continued success of southern agriculture and wanted it expanded to the territories. Several federal laws were passed in an attempt to settle the dispute, including the Missouri Compromise and the Compromise of 1850. The dispute reached a crisis in 1861, when seven southern states seceded1 from the Union and formed the Confederate States of America, leading to the Civil War. Soon after the war began, four more southern states seceded. During the war, Abraham Lincoln issued the Emancipation Proclamation, mandating the freedom of all slaves in states in rebellion, though full emancipation did not take place until after the end of the war in 1865, the dissolution of the Confederacy, and the Thirteenth Amendment took effect. The Civil War effectively ended the question of a state's right to secede, and is widely accepted as a major turning point after which the federal government became more powerful than state governments. Thirteenth Amendment). The title of the painting, from a 1726 poem by Bishop Berkeley, was a phrase often quoted in the era of Manifest Destiny, expressing a widely held belief that civilization had steadily moved westward throughout history. [http://americanart.si.edu/t2go/1lw/1931.6.1.html (more)] ]] During the 19th century, many new states were added to the original 13 as the nation expanded across the continent. Manifest Destiny was a philosophy that encouraged westward expansion in the United States. As the population of the Eastern states grew and as a steady increase of immigrants entered the country, settlers moved steadily westward across North America. In the process, the U.S. displaced most American Indian nations. This displacement of American Indians continues to be a matter of contention in the U.S. with many tribes attempting to assert their original claims to various lands. In some areas American Indian populations were reduced by foreign diseases contracted through contact with European settlers, and US settlers acquired those emptied lands. In other instances American Indians were removed from their traditional lands by force. Though some would say the U.S. was not a colonial power until the Spanish-American War when it acquired Puerto Rico, Guam and the Philippines, the dominion exercised over land in North America the United States claimed is essentially colonial. The Philippines became independent in 1946. During this period, the nation also became an industrial power. This continued into the 20th century, which has been termed "the American Century" because of the nation's overriding influence on the world. The US became a center for innovation and technological development; major technologies that America either developed or was greatly involved in improving include the telephone, television, computer, the Internet, nuclear weapons, nuclear power, aviation, and aeronautics. In addition to the Civil War, another major traumatic experience for the nation was the Great Depression (1929 to 1939). The nation has also taken part in several major foreign wars, including World War I and World War II (in both of which the US later joined the Allies). During the Cold War, the US was a major player in the Korean War and Vietnam War, and, along with the Soviet Union, was considered one of the world's two "superpowers". With the collapse of the Soviet Union, the US emerged as the world's leading economic and military power. Beginning in the 1990s, the United States became very involved in police actions and peacekeeping, including actions in Kosovo, Haiti, Somalia and Liberia, and the first Persian Gulf War driving Iraq out of Kuwait. After attacks on the World Trade Center and the Pentagon on September 11, 2001, the United States and other allied nations found themselves involved in what has come to be called the "War on Terrorism," which has primarily encompassed military actions in both Afghanistan and Iraq.

Government

Iraq of the United States.]]

Republic and suffrage

The United States is an example of a constitutional republic, with a government composed of and operating through a set of limited powers imposed by its design and enumerated in the United States Constitution. Specifically, the nation operates as a presidential democracy. There are three levels of government: federal, state, and local. Officials of each of these levels are either elected by eligible voters via secret ballot or appointed by other elected officials. Americans enjoy almost universal suffrage from the age of 18 regardless of race, sex, or wealth. There are some limits, however: felons are disenfranchised and in some states former felons are likewise. Furthermore, the national representation of territories and the federal district of Washington, DC in Congress is limited: residents of the District of Columbia are subject to federal laws and federal taxes but their only Congressional representative is a non-voting delegate.

Federal government

The federal government is the national government, comprising the Legislative Branch (led by Congress), the Executive Branch (led by the President), and the Judicial Branch (led by the Supreme Court). These three branches were designed to apply checks and balances on each other. The Constitution limits the powers of the federal government to defense, foreign affairs, the issuing and management of currency, the management of trade and relations between the states, and the protection of human rights. In addition to these explicitly stated powers, the federal government—with the assistance of the Supreme Court—has gradually extended these powers into such areas as welfare and education, on the basis of the "necessary and proper" clause of the Constitution.

The Congress

necessary and proper The Congress of the United States is the legislative branch of the federal government of the United States. It is bicameral, comprising the House of Representatives and the Senate. The House of Representatives consists of 435 members, each of whom represents a congressional district and serves for a two-year term. House seats are apportioned among the states by population; in contrast, each state has two Senators, regardless of population. There are a total of 100 senators, who serve six-year terms. The powers of Congress are limited to those enumerated in the Constitution; all other powers are reserved to the states and the people. The Constitution also includes the necessary-and-proper clause, which grants Congress the power to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers."

The President

necessary-and-proper clause At the top level of the executive branch is the President of the United States. The President and Vice-President are elected as 'running mates' for four-year terms by the Electoral College, for which each state, as well as the District of Columbia, is allocated a number of seats based on its representation (or ostensible representation, in the case of D. C.) in both houses of Congress (see U.S. Electoral College). The relationship between the President and the Congress reflects that between the English monarchy and parliament at the time of the framing of the United States Constitution. Congress can legislate to constrain the President's executive power, even with respect to his or her command of the armed forces; however, this power is used only very rarely—a notable example was the constraint placed on President Richard Nixon's strategy of bombing Cambodia during the Vietnam War. The President cannot directly propose legislation, and must rely on supporters in Congress to promote his or her legislative agenda. The President's signature is required to turn congressional bills into law; in this respect, the President has the power—only occasionally used—to veto congressional legislation. Congress can override a presidential veto with a two-thirds majority vote in both houses. The ultimate power of Congress over the President is that of impeachment or removal of the elected President through a House vote, a Senate trial, and a Senate vote. The threat of using this power has had major political ramifications in the cases of Presidents Andrew Johnson, Richard Nixon, and Bill Clinton. The President makes around 2,000 executive appointments, including members of the Cabinet and ambassadors, which must be approved by the Senate; the President can also issue executive orders and pardons, and has other Constitutional duties, among them the requirement to give a State of the Union address to Congress once a year. Although the President's constitutional role may appear to be constrained, in practice, the office carries enormous prestige that typically eclipses the power of Congress: the Presidency has justifiably been referred to as 'the most powerful office in the world'. The Vice President is first in the line of succession, and is the President of the Senate ex officio, with the ability to cast a tie-breaking vote. The members of the President's Cabinet are responsible for administering the various departments of state, including the Department of Defense, the Justice Department, and the State Department. These departments and department heads have considerable regulatory and political power, and it is they who are responsible for executing federal laws and regulations. George W. Bush is the 43rd President, currently serving his second term.

The Courts

George W. Bush The highest court is the Supreme Court, which consists of nine justices. The court deals with federal and constitutional matters, and can declare legislation made at any level of the government as unconstitutional, nullifying the law and creating precedent for future law and decisions. Below the Supreme Court are the courts of appeals, and below them in turn are the district courts, which are the general trial courts for federal law. Separate from, but not entirely independent of, this federal court system are the individual court systems of each state, each dealing with its own laws and having its own judicial rules and procedures. A case may be appealed from a state court to a federal court only if there is a federal question; the supreme court of each state is the final authority on the interpretation of that state's laws and constitution.

State and local governments

supreme court of each state. Note that Alaska and Hawaii are shown at different scales, and that the Aleutian Islands and the uninhabited Northwestern Hawaiian Islands are omitted from this map.]] The state governments have the greatest influence over people's daily lives. Each state has its own written constitution and has different laws. There are sometimes great differences in law and procedure between the different states, concerning issues such as property, crime, health, and education. The highest elected official of each state is the Governor. Each state also has an elected legislature (bicameral in every state except Nebraska), whose members represent the different parts of the state. Of note is the New Hampshire legislature, which is the third-largest legislative body in the English-speaking world, and has one representative for every 3,000 people. Each state maintains its own judiciary, with the lowest level typically being county courts, and culminating in each state supreme court, though sometimes named differently. In some states, supreme and lower court justices are elected by the people; in others, they are appointed, as they are in the federal system. The institutions that are responsible for local government are typically town, city, or county boards, making laws that affect their particular area. These laws concern issues such as traffic, the sale of alcohol, and keeping animals. The highest elected official of a town or city is usually the mayor. In New England, towns operate directly democratically, and in some states, such as Rhode Island and Connecticut, counties have little or no power, existing only as geographic distinctions. In other areas, county governments have more power, such as to collect taxes and maintain law enforcement agencies.

Political divisions

With the Declaration of Independence, the thirteen colonies proclaimed themselves to be nation states modeled after the European states of the time. Although considered as sovereigns initially, under the Articles of Confederation of 1781 they entered into a "Perpetual Union" and created a fully sovereign federal state, delegating certain powers to the national Congress, including the right to engage in diplomatic relations and to levy war, while each retaining their individual sovereignty, freedom and independence. But the national government proved too ineffective, so the administrative structure of the government was vastly reorganized with the United States Constitution of 1789. Under this new union, the continued status of the individual states as sovereign nation states fell into dispute in 1861, as several states attempted to secede from the union; in response, then-President Abraham Lincoln claimed that such secession was illegal, and the result was the American Civil War. Since the Union victory in 1865, the independent status of the individual states has not been broached again by any state, and the status of each state within the union has been deemed by mainstream officials and academics to be settled as being subordinate to the union as a whole. In subsequent years, the number of states grew steadily due to western expansion, the purchase of lands by the national government from other nation states, and the subdivision of existing states, resulting in the current total of 50. The states are generally divided into smaller administrative regions, including counties, cities and townships. The United States–Canadian border is the longest undefended political boundary in the world. The U.S. is divided into three distinct sections:
- the "continental United States," also known as "the Lower 48" and more accurately termed the conterminous, coterminous or contiguous United States
- Alaska, which is physically connected only to Canada
- the archipelago of Hawaii, in the central Pacific Ocean. The United States also holds several other territories, districts, and possessions, notably the federal district of the District of Columbia, which is the nation's capital, and several overseas insular areas, the most significant of which are American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Palmyra Atoll is the United States' only incorporated territory; it is unorganized and uninhabited. The United States Navy has held a base at a portion of Guantanamo Bay, Cuba, since 1898. The United States government possesses a lease to this land, which only mutual agreement or United States abandonment of the area can terminate. The present Cuban government of Fidel Castro disputes this arrangement, claiming Cuba was not truly sovereign at the time of the signing. The United States argues this point moot because Cuba apparently ratified the lease post-revolution, and with full sovereignty, when it cashed one rent check in accordance with the disputed treaty.

Foreign relations and military

sovereign] The immense military and economic dominance of the United States has made foreign relations an especially important topic in its politics, with considerable concern about the image of the United States throughout the world. Reactions towards the United States by other nationalities are often strong, ranging from uninhibited admiration and mimicking of all things American to anti-Americanism. US foreign policy has swung about several times over the course of its history between the poles of strict isolationism and imperialism and everywhere in between. Three of the nation's four military branches are administered by the Department of Defense: the Army, the Navy (including the Marine Corps), and the Air Force. The Coast Guard falls under the jurisdiction of the Department of Homeland Security in peacetime, but is placed under the Department of the Navy in time of war. The combined United States armed forces consist of 1.4 million active duty personnel, along with several hundred thousand each in the Reserves and the National Guard. Military conscription ended in 1973. The United States Armed forces are considered to be the most powerful military (of any sort) on Earth and their force projection capabilities are unrivaled by any other nation. The 2005 defense budget amounted to $401.7 billion, which is an increase of 4% over 2004 and of 35% since 2001. Over 50% of that number is spent in research & development. (For comparison, in 2004 the European Union (considered as the second-largest military force) had a combined total of 1.6 million troops, and a defense budget of €160 billion, with less than 10% of that being spent on R&D.)

Largest cities

The United States has dozens of major cities, including 11 of the 55 global cities of all types — with three "alpha" global cities: New York City, Los Angeles, and Chicago. The figures expressed below are for populations within city limits. A different ranking is evident when considering U.S. metro area populations, although the top three would be unchanged. Note that some cities not listed (such as Atlanta, Boston, Las Vegas, Miami, Nashville, New Orleans, Seattle, and Washington, D.C.) are still considered important on the basis of other factors and issues, including culture, economics, heritage, and politics. The twenty largest cities, based on the United States Census Bureau's 2004 estimates, are as follows:

Economy

The United States has the largest single-country economy in the world, with a per-capita gross domestic product of $40,100. In this market-oriented economy, private individuals and business firms make most of the decisions, and the federal and state governments buy needed goods and services predominantly in the private marketplace. gross domestic product The largest industry of the U.S. is now service, which employs roughly three quarters of the U.S. work force. The United States has many natural resources, including oil and gas, metals, and such minerals as gold, soda ash, and zinc. In agriculture, the U.S. is a top producer of, among other crops, corn, soy beans, and wheat; the United States is a net exporter of food. The U.S. manufacturing sector produces goods such as, cars, airplanes, steel, and electronics, among many others. Economic activity varies greatly from one part of the country to another, with many industries being largely dependent on a certain city or region; New York City is the center of the American financial, publishing, broadcasting, and advertising industries; Silicon Valley is the country’s primary location for high-technology companies, while Los Angeles is the most important center for film production. The Midwest is known for its reliance on manufacturing and heavy industry, with Detroit, Michigan, serving as the center of the American automotive industry; the Great Plains are known as the "breadbasket" of America for their tremendous agricultural output; the intermountain region serves as a mining hub and natural gas resource; the Pacific Northwest for fish and timber, while Texas is largely associated with the oil industry; the Southeast is a major hub for both medical research and the textiles industry. Several countries continue to link their currency to the dollar or even use it as a currency (such as Ecuador), although this practice has subsided since the collapse of the Bretton Woods system. Many markets are also quoted in dollars, such as those of oil and gold. The dollar is also the predominant reserve currency in the world, and more than half of global reserves are in dollars. The largest trading partner of the United States is Canada (19%), followed by China (12%), Mexico (11%), and Japan (8%). More than 50% of total trade is with these four countries. In 2003, the United States was ranked as the third most visited tourist destination in the world; its 40,400,000 visitors ranked behind France's 75,000,000 and Spain's 52,500,000. Labor unions have existed since the 19th century, and grew large and powerful from the 1930s to the 1950s. See Labor history of the United States. Since 1970 they have shrunk in the private sector and now cover fewer than 8% of the workers. However union membership has grown rapidly in the public sector, especially among teachers, nurses, police, postal workers, and municipal clerks. There have been few strikes in recent years. The United States' imports exceed exports by 80%, leading to an annual trade deficit of $700,000,000,000, or 6% of gross domestic product. It is the largest debtor nation in the world, with total gross foreign debt of over $13,000,000,000,000 (2005 estimate); and it absorbs more than 50% of global savings annually. Since the 1980s, the U.S. has increased the use of neoliberal economic policies that reduce government intervention and reduce the size of the welfare state, backing away from the more interventionist Keynsian economic policies that had been in favor since the Great Depression. As a result, the United States provides fewer government-delivered social welfare services than most industrialized nations, choosing instead to keep its tax burden lower and relying more heavily on the free market and private charities. Sixteen states and the District of Columbia have minimum wages higher than the national level ($5.15 per-hour), including the highest, Washington State at $7.35. Twenty-six states are the same as the federal level; two--Ohio and Kansas--are below; and six do not have state laws. America's wealth is relatively highly concentrated. The average C.E.O. earns 500 times the typical amount a worker grosses, this is up from 25 times in the late 1970s. In terms of wealth the top 1% of Americans own 40% of all assets and 50.1% of the country's income goes to the top twenty percent of households. Average wages for the majority of employees have been largely stagnating since the 1970s. America's poverty line defined as a family of four earning less than $19,157 is at 12.7% of the general population. Approximately one out of every five children in the United States grows up below the official poverty line. Among racial groups; African Americans have the lowest median income while Asians had the highest. Regionally, the southern states had the lowest median incomes while the West Coast and New England had the highest. The current Federal Reserve Chairman Alan Greenspan remarked that the U.S.’s growing income inequality since the 1970s is, "not the type of thing which a democratic society - a capitalist democratic society - can really accept without addressing."[http://www.csmonitor.com/2005/0614/p01s03-usec.html?s=itm] However, Greenspan also noted, "...you can look at the system and say it's got a lot of problems to it, and sure it does. It always has. But you can't get around the fact that this is the most extraordinarily successful economy in history."

Transportation

Alan Greenspan ]] Because the United States is a relatively young nation, most of the development of U.S. cities has taken place since the invention of the automobile. To link its vast territory, the United States built a network of high-capacity, high-speed highways, of which the most important element is the Interstate Highway system, commissioned in the 1950s by President Dwight D. Eisenhower and modeled after the German Autobahn. The United States also has a transcontinental rail system, which is used for moving freight across the lower forty-eight states. Passenger rail service is provided by Amtrak, which serves forty-six of the lower forty-eight states. Many cities in the United States have extensive mass-transit systems. New York City operates one of the world's largest and most heavily used subway systems. The regional rail and bus networks that extend into Long Island, New Jersey, Upstate New York, and Connecticut are among the most heavily used in the world. Air travel is often preferred for destinations over 300 miles (500 kilometers) away. In terms of passengers, seventeen of the world's thirty busiest airports in 2004 were in the U.S., including the world's busiest, Hartsfield-Jackson Atlanta International Airport; in terms of cargo, in the same year, twelve of the world's thirty busiest airports were in the U.S., including the world's busiest, Memphis International Airport. There are several major seaports in the United States; the three busiest are the Port of Los Angeles, California; the Port of Long Beach, California; and the Port of New York and New Jersey. Others include Houston, Texas; Charleston, South Carolina; Savannah, Georgia; Miami, Florida; Portland, Oregon; San Francisco, California; Boston, Massachusetts; Philadelphia, Pennsylvania; and Seattle, Washington; plus, outside the contiguous forty-eight states, Anchorage, Alaska, and Honolulu, Hawaii.

Society

Demographics

Hawaii The mean center of the U.S. population continues to drift farther west and south. The fastest growing region is the western United States followed by the southern portion. According to Census 2000, the states that saw the greatest increases from 1990 were: Nevada (66.3%), Arizona (40%), Colorado (30.6%), Utah (29.6%), Idaho (28.5%), Georgia (26.4%), Florida (23.5%), Texas (22.8%), North Carolina (21.4%), and Washington (21.1%). [http://www.census.gov/population/cen2000/phc-t2/tab03.pdf]

Ethnicity and race

:Main article: Racial demographics of the United States The United States is a very racially diverse country. According to the 2000 census, it has 31 ethnic groups with at least one million members each, and numerous others represented in smaller amounts. The majority of Americans descend from white European immigrants who arrived at the establishment of the first colonies (most after Reconstruction). This majority--69.1% in 2000--decreases each year, and is expected to become a plurality within a few decades. The most frequently stated European ancestries are German (15.2%), Irish (10.8%), English (8.7%), Italian (5.6%) and Scandinavian (3.7%). Many immigrants also hail from Slavic countries such as Poland and Russia. Other significant immigrant populations came from eastern and southern Europe and French Canada. Russia Hispanics from Mexico and South and Central America are the largest minority group in the country, comprising 12.5% of the population (2000 census). People of Mexican descent made up 7.3% of the population in the 2000 census, and this proportion is expected to increase significantly in the coming decades. About 12.3% (2000 census) of the American people are African Americans (Blacks). African Americans are spread throughout the country, but their presence is largest in the South. Asian Americans--including Native Hawaiians and Pacific Islanders--are a third significant minority (3.7% of the population in 2000). Most Asian Americans are concentrated on the West Coast and Hawaii. The largest groups are immigrants or descendants of emigrants from the Philippines, China, India, Vietnam, South Korea, and Japan. Indigenous peoples in the United States, such as American Indians and Inuit, make up 0.9% of the population (2000 census). About 35% live on Indian reservations.

Religion

Polls estimate that just under 80 percent of Americans are Christians of various denominations. The other 20 percent comprises other religions such as Hinduism, Judaism, Islam, and Buddhism, other various faiths, and those without a specific religion. The United States is noteworthy among developed nations for its relatively high level of religiosity. According to a 2004 Gallup poll, about 44% of Americans attend a religious service at least once a week. However, this rate is not uniform across the country; attendance is more common in the Bible Belt—composed largely of Southern and Midwestern states—than in the Northeast and West Coast. In the Southern states, Baptists are the largest group, followed by Methodists; Roman Catholics are dominant in the Northeast and in large parts of the Midwest due to their being settled by descendants of Catholic immigrants from Europe (such as Germany, Ireland, Italy, and Poland) or other parts of North America (mainly Quebec and Puerto Rico). The rest of the country for the most part has a complex mixture of various Christian groups.

Education

West Coast's home at Monticello and the University of Virginia (library building shown above, and designed by Jefferson), the only collegiate campus on the list. Both sites are located in Charlottesville, Virginia.]] In the United States, education is a state, not federal, responsibility, and the laws and standards vary considerably. However, the federal government, through the Department of Education, is involved with funding of some programs and exerts some influence through its ability to control funding. In most states, all students must attend mandatory schooling starting with kindergarten, which children normally enter at age 5, and following through 12th grade, which is normally completed at age 18 (although

Columnist

A columnist is a journalist who produces a specific form of writing for publication called a "column". Columns appear in newspapers, magazines and the Internet. Some Internet columns are called blogs or Weblogs. What differentiates a column from other forms of journalism is that it meets each of the following criteria:
- It is a regular feature in a publication
- It is personality-driven by the author
- It contains an opinion or point of view

Types of columns


- advice
- critic reviews
- editorial opinion
- gossip
- humor

Columnists of note


- Shana Alexander
- Barbara Amiel
- Army Archerd
- Mike Barnicle (Boston Herald, USA)
- Dave Barry (Miami Herald, USA)
- Christie Blatchford (The Globe and Mail, Canada)
- David Brooks (New York Times, USA)
- Ann Coulter (Universal Press Syndicate, USA)
- Andrew Coyne
- Maureen Dowd (New York Times, USA)
- John Doyle (The Globe and Mail, Canada)
- Matt Drudge
- Gwynne Dyer
- Roger Ebert
- Allan Fotheringham
- Benjamin Franklin
- Thomas Friedman (New York Times, USA)
- David Frum
- Robert Fulford (National Post, Canada)
- Carl Hiaasen (Miami Herald, USA)
- Simon Heffer, UK
- Peter Hitchens, UK
- Molly Ivins
- Michael Kinsley
- Charles Krauthammer (Washington Post, USA)
- Paul Krugman (New York Times, USA)
- Ann Landers
- Michele Landsberg (Toronto Star)
- Richard Littlejohn (The Sun and Daily Mail, UK)
- Charlie Madigan (Chicago Tribune, USA)
- Michelle Malkin
- Heather Mallick (The Globe and Mail, Canada)
- Dan Margalit
- Vinod Mehta
- Ward Morehouse III www.wardmorehouseiii.com
- Rex Murphy
- Al Neuharth
- Peter C. Newman
- Robert Novak
- Clarence Page (Chicago Tribune, USA)
- Adam J. Pearce, UK
- Daniel Pipes
- Dennis Prager
- Will Rogers
- Amnon Rubinstein (Maariv, Israel)
- William Safire (New York Times, USA)
- Mary Schmich (Chicago Tribune, USA)
- Jeffrey Simpson
- Thomas Sowell
- Mark Steel
- Mark Steyn
- Andrew Sullivan
- Ellie Tesher
- Cal Thomas
- Polly Toynbee
- Mark Twain
- George Will
- Fareed Zakaria

External links


- [http://www.journaliststoolbox.com/newswriting/columnists.html American Press Institute columnist tool box] Category:Opinion journalism

Computer

A computer is a device capable of processing data according to a program — a list of instructions. The data to be processed may represent many types of information including numbers, text, pictures, or sound. Computers can be extremely versatile. In fact, they are universal information processing machines. According to the Church-Turing thesis, a computer with a certain minimum threshold capability is in principle capable of performing the tasks of any other computer, from those of a personal digital assistant to a supercomputer. Therefore, the same computer designs have been adapted for tasks from processing company payrolls to controlling industrial robots. Modern electronic computers also have enormous speed and capacity for information processing compared to earlier designs, and they have become exponentially more powerful over the years (a phenomenon known as Moore's Law). Computers are available in many physical forms. The original computers were the size of a large room, and such enormous computing facilities still exist for specialized scientific computation - supercomputers - and for the transaction processing requirements of large companies, generally called mainframes. Smaller computers for individual use, called personal computers, and their portable equivalent, the notebook computer, are ubiquitous information-processing and communication tools and are perhaps what most non-experts think of as "a computer". However, the most common form of computer in use today is the embedded computer, small computers used to control another device. Embedded computers control machines from fighter planes to digital cameras.

History of computing

Originally, a "computer" was a person who performed numerical calculations under the direction of a mathematician, often with the aid of a variety of mechanical calculating devices from the abacus onward. An example of an early computing device was the Antikythera mechanism, an ancient Greek device for calculating the movements of planets, dating from about 87 BCE. The technology responsible for this mysterious device seems to have been lost at some point. The end of the Middle Ages saw a reinvigoration of European mathematics and engineering, and by the early 17th century a succession of mechanical calculating devices had been constructed using clockwork technology. A considerable number of technologies that would later prove vital for the digital computer were developed in the late 19th and early 20th centuries, such as the punched card and the vacuum tube ((or valve). Charles Babbage was the first to conceptualize and design a fully programmable computer as early as 1837, but due to a combination of the limits of the technology of the time, limited finance, and an inability to resist tinkering with his design (a trait that would in time doom thousands of computer-related engineering projects), the device was never actually constructed in his lifetime. During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated, special-purpose analog computers, which used a direct physical or electrical model of the problem as a basis for computation. These became increasingly rare after the development of the digital computer. A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features of modern computers, such as the use of digital electronics (invented by Claude Shannon in 1937) and more flexible programmability. Defining one point along this road as "the first computer" is exceedingly difficult. Notable achievements include the Atanasoff Berry Computer, a special-purpose machine that used valve-driven computation and binary numbers; Konrad Zuse's Z machines; the secret British Colossus computer, which had limited programmability but demonstrated that a device using thousands of valves could be made reliable and reprogrammed electronically; and the American ENIAC — the first general purpose machine, but with an inflexible architecture that meant reprogramming it essentially required it to be rewired. The team who developed ENIAC, recognizing its flaws, came up with a far more flexible and elegant design, which has become known as the stored program architecture, which is the basis from which virtually all modern computers were derived. A number of projects to develop computers based on the stored program architecture commenced in the late 1940s; the first of these to be up and running was the Small-Scale Experimental Machine, but the EDSAC was perhaps the first practical version. Valve-driven computer designs were in use throughout the 1950s, but were eventually replaced with transistor-based computers, which were smaller, faster, cheaper, and much more reliable, thus allowing them to be commercially produced, in the 1960s. By the 1970s, the adoption of integrated circuit technology had enabled computers to be produced at a low enough cost to allow individuals to own a personal computer of the type familiar today.

How computers work: the stored program architecture

While the technologies used in computers have changed dramatically since the first electronic, general-purpose, computers of the 1940s, most still use the stored program architecture (sometimes called the von Neumann architecture; as the article describes the primary inventors were probably ENIAC designers J. Presper Eckert and John William Mauchly). The design made the universal computer a practical reality. The architecture describes a computer with four main sections: the arithmetic and logic unit (ALU), the control circuitry, the memory, and the input and output devices (collectively termed I/O). These parts are interconnected by a bundle of wires (a "bus") and are usually driven by a timer or clock (although other events could drive the control circuitry). Conceptually, a computer's memory can be viewed as a list of cells. Each cell has a numbered "address" and can store a small, fixed amount of information. This information can either be an instruction, telling the computer what to do, or data, the information which the computer is to process using the instructions that have been placed in the memory. In principle, any cell can be used to store either instructions or data. The ALU is in many senses the heart of the computer. It is capable of performing two classes of basic operations: arithmetic operations, the core of which is the ability to add or subtract two numbers but also encompasses operations like "multiply this number by 2" or "divide by 2" (for reasons which will become clear later), as well as some others. The second class of ALU operations involves comparison operations, which, given two numbers, can determine if they are equal, and if not, which is bigger. The I/O systems are the means by which the computer receives information from the outside world, and reports its results back to that world. On a typical personal computer, input devices include objects like the keyboard and mouse, and output devices include computer monitors, printers and the like, but as will be discussed later a huge variety of devices can be connected to a computer and serve as I/O devices. The control system ties this all together. Its job is to read instructions and data from memory or the I/O devices, decode the instructions, providing the ALU with the correct inputs according to the instructions, "tell" the ALU what operation to perform on those inputs, and send the results back to the memory or to the I/O devices. One key component of the control system is a counter that keeps track of what the address of the current instruction is; typically, this is incremented each time an instruction is executed, unless the instruction itself indicates that the next instruction should be at some other location (allowing the computer to repeatedly execute the same instructions). Physically, since the 1980s the ALU and control unit have been located on a single integrated circuit called a Central Processing Unit or CPU. The functioning of such a computer is in principle quite straightforward. Typically, on each clock cycle, the computer fetches instructions and data from its memory. The instructions are executed, the results are stored, and the next instruction is fetched. This procedure repeats until a halt instruction is encountered. Larger computers, such as some minicomputers, mainframe computers, servers, differ from the model above in one significant aspect; rather than one CPU they often have a number of them. Supercomputers often have highly unusual architectures significantly different from the basic stored-program architecture, sometimes featuring thousands of CPUs, but such designs tend to be useful only for specialized tasks.

Digital circuits

The conceptual design above could be implemented using a variety of different technologies. As previously mentioned, a stored program computer could be designed entirely of mechanical components like Babbage's. However, digital circuits allow Boolean logic and arithmetic using binary numerals to be implemented using relays - essentially, electrically controlled switches. Shannon's famous thesis showed how relays could be arranged to form units called logic gates, implementing simple Boolean operations. Others soon figured out that vacuum tubes - electronic devices, could be used instead. Vacuum tubes were originally used as a signal amplifier for radio and other applications, but were used in digital electronics as a very fast switch; when electricity is provided to one of the pins, current can flow through between the other two. Through arrangements of logic gates, one can build digital circuits to do more complex tasks, for instance, an adder, which implements in electronics the same method - in computer terminology, an algorithm - to add two numbers together that children are taught - add one column at a time, and carry what's left over. Eventually, through combining circuits together, a complete ALU and control system can be built up. This does require a considerable number of components. CSIRAC, one of the earliest stored-program computers, is probably close to the smallest practically useful design. It had about 2,000 valves, some of which were "dual components", so this represented somewhere between 2 and 4,000 logic components. Vacuum tubes had severe limitations for the construction of large numbers of gates. They were expensive, unreliable (particularly when used in such large quantities), took up a lot of space, and used a lot of electrical power, and, while incredibly fast compared to a mechanical switch, had limits to the speed at which they could operate. Therefore, by the 1960s they were replaced by the transistor, a new device which performed the same task as the tube but was much smaller, faster operating, reliable, used much less power, and was far cheaper. transistor In the 1960s and 1970s, the transistor itself was gradually replaced by the integrated circuit, which placed multiple transistors (and other components) and the wires connecting them on a single, solid piece of silicon. By the 1970s, the entire ALU and control unit, the combination becoming known as a CPU, were being placed on a single "chip" called a microprocessor. Over the history of the integrated circuit, the number of components that can be placed on one has grown enormously. The first IC's contained a few tens of components; as of 2005, modern microprocessors such from AMD and Intel contain over 100 million transistors. Tubes, transistors, and transistors on integrated circuits can be and are used as the "storage" component of the stored-program architecture, using a circuit design known as a flip-flop, and indeed flip-flops are used for small amounts of very high-speed storage. However, few computer designs have used flip-flops for the bulk of their storage needs. Instead, earliest computers stored data in Williams tubes - essentially, projecting some dots on a TV screen and reading them again, or mercury delay lines where the data was stored as sound pulses traveling slowly (compared to the machine itself) along long tubes filled with mercury. These somewhat ungainly but effective methods were eventually replaced by magnetic memory devices, such as magnetic core memory, where electrical currents were used to introduce a permanent (but weak) magnetic field in some ferrous material, which could then be read to retrieve the data. Eventually, DRAM was introduced. A DRAM unit is a type of integrated circuit containing huge banks of an electronic component called a capacitor which can store an electrical charge for a period of time. The level of charge in a capacitor could be set to store information, and then measured to read the information when required.

I/O devices

I/O is a general term for devices that send computers information from the outside world and that return the results of computations. These results can either be viewed directly by a user, or they can be sent to another machine, whose control has been assigned the computer: In a robot, for instance, the controlling computer's major output device is the robot itself. The first generation of computers were equipped with a fairly limited range of input devices. A punch card reader, or something similar, was used to enter instructions and data into the computer's memory, and some kind of printer, usually a modified teletype, was used to record the results. Over the years, a huge variety of other devices have been added. For the personal computer, for instance, keyboards and mice are the primary ways people directly enter information into the computer; and monitors are the primary way in which information from the computer is presented back to the user, though printers, speakers, and headphones are common, too. There is a huge variety of other devices for obtaining other types of input. One example is the digital camera, which can be used to input visual information. There are two prominent classes of I/O devices. The first class is that of secondary storage devices, such as hard disks, CD-ROMs, key drives and the like, which represent comparatively slow, but high-capacity devices, where information can be stored for later retrieval; the second class is that of devices used to access computer networks. The ability to transfer data between computers has opened up a huge range of capabilities for the computer. The global Internet allows millions of computers to transfer information of all types between each other.

Instructions

The instructions interpreted by the control unit, and executed by the ALU, are not nearly as rich as a human language. A computer responds only to a limited number of instructions, but they are well defined, simple, and unambiguous. Typical sorts of instructions supported by most computers are "copy the contents of memory cell 5 and place the copy in cell 10", "add the contents of cell 7 to the contents of cell 13 and place the result in cell 20", "if the contents of cell 999 are 0, the next instruction is at cell 30". All computer instructions fall into one of four categories: 1) moving data from one location to another; 2) executing arithmetic and logical processes on data; 3) testing the condition of data; and 4) altering the sequence of operations. Instructions are represented within the computer as binary code - a base two system of counting. For example, the code for one kind of "copy" operation in the Intel line of microprocessors is 10110000. The particular instruction set that a specific computer supports is known as that computer's machine language. To slightly oversimplify, if two computers have CPUs that respond to the same set of instructions identically, software from one can run on the other without modification. This easy portability of existing software creates a great incentive to stick with existing designs, only switching for the most compelling of reasons, and has gradually narrowed the number of distinct instruction set architectures in the marketplace.

Programs

Computer programs are simply lists of instructions for the computer to execute. These can range from just a few instructions which perform a simple task, to a much more complex instruction list which may also include tables of data. Many computer programs contain millions of instructions, and many of those instructions are executed repeatedly. A typical modern PC (in the year 2005) can execute around 3 billion instructions per second. Computers do not gain their extraordinary capabilities through the ability to execute complex instructions. Rather, they do millions of simple instructions arranged by people known as programmers. In practice, people do not normally write the instructions for computers directly in machine language. Such programming is incredibly tedious and highly error-prone, making programmers very unproductive. Instead, programmers describe the desired actions in a "high level" programming language which is then translated into the machine language automatically by special computer programs (interpreters and compilers). Some programming languages map very closely to the machine language, such as Assembly Language (low level languages); at the other end, languages like Prolog are based on abstract principles far removed from the details of the machine's actual operation (high level languages). The language chosen for a particular task depends on the nature of the task, the skill set of the programmers, tool availability and, often, the requirements of the customers (for instance, projects for the US military were often required to be in the Ada programming language). Computer software is an alternative term for computer programs; it is a more inclusive phrase and includes all the ancillary material accompanying the program needed to do useful tasks. For instance, a video game includes not only the program itself, but also data representing the pictures, sounds, and other material needed to create the virtual environment of the game. A computer application is a piece of computer software provided to many computer users, often in a retail environment. The stereotypical modern example of an application is perhaps the office suite, a set of interrelated programs for performing common office tasks. Going from the extremely simple capabilities of a single machine language instruction to the myriad capabilities of application programs means that many computer programs are extremely large and complex. A typical example is the Firefox web browser, created from roughly 2 million lines of computer code in the C++ programming language; there are many projects of even bigger scope, built by large teams of programmers. The management of this enormous complexity is key to making such projects possible; programming languages, and programming practices, enable the task to be divided into smaller and smaller subtasks until they come within the capabilities of a single programmer in a reasonable period. Nevertheless, the process of developing software remains slow, unpredictable, and error-prone; the discipline of software engineering has attempted, with some partial success, to make the process quicker and more productive and improve the quality of the end product.

Libraries and operating systems

Soon after the development of the computer, it was discovered that certain tasks were required in many different programs; an early example was computing some of the standard mathematical functions. For the purposes of efficiency, standard versions of these were collected in libraries and made available to all who required them. A particularly common task set related to handling the gritty details of "talking" to the various I/O devices, so libraries for these were quickly developed. By the 1960s, with computers in wide industrial use for many purposes, it became common for them to be used for many different jobs within an organization. Soon, special software to automate the scheduling and execution of these many jobs became available. The combination of managing "hardware" and scheduling jobs became known as the "operating system"; the classic example of this type of early operating system was OS/360 by IBM. The next major development in operating systems was timesharing - the idea that multiple users could use the machine "simultaneously" by keeping all of their programs in memory, executing each user's program for a short time so as to provide the illusion that each user had their own computer. Such a development required the operating system to provide each user's programs with a "virtual machine" such that one user's program could not interfere with another's (by accident or design). The range of devices that operating systems had to manage also expanded; a notable one was hard disks; the idea of individual "files" and a hierarchical structure of "directories" (now often called folders) greatly simplified the use of these devices for permanent storage. Security access controls, allowing computer users access only to files, directories and programs they had permissions to use, were also common. Perhaps the last major addition to the operating system were tools to provide programs with a standardized graphical user interface. While there are few technical reasons why a GUI has to be tied to the rest of an operating system, it allows the operating system vendor to encourage all the software for their operating system to have a similar looking and acting interface. Outside these "core" functions, operating systems are usually shipped with an array of other tools, some of which may have little connection with these original core functions but have been found useful by enough customers for a provider to include them. For instance, Apple's Mac OS X ships with a digital video editor application. Not all operating systems provide all of the above functions; operating systems for smaller computers typically provide fewer, such as the highly minimal operating systems for early microcomputers. Embedded computers may have a specialized operating system, or sometimes none at all. Instead, the custom programs written for their task perform all necessary functions that would be performed by an operating system in less specialized roles.

Computer applications

Embedded computer The first electronic digital computers, with their large size and cost, mainly performed scientific calculations, often to support military objectives. The ENIAC was originally designed to calculate ballistics-firing tables for artillery, but it was also used to calculate neutron cross-sectional densities to help in the design of the