History.

International conflicts.

Various international conflicts motivated the creation of an agreement for the Antarctic. After the Second World War, the U.S. considered establishing a claim in Antarctica. From August 26, 1946, and until the beginning of 1947, Operation Highjump was carried out, the largest military expeditionary force that the United States has sent to Antarctica to the present, consisting of 13 ships, 4700 men and numerous aerial devices. Its goals were to train military personnel and test material in conditions of extreme cold for an eventual war in the Antarctic.  Some incidents had occurred during World War II, and a new one occurred in Hope Bay on February 1, 1952, when the Argentine military fired warning shots at a group of Britons. The response of the United Kingdom was to send a warship that landed marines on February 4, at the scene. This occurred; however, after 1949, Argentina, Chile, and the United Kingdom signed a Tripartite Naval Declaration committing not to send warships south of the 60th South parallel, which was renewed annually until 1961 when it was deemed unnecessary when the treaty entered into force. This tripartite declaration was signed after the tension generated when Argentina sent to Antarctica in February 1948 a fleet of 8 warships.  On January 17, 1953, Argentina reopened the Lieutenant Lasala refuge on Deception Island, leaving a sergeant and a corporal in the Argentine Navy. On February 15, in the incident on Deception Island, 32 royal marines landed from the British frigate HMS Snipe armed with Sten machine guns, rifles, and tear gas capturing the two Argentine sailors. The Argentine refuge and a nearby uninhabited Chilean shelter were destroyed, and the Argentine sailors were delivered to a ship from that country on February 18 in the South Georgias Islands. A British detachment remained three months on the island while the frigate patrolled its waters until April.  On May 4, 1955, the United Kingdom filed two lawsuits, against Argentina and Chile respectively, before the International Court of Justice to declare the invalidity of the claims of the sovereignty of the two countries over Antarctic and sub-Antarctic areas. On July 15, 1955, the Chilean Government rejected the jurisdiction of the Court in that case, and on August 1, the Argentine Government also did so, so on March 16, 1956, the claims were filed.

Previous agreements.

On September 2, 1947, the American quadrant of Antarctica (between 24 ° W and 90 ° W) was included as part of the security zone of the Inter-American Treaty of Reciprocal Assistance, committing its members to defend it in case of external aggression.  In August 1948, the United States proposed that Antarctica be under the guardianship of the United Nations as a trust administered by Argentina, Australia, Chile, France, United States, United Kingdom, and New Zealand. Still, the idea was rejected by Argentina, Australia, Chile, France, and Norway. Before the rejection, on August 28, 1948, the United States proposed to the claimants some form of internationalization of Antarctica, with the support of the United Kingdom. Chile responded by presenting a plan to suspend any Antarctic claim for 5 to 10 years while negotiating a final solution, which did not prosper. The interest of the United States to keep the Soviet Union away from Antarctica was frustrated when in 1950, this country informed the claimants that it would not accept any Antarctic agreement in which it was not represented. The fear that the USSR would react by doing a territorial claim transferring the Cold War to Antarctica led the United States to do none. In 1956 and 1958, India tried unsuccessfully to bring the Antarctic issue to the United Nations General Assembly.

International Geophysical Year.

In 1950 the International Council of Scientific Unions (ICSU) discussed the possibility of holding a third International Polar Year. At the suggestion of the World Meteorological Organization, the idea of the International Polar Year was extended to the entire planet, thus creating the International Geophysical Year that took place between July 1, 1957, and December 31, 1958. In this event, 66 countries participated. At the ICSU meeting in Stockholm from September 9 to 11, 1957, the creation of a Special Committee for Antarctic Research (SCAR) was approved, inviting the twelve countries conducting Antarctic investigations to send delegates to integrate the committee, with the purpose of exchanging scientific information among its members regarding Antarctica. The SCAR was later renamed to the Scientific Committee for Research in Antarctica.  Both Argentina and Chile expressed that researching during the International Geophysical Year would not give any territorial rights to the participants and that the facilities that were erected during that year should then be dismantled at the end of it. After the United States proposed to extend the Antarctic investigations for another year, in February 1958, the Soviet Union reported that it would maintain its scientific bases until the studies that were carried out were completed.

Negotiation of the treaty.

Scientific bases increased in international tension concerning Antarctica, and the danger of the Cold War spreading to that continent, caused the President of the United States, Dwight D. Eisenhower, to convene an Antarctic Conference to the twelve countries active in Antarctica during the International Geophysical Year, to sign a treaty. In the first phase, representatives of the twelve nations met in Washington, who met in 60 sessions from June 1958 to October 1959, to define the basic negotiating framework. Still, no consensus was reached on a preliminary draft. In the second phase, a conference of the highest diplomatic level was held from October 15 to December 1, 1959, the date of the signing of the treaty. The central ideas with full acceptance were the freedom of scientific research in Antarctica and the peaceful use of the continent. Still, their demilitarization and the maintenance of the "status quo" also had consensus.  The positions of the United States, the Soviet Union, the United Kingdom, and New Zealand coincided in the establishment of an international administration for Antarctica, proposing the latter to be within the framework of the United Nations. Australia and the United Kingdom expressed the need for inspections by observers, and the second proposed the use of military means for logistics functions. Argentina proposed that all atomic explosions be banned in Antarctica, which caused a crisis that lasted until the eve of the firm, since the United States, along with other countries, intended to ban only those that were made without prior notice and without prior consultation. The support of the USSR and Chile to the Argentine proposal finally caused the United States to retract its opposition.  The signing of the treaty was the first arms control agreement that occurred in the framework of the Cold War, and the complaining countries managed to avoid the internationalization of Antarctic sovereignty.

Articles of the Antarctic Treaty.

Article VI.

The provisions of the present treaty shall apply to the area south of 60-degree South Latitude, including all ice shelves, but nothing in the present treaty shall prejudice or in any way affect the rights, or the exercise of the rights, of any State under international law with regard to the high seas within that area.

Articles XII, XIII, XIV.

The main objective of the ATS is to ensure in the interests of all humankind that Antarctica shall continue forever to be used exclusively for peaceful purposes and shall not become the scene or object of international discord. Pursuant to Article 1, the treaty forbids any measures of a military nature, but not the presence of military personnel or equipment for the purposes of scientific research.

Other agreements.

Other agreements — some 200 recommendations adopted at treaty consultative meetings and ratified by governments — include:

Meetings.

The Antarctic Treaty System's yearly "Antarctic Treaty Consultative Meetings (ATCM)" are the international forum for the administration and management of the region. Only 29 of the 54 parties to the agreements have the right to participate in decision-making at these meetings, though the other 25 are still allowed to attend. The decision-making participants are the "Consultative Parties" and, in addition to the 12 original signatories, include 17 countries that have demonstrated their interest in Antarctica by carrying out substantial scientific activity there. The Antarctic Treaty also has "Special Antarctic Treaty Consultative Meetings (SATCM)", which are generally summoned to treat more important topics but are less frequents and Meetings of Experts.

Parties.

As of 2019, there are 54 states party to the treaty, 29 of which, including all 12 original signatories to the treaty, have consultative (voting) status. Consultative members include the seven nations that claim portions of Antarctica as national territory. The 46 non-claimant nations either do not recognize the claims of others, or have not stated their positions. 40 parties to the Antarctic Treaty have also ratified the "Protocol on Environmental Protection to the Antarctic Treaty".

Antarctic Treaty Secretariat.

The "Antarctic Treaty Secretariat" was established in Buenos Aires, Argentina in September 2004 by the Antarctic Treaty Consultative Meeting (ATCM). Jan Huber (Netherlands) served as the first Executive Secretary for five years until August 31, 2009. He was succeeded on September 1, 2009, by Manfred Reinke (Germany).  The tasks of the Antarctic Treaty Secretariat can be divided into the following areas:

Legal system.

Antarctica currently has no permanent population and therefore it has no citizenship nor government. Personnel present on Antarctica at any time are almost always citizens or nationals of some sovereignty outside Antarctica, as there is no Antarctic sovereignty. The majority of Antarctica is claimed by one or more countries, but most countries do not explicitly recognize those claims. The area on the mainland between 90 degrees west and 150 degrees west is the only major land on Earth not claimed by any country. Until 2015 the interior of the Norwegian Sector, the extent of which had never been officially defined, was considered to be unclaimed. That year, Norway formally laid claim to the area between its Queen Maud Land and the South Pole.  Governments that are party to the Antarctic Treaty and its Protocol on Environmental Protection implement the articles of these agreements, and decisions taken under them, through national laws. These laws generally apply only to their own citizens, wherever they are in Antarctica, and serve to enforce the consensus decisions of the consultative parties: about which activities are acceptable, which areas require permits to enter, what processes of environmental impact assessment must precede activities, and so on. The Antarctic Treaty is often considered to represent an example of the common heritage of mankind principle.

Australia.

Since the designation of the Australian Antarctic Territory pre-dated the signing of the Antarctic Treaty, Australian laws that relate to Antarctica date from more than two decades before the Antarctic Treaty era. In terms of criminal law, the laws that apply to the Jervis Bay Territory (which follows the laws of the Australian Capital Territory) apply to the Australian Antarctic Territory. Key Australian legislation applying Antarctic Treaty System decisions include the "Antarctic Treaty Act 1960", the "Antarctic Treaty (Environment Protection) Act 1980" and the "Antarctic Marine Living Resources Conservation Act 1981".

United States.

The law of the United States, including certain criminal offences by or against U.S. nationals, such as murder, may apply to areas not under jurisdiction of other countries. To this end, the United States now stations special deputy U.S. Marshals in Antarctica to provide a law enforcement presence.  Some U.S. laws directly apply to Antarctica. For example, the Antarctic Conservation Act, Public Law 95-541, "et seq.", provides civil and criminal penalties for the following activities, unless authorized by regulation or statute:  Violation of the Antarctic Conservation Act carries penalties of up to US$10,000 in fines and one year in prison. The Departments of the Treasury, Commerce, Transportation, and the Interior share enforcement responsibilities. The Act requires expeditions from the U.S. to Antarctica to notify, in advance, the Office of Oceans and Polar Affairs of the State Department, which reports such plans to other nations as required by the Antarctic Treaty. Further information is provided by the Office of Polar Programs of the National Science Foundation.

New Zealand.

In 2006, the New Zealand police reported that jurisdictional issues prevented them issuing warrants for potential American witnesses who were reluctant to testify during the Christchurch Coroner's investigation into the death by poisoning of Australian astrophysicist Rodney Marks at the South Pole base in May 2000. Dr. Marks died while wintering over at the United States' Amundsen–Scott South Pole Station located at the geographic South Pole. Prior to autopsy, the death was attributed to natural causes by the National Science Foundation and the contractor administering the base. However, an autopsy in New Zealand revealed that Dr. Marks died from methanol poisoning. The New Zealand Police launched an investigation. In 2006, frustrated by lack of progress, the Christchurch Coroner said that it was unlikely that Dr. Marks ingested the methanol knowingly, although there is no certainty that he died as the direct result of the act of another person. During media interviews, the police detective in charge of the investigation criticized the National Science Foundation and contractor Raytheon for failing to co-operate with the investigation.

South Africa.

South African law applies to all South African citizens in Antarctica, and they are subject to the jurisdiction of the magistrate's court in Cape Town. In regard to violations of the Antarctic Treaty and related agreements, South Africa also asserts jurisdiction over South African residents and members of expeditions organised in South Africa.

The Antarctic Treaty and related agreements, collectively known as the Antarctic Treaty System (ATS), regulate international relations with respect to Antarctica, Earth's only continent without a native human population. For the purposes of the treaty system, Antarctica is defined as all of the land and ice shelves south of 60°S latitude. The treaty entered into force in 1961 and currently has 54 parties. The treaty sets aside Antarctica as a scientific preserve, establishes freedom of scientific investigation, and bans military activity on the continent. The treaty was the first arms control agreement established during the Cold War. Since September 2004, the Antarctic Treaty Secretariat headquarters has been located in Buenos Aires, Argentina.

Antarktický smluvní systém () je komplex opatření regulující vztahy mezi jednotlivými státy v oblasti Antarktidy. Pro účely ATS je Antarktida definována jako území jižně od 60. rovnoběžky včetně plovoucích ledovců.


Definition.

The Fourier transform of a function is traditionally denoted formula_1, by adding a circumflex to the symbol of the function. There are several common conventions for defining the Fourier transform of an integrable function formula_2. One of them is  for any real number.  A reason for the negative sign in the exponent is that it is common in electrical engineering to represent by formula_3 a signal with zero initial phase and frequency formula_4 The negative sign convention causes the product formula_5 to be 1 (frequency zero) when formula_6 causing the integral to diverge. The result is a Dirac delta function at formula_7, which is the only frequency component of the sinusoidal signal formula_8  When the independent variable represents "time", the transform variable represents frequency (e.g. if time is measured

History.

In 1822, Joseph Fourier showed that some

Introduction.

One motivation for the Fourier transform comes from the study of Fourier series. In the study of Fourier series, complicated but periodic functions are written as the sum of simple waves mathematically represented by sines and cosines. The Fourier transform is an extension of the Fourier series that results when the period of the represented function is lengthened and allowed to approach infinity.  Due to the properties of sine and cosine, it is possible to recover the amplitude of each wave in a Fourier series using an integral. In many cases it is desirable to use Euler's formula, which states that, to write Fourier series in terms of the basic waves. This has the advantage of simplifying many of the formulas involved, and provides a formulation for Fourier series that more closely resembles the definition followed in this article. Re-writing sines and cosines as complex exponentials makes it necessary for the Fourier coefficients to be complex valued. The usual interpretation of this complex number is that it gives both the amplitude (or size) of the wave present in the function and the phase (or the initial angle) of the wave. These complex exponentials sometimes contain negative "frequencies". If is measured in seconds, then the waves and both complete one cycle per second, but they represent different frequencies

Example.

The following figures provide a visual illustration how the Fourier transform measures whether a frequency is present in a particular function. The depicted function oscillates at 3 Hz (if measures seconds) and tends quickly to 0. (The second factor in this equation is an envelope function that shapes the continuous sinusoid into a short pulse. Its general form is a Gaussian function). This function was specially chosen to have a real Fourier transform that can be easily plotted. The first image contains its graph. In order to calculate formula_15 we must integrate. The second image shows the plot of the real and imaginary parts of this function. The real part of

Properties of the Fourier transform.

Here we assume, and are "integrable functions": Lebesgue-measurable on the real line satisfying:  We denote the Fourier transforms of these functions as, and respectively.

Basic properties.

The Fourier transform

Invertibility and periodicity.

Under suitable conditions on the function, it can be recovered from its Fourier transform formula_9. Indeed, denoting the Fourier transform operator by, so, then for suitable functions, applying the Fourier transform twice simply flips the function:, which can be interpreted as "reversing time". Since reversing time is two-periodic, applying this twice yields, so the Fourier transform operator is four-periodic, and similarly the inverse Fourier transform can be obtained by applying the Fourier transform three times:. In particular the Fourier transform is invertible (under suitable conditions).  More precisely, defining the "parity operator" that inverts time, : These equalities of operators require careful definition of the space of functions in question, defining equality of functions (equality at every point? equality almost everywhere?) and defining

Units and duality.

In mathematics, one often does not think of any units as being attached to the two variables and. But in physical applications, must have inverse units to the units of. For example, if is measured in seconds, should be in cycles per second for the formulas here to be valid. If the scale of is changed and is measured in units of 2 seconds, then either must be in the so-called "angular frequency", or one must insert some constant scale factor into some of the formulas. If is measured in units of

Uniform continuity and the Riemann–Lebesgue lemma.

The Fourier transform may be defined in some cases for non-integrable functions, but the Fourier transforms of integrable functions have several strong properties.  The Fourier transform of any integrable function is uniformly continuous and  By the "Riemann–Lebesgue lemma",  However, formula_9 need not be integrable. For example, the Fourier transform of the

Plancherel theorem and Parseval's theorem.

Let and be integrable, and let and be their Fourier transforms. If "f" ("x") and "g"("x") are also square-integrable, then the Parseval formula follows:  where the bar denotes complex conjugation.  The Plancherel theorem, which follows from the above, states that  Plancherel's theorem makes it possible to extend the Fourier transform, by a continuity argument, to a unitary operator on. On, this extension agrees with original Fourier transform defined on, thus enlarging

Poisson summation formula.

The Poisson summation formula (PSF) is an equation that relates the Fourier series coefficients of the periodic summation of a function to values of the function's continuous Fourier transform. The Poisson summation formula says that for sufficiently regular functions,  It has a variety of useful forms that are derived from the basic one by application of the Fourier transform's scaling and time-shifting properties. The formula has applications

Differentiation.

Suppose is an absolutely continuous differentiable function, and both and its derivative are integrable. Then the Fourier transform of the derivative is given by More generally, the Fourier transformation of the th derivative is given by  By applying the Fourier transform and using

Convolution theorem.

The Fourier transform translates between convolution and multiplication of functions. If and are integrable functions with Fourier transforms and respectively, then the Fourier transform of the convolution is given by the product of the Fourier transforms and (under other conventions for the definition of the Fourier transform a constant factor may appear).  This means that

Cross-correlation theorem.

In an analogous manner, it can be shown that if is the cross-correlation of

Eigenfunctions.

One important choice of an orthonormal basis for is given by the Hermite functions  where are the "probabilist's" Hermite polynomials, defined as  Under this convention for the Fourier transform, we have that  In other words, the Hermite functions form a complete orthonormal system of eigenfunctions for the Fourier transform on. However, this choice of eigenfunctions is not unique. There are only four different eigenvalues of the Fourier transform (±1 and ±) and any linear combination of eigenfunctions with the same eigenvalue gives

Connection with the Heisenberg group.

The Heisenberg group is a certain group of unitary operators on the Hilbert space of square integrable complex valued functions on the real line, generated by the translations and multiplication by,. These operators do not commute, as their (group) commutator is which is multiplication by the constant (independent of ) (the circle group of unit modulus complex numbers). As an abstract group, the Heisenberg group is the three-dimensional Lie group of triples, with the group law  Denote the

Complex domain.

The integral for the Fourier transform can be studied for complex values of its argument. Depending on the properties of, this might not converge off the real axis at all, or it might converge to a complex analytic function for all values of, or something in between.  The Paley–Wiener theorem says that is smooth (i.e., -times differentiable for all positive integers ) and compactly supported if and only if is a holomorphic function for which there exists a constant such that for any integer, for some constant. (In this case, is supported on.) This can be expressed by saying that is an entire function which is rapidly decreasing in (for fixed ) and of exponential growth in (uniformly in ).  (If is not smooth, but only, the statement still holds provided.) The space of such functions of a complex variable is called the Paley—Wiener space. This theorem has been generalised to semisimple Lie groups.  If is supported on the half-line, then is said to be "causal" because the impulse response function of a physically realisable filter must have this property, as no effect can precede its cause. Paley and Wiener showed that then extends to a holomorphic function on the complex lower half-plane which tends to zero as goes to infinity. The converse is false and it is not known how to characterise the Fourier transform of a causal function.

Laplace transform.

The Fourier transform is related to the Laplace transform, which is also used for the solution of differential equations and the analysis of filters.  It may happen that a function for which the Fourier integral does not converge on the real axis at all, nevertheless has a complex Fourier transform defined

Inversion.

If is complex analytic for, then  by Cauchy's integral theorem. Therefore, the Fourier inversion formula can use integration along different lines, parallel to the real axis.  Theorem: If for, and for some constants, then for any.  This theorem implies the Mellin inversion formula

Fourier transform on Euclidean space.

The Fourier transform can be defined in any arbitrary number of dimensions. As with the one-dimensional case, there are many conventions. For an integrable function, this article takes the definition:  where and are -dimensional vectors, and is the dot product of the vectors. The dot product is sometimes written as.  All of the basic properties listed above hold for the -dimensional Fourier transform, as do Plancherel's and Parseval's theorem. When the function is integrable, the Fourier transform is still uniformly continuous and the Riemann–Lebesgue lemma holds.

Uncertainty principle.

Generally speaking, the more concentrated is, the more spread out its Fourier transform must be. In particular, the scaling property of the Fourier transform may be seen as saying: if we squeeze a function in, its Fourier transform stretches out in. It is not possible to arbitrarily concentrate both a function and its Fourier transform.  The trade-off between the compaction of a function and its Fourier transform can be formalized in the form of an uncertainty principle by viewing a function and its Fourier transform as conjugate variables with respect to the symplectic form on the time–frequency domain: from the point of view of the linear canonical transformation, the Fourier transform is rotation by 90° in the time–frequency domain, and preserves the symplectic form.  Suppose is an integrable and square-integrable function. Without loss

Sine and cosine transforms.

Fourier's original formulation of the transform did not use complex numbers, but rather sines and cosines. Statisticians and others still use this form. An absolutely integrable function for which Fourier inversion holds good can be expanded in terms of genuine frequencies (avoiding negative frequencies, which are sometimes considered hard to interpret physically) by  This is called

Spherical harmonics.

Let the set of homogeneous harmonic polynomials of degree on be denoted by. The set consists of the solid spherical harmonics of degree. The solid spherical harmonics play a similar role in higher dimensions to the Hermite polynomials in dimension one. Specifically, if for some in, then. Let the set be the closure in of linear combinations of functions of the form where is

Restriction problems.

In higher dimensions it becomes interesting to study "restriction problems" for the Fourier transform. The Fourier transform of an integrable function is continuous and the restriction of this function to any set is defined. But for a square-integrable function the Fourier transform could be a general "class" of square integrable functions. As such, the restriction of the Fourier transform of an function cannot be defined on sets of measure 0. It is still an active area of study to understand restriction problems in for. Surprisingly, it is possible in some cases to define the restriction of a Fourier transform to a set, provided has non-zero curvature. The case when is the unit sphere in is of particular interest. In this case the Tomas–Stein restriction theorem states that the restriction of the Fourier transform

Fourier transform on function spaces.

On spaces.

On.

The definition of the Fourier transform by the integral formula  is valid for Lebesgue integrable functions ; that is,.  The Fourier transform is a bounded operator. This follows from the observation that  which shows that its

On.

Since compactly supported smooth functions are integrable and dense in, the Plancherel theorem allows us to extend the definition of the Fourier transform to general functions in by continuity arguments. The Fourier transform in is no longer given by an ordinary Lebesgue integral, although it can be computed by an improper integral, here meaning that for an function,

Formulas for general -dimensional functions.

In mathematics, a Fourier transform (FT) is a mathematical transform which decomposes a function (often a function of time, or a signal) into its constituent frequencies, such as the expression of a musical chord in terms of the volumes and frequencies of its constituent notes. The term "Fourier transform" refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of time.

Fourierova transformace je integrální transformace převádějící signál mezi časově a frekvenčně závislým vyjádřením pomocí harmonických signálů, tj. funkcí formula_1 a formula_2, obecně tedy funkcí komplexní exponenciály. Slouží pro převod signálů z časové oblasti do oblasti frekvenční. Signál může být buď ve spojitém či diskrétním čase.


Life.

Edmund Spenser was born in East Smithfield, London, around the year 1552, though there is still some ambiguity as to the exact date of his birth. His parenthood is obscure, but he was probably the son of John Spenser, a journeyman clothmaker. As a young boy, he was educated in London at the Merchant Taylors' School and matriculated as a sizar at Pembroke College, Cambridge. While at Cambridge he became a friend of Gabriel Harvey and later consulted him, despite their differing views on poetry. In 1578, he became for a short time secretary to John Young, Bishop of Rochester. In 1579, he published "The Shepheardes Calender" and around the same time married his first wife, Machabyas Childe. They had two children, Sylvanus (d. 1638) and Katherine.  In July 1580, Spenser went to Ireland in service of the newly appointed Lord Deputy, Arthur Grey, 14th Baron Grey de Wilton. Spenser served under Lord Gray with Walter Raleigh at the Siege of Smerwick massacre. When Lord Grey was recalled to England, Spenser stayed on in Ireland, having acquired other official posts and lands in the Munster Plantation. Raleigh acquired other nearby Munster estates confiscated in the Second Desmond Rebellion. Some time between 1587 and 1589, Spenser acquired his main estate at Kilcolman, near Doneraile in North Cork. He later bought a second holding to the south, at Rennie, on a rock overlooking the river Blackwater in North Cork. Its ruins are still visible today. A short distance away grew a tree, locally known as "Spenser's Oak" until it was destroyed in a lightning strike in the 1960s. Local legend has it that he penned some of "The Faerie Queene" under this tree.  In 1590, Spenser brought out the first three books of his most famous work, "The Faerie Queene", having travelled to London to publish and promote the work, with the likely assistance of Raleigh. He was successful enough to obtain a life pension of £50 a year from the Queen. He probably hoped to secure a place at court through his poetry, but his next significant publication boldly antagonised the queen's principal secretary, Lord Burghley (William Cecil), through its inclusion of the satirical "Mother Hubberd's Tale". He returned to Ireland.  In 1591, Spenser published a translation in verse of Joachim Du Bellay's sonnets, "Les Antiquités de Rome", which had been published in 1558. Spenser's version, "Ruines of Rome: by Bellay", may also have been influenced by Latin poems on the same subject, written by Jean or Janis Vitalis and published in 1576.  By 1594, Spenser's first wife had died, and in that year he married a much younger Elizabeth Boyle, sister of Richard Boyle, 1st Earl of Cork. He addressed to her the sonnet sequence "Amoretti". The marriage itself was celebrated in "Epithalamion". They had a son named Peregrine.  In 1596, Spenser wrote a prose pamphlet titled "A View of the Present State of Ireland". This piece, in the form of a dialogue, circulated in manuscript, remaining unpublished until the mid-seventeenth century. It is probable that it was kept out of print during the author's lifetime because of its inflammatory content. The pamphlet argued that Ireland would never be totally "pacified" by the English until its indigenous language and customs had been destroyed, if necessary by violence.  In 1598, during the Nine Years' War, Spenser was driven from his home by the native Irish forces of Aodh Ó Néill. His castle at Kilcolman was burned, and Ben Jonson, who may have had private information, asserted that one of his infant children died in the blaze.  In the year after being driven from his home, 1599, Spenser travelled to London, where he died at the age of forty-six – "for want of bread", according to Ben Jonson; one of Jonson's more doubtful statements, since Spenser had a payment to him authorised by the government and was due his pension. His coffin was carried to his grave in Poets' Corner in Westminster Abbey by other poets, who threw many pens and pieces of poetry into his grave with many tears. His second wife survived him and remarried twice. His sister Sarah, who had accompanied him to Ireland, married into the Travers family, and her descendants were prominent landowners in Cork for centuries.

Rhyme and reason.

Thomas Fuller, in "Worthies of England", included a story where the Queen told her treasurer, William Cecil, to pay Spenser one hundred pounds for his poetry. The treasurer, however, objected that the sum was too much. She said, "Then give him what is reason". Without receiving his payment in due time, Spenser gave the Queen this quatrain on one of her progresses:  <poem> I was promis'd on a time, To have a reason for my rhyme: From that time unto this season, I receiv'd nor rhyme nor reason. </poem>  She immediately ordered the treasurer pay Spenser the original £100.  This story seems to have attached itself to Spenser from Thomas Churchyard, who apparently had difficulty in getting payment of his pension, the only other pension Elizabeth awarded to a poet. Spenser seems to have had no difficulty in receiving payment when it was due as the pension was being collected for him by his publisher, Ponsonby.

"The Shepheardes Calender".

"The Shepheardes Calender" is Edmund Spenser's first major work, which appeared in 1579. It emulates Virgil's "Eclogues" of the first century BCE and the "Eclogues" of Mantuan by Baptista Mantuanus, a late medieval, early renaissance poet. An eclogue is a short pastoral poem that is in the form of a dialogue or soliloquy. Although all the months together form an entire year, each month stands alone as a separate poem. Editions of the late 16th and early 17th centuries include woodcuts for each month/poem, and thereby have a slight similarity to an emblem book which combines a number of self-contained pictures and texts, usually a short vignette, saying, or allegory with an accompanying illustration.

"The Faerie Queene".

Spenser's masterpiece is the epic poem "The Faerie Queene". The first three books of "The Faerie Queene" were published in 1590, and a second set of three books were published in 1596. Spenser originally indicated that he intended the poem to consist of twelve books, so the version of the poem we have today is incomplete. Despite this, it remains one of the longest poems in the English language. It is an allegorical work, and can be read (as Spenser presumably intended) on several levels of allegory, including as praise of Queen Elizabeth I. In a completely allegorical context, the poem follows several knights in an examination of several virtues. In Spenser's "A Letter of the Authors", he states that the entire epic poem is "cloudily enwrapped in allegorical devises", and that the aim behind "The Faerie Queene" was to "fashion a gentleman or noble person in virtuous and gentle discipline".

Shorter poems.

Spenser published numerous relatively short poems in the last decade of the sixteenth century, almost all of which consider love or sorrow. In 1591, he published "Complaints", a collection of poems that express complaints in mournful or mocking tones. Four years later, in 1595, Spenser published "Amoretti and Epithalamion". This volume contains eighty-nine sonnets commemorating his courtship of Elizabeth Boyle. In "Amoretti", Spenser uses subtle humour and parody while praising his beloved, reworking Petrarchism in his treatment of longing for a woman. "Epithalamion", similar to "Amoretti", deals in part with the unease in the development of a romantic and sexual relationship. It was written for his wedding to his young bride, Elizabeth Boyle. Some have speculated that the attention to disquiet in general reflects Spenser's personal anxieties at the time, as he was unable to complete his most significant work, "The Faerie Queene". In the following year Spenser released "Prothalamion", a wedding song written for the daughters of a duke, allegedly in hopes to gain favour in the court.

The Spenserian stanza and sonnet.

Spenser used a distinctive verse form, called the Spenserian stanza, in several works, including "The Faerie Queene". The stanza's main meter is iambic pentameter with a final line in iambic hexameter (having six feet or stresses, known as an Alexandrine), and the rhyme scheme is. He also used his own rhyme scheme for the sonnet. In a Spenserian sonnet, the last line of every quatrain is linked with the first line of the next one, yielding the rhyme scheme.

Influences.

Though Spenser was well read in classical literature, scholars have noted that his poetry does not rehash tradition, but rather is distinctly his. This individuality may have resulted, to some extent, from a lack of comprehension of the classics. Spenser strove to emulate such ancient Roman poets as Virgil and Ovid, whom he studied during his schooling, but many of his best-known works are notably divergent from those of his predecessors. The language of his poetry is purposely archaic, reminiscent of earlier works such as "The Canterbury Tales" of Geoffrey Chaucer and "Il Canzoniere" of Francesco Petrarca, whom Spenser greatly admired.  An Anglican and a devotee of the Protestant Queen Elizabeth, Spenser was particularly offended by the anti-Elizabethan propaganda that some Catholics circulated. Like most Protestants near the time of the Reformation, Spenser saw a Catholic church full of corruption, and he determined that it was not only the wrong religion but the anti-religion. This sentiment is an important backdrop for the battles of "The Faerie Queene".  Spenser was called "the Poet's Poet" by Charles Lamb, and was admired by John Milton, William Blake, William Wordsworth, John Keats, Lord Byron, Alfred Tennyson and others. Among his contemporaries Walter Raleigh wrote a commendatory poem to "The Faerie Queene" in 1590, in which he claims to admire and value Spenser's work more so than any other in the English language. John Milton in his "Areopagitica" mentions "our sage and serious poet Spenser, whom I dare be known to think a better teacher than Scotus or Aquinas". In the eighteenth century, Alexander Pope compared Spenser to "a mistress, whose faults we see, but love her with them all."

In his work "A View of the Present State of Irelande" (1596), Spenser discussed future plans to subjugate Ireland, the most recent rising, led by Hugh O'Neill, having demonstrated the futility of previous efforts. The work is partly a defence of Lord Arthur Grey de Wilton, who was appointed Lord Deputy of Ireland in 1580, and who greatly influenced Spenser's thinking on Ireland.  The goal of this piece was to show that Ireland was in great need of reform. Spenser believed that "Ireland is a diseased portion of the State, it must first be cured and reformed, before it could be in a position to appreciate the good sound laws and blessings of the nation". In "A View of the Present State of Ireland", Spenser categorises the "evils" of the Irish people into three prominent categories: laws, customs and religion. These three elements work together in creating the disruptive and degraded people. One example given in the work is the native law system called "Brehon law" which trumps the established law given by the English monarchy. This system has its own court and way of dealing with infractions. It has been passed down through the generations and Spenser views this system as a native backward custom which must be destroyed. (Brehon law methods of dealing with murder by imposing an "éraic", or fine, on the murderer's whole family particularly horrified the English, in whose Protestant view a murderer should die for his act.)  Spenser wished devoutly that the Irish language should be eradicated, writing that if children learn Irish before English, "Soe that the speach being Irish, the hart must needes be Irishe; for out of the aboundance of the hart, the tonge speaketh".  He pressed for a scorched earth policy in Ireland, noting that the destruction of crops and animals had been successful in crushing the Second Desmond Rebellion (1579–83), when, despite the rich and bountiful land:  "'Out of everye corner of the woode and glenns they came creepinge forth upon theire handes, for theire legges could not beare them; they looked Anatomies [of] death, they spake like ghostes, crying out of theire graves; they did eate of the carrions, happye wheare they could find them, yea, and one another soone after, in soe much as the verye carcasses they spared not to scrape out of theire graves; and if they found a plott of water-cresses or shamrockes, theyr they flocked as to a feast... in a shorte space there were none almost left, and a most populous and plentyfull countrye suddenly lefte voyde of man or beast: yett sure in all that warr, there perished not manye by the sworde, but all by the extreamytie of famine... they themselves had wrought'"

List of works.

1590:  1591:  1592:  1595:  1596: Posthumous:

Digital Archive.

Washington University in St. Louis professor Joseph Lowenstein, with the assistance of several undergraduate students, has been involved in creating, editing, and annotating a digital archive of the first publication of poet Edmund Spenser's collective works in 100 years. A large grant from the National Endowment for the Humanities has been given to support this ambitious project centralized at Washington University with support from other colleges in the United States.  |- style="text-align:center;"

Edmund Spenser (; 1552/1553 – 13 January 1599) was an English poet best known for "The Faerie Queene", an epic poem and fantastical allegory celebrating the Tudor dynasty and Elizabeth I. He is recognized as one of the premier craftsmen of nascent Modern English verse, and is often considered one of the greatest poets in the English language.

Edmund Spenser (asi 1552 – 13. ledna 1599) byl anglický básník a "poeta laueratus", jeden z vrcholných epiků anglické renesance. Ve svém díle zachytil dobovou atmosféru v Anglii na konci 16. století a rozklad aristokratické společnosti. Pro zápal, s nímž ve svých politických pamfletech prosazoval zničení irské kultury, je považován za kontroverzní osobu britských dějin.


Gameplay.

"Battlefield 2" is a sequel to "Battlefield Vietnam", with many changes to the popular gameplay of the original. Many of these new gameplay features were added to the game with teamwork and collaboration in mind. The new game engine includes improved physics, dynamic lighting, and more realistic material penetration.  "Battlefield 2" is a multiplayer video game played via the Internet or on a local area network. A single-player mode with three difficulty levels is included. Both player modes use the same maps and use "Battlefield"s conquest game mode. Single-player mode allows 16 computer-controlled players while Internet mode allows up to 64 players. Players can choose to play as the United States Marine Corps, the People's Liberation Army, or the "Middle Eastern Coalition". Additional factions are playable through the expansion packs, such as the European Union. Progress in the game is made via promotions which allow additional weapons to be unlocked. By playing the game on ranked servers, players are able to add to their global player statistics. These statistics are used to award promotions and other achievements.  In "Battlefield 2", players are divided into two opposing teams (which factions they represent is dependent upon the map). The key objective in "Battlefield 2" is to reduce the opposing teams tickets. Tickets represent an army's ability to reinforce their position on the battlefield; each team has only a limited supply of tickets, and each casualty on the battlefield reduces the number of available tickets. Control points represent key points on the map, and are represented by flags. Control points are "Battlefield 2"s spawn points, and one team possessing a significant majority of the control points causes the other teams tickets to gradually decrease, regardless of casualties. A round ends when one team's tickets gone, the round's timer ends, or if at any point a team holds no control points, and has no soldiers alive on the battlefield (meaning they are not present in any way on the battlefield).  "Battlefield 2"s two game modes are Conquest and Cooperative. The only difference between the two modes is that Cooperative includes computer-controlled players, whilst Conquest allows only human players. Results from Cooperative mode do not count toward global player statistics.

Infantry classes.

In "Battlefield 2", as with previous "Battlefield" titles, players are able to select from a variety of infantry classes. Each class of soldier is equipped with different weaponry appropriate to their role in the battle. Assault soldiers, for example, are general-purpose infantry with grenade-launcher equipped assault-rifles and extra armor, Medics carry first-aid equipment such as a field defibrillator, and Anti-Tank troopers are equipped with missiles which are effective against heavy armor.  Players are able to choose a class at the start of a match, or between dying and respawn. Players can also change their class by picking up a "kit" from the body of an incapacitated soldier, friendly or otherwise. Hence, an Assault soldier can become a Medic if they come across a fallen Medic. Player classes are divided in 'Heavy' (with reduced damage done to the torso, but lower stamina) and 'Light' (with standard multipliers, but higher stamina, thus able to sprint for a longer time).  Within the infantry class, there are four support classes with special abilities. The Engineer can repair with his wrench, the Medic can revive with his defibrillator paddles and heal, the Support can resupply ammunition with his ammunition bags and the sniper can place claymores and engage long distance targets. When one of these three classes occupies a vehicle (with the exception of the recon), nearby personnel and vehicles can be replenished, repaired or healed by being in close proximity.

Vehicles.

The various forces still use the trademark feature of the "Battlefield" series – the large stable of vehicles that any player can climb into and control. There are many different types of vehicles playable in "Battlefield 2", all based on real-life vehicles used by the militaries of different countries.  In contrast to "Battlefield 1942", "Battlefield 2" has only one purely water-based vehicle, the rigid-inflatable boat; however, the BTR-90, the MEC APC, can travel in water as well as the LAV-25 and the WZ 551, the USMC and PLA equivalents, respectively. The developers tried to design the game so that every vehicle would be weak to another type of vehicle, intending to create a situation similar to a game of rock-paper-scissors. For example, mobile anti-air was intended to effectively destroy helicopters, but are vulnerable against opposing tanks. Included within this relationship are stationary defenses such as light machine guns and anti-aircraft/TOW emplacements. The availability and number of certain vehicles are dependent on the map and its size as well as control points captured. Also, more vehicles become available to be used on the maps of expansion/booster packs. (see Maps). The USS Essex is the only naval ship featured in BF2, featuring two spawn points and aircraft spawn points, and is not drivable or destroyable, except for its Phalanx turrets.

Squads.

Players are able to form squads of up to six soldiers in order to more effectively work as a team. Up to nine squads are permitted per team; each squad has a number (automatically assigned) and name (usually a phonetic alphabet letter) for identification. Members of a squad have the ability to communicate with one another via "Battlefield 2"s integrated voice over IP (VoIP) system.  Squad leaders may assign their squad a variety of objectives (for example, moving to or attacking a specific location). Orders may also be given by the team's commander. Squad leaders are able to issue requests for commander assets (such as artillery fire) and have a direct VoIP channel to the commander.  Members of a squad may spawn near their squad leader, provided that the leader is not dead (or incapacitated), and that the team holds at least one control point. This feature allows squads to more quickly regroup after taking casualties.

Commander.

The commander position is an exclusive role played by one member of each team. Any member of a team may apply for the position, but priority is given to players of higher rank.  The commander alone has access to the "commander screen", an interface similar to that of a real-time strategy game. This allows the commander an overview of the battlefield as a whole, or zoom in and view parts of the map in real-time. The commander also has control of the various commander assets, which include artillery strikes, vehicle and supply drops, and UAV's. They can deploy them to assist their team. The commander can communicate with squads either by sending orders, or via VoIP voice communication. These tools allow the commander to strategically coordinate their forces on the battlefield.  A commander may resign at any point, freeing the position for other members of their team; they may also be forcibly removed by a successful mutiny vote conducted by their team (provided the server allows mutiny votes). Although the commander does not gain points by normal methods (kills, flag captures, etc.), their score is doubled at the end of the round if their team wins.  The commander position would be seen again in "Battlefield 2142" and "Battlefield 4".

Awards and unlockable weapons.

Players can earn awards (ribbons, badges, and medals) for certain in-game accomplishments. Badges and ribbons are the easiest to obtain, while medals are usually much harder, requiring more extensive play. As players ascend through the ranks they will gain the ability to unlock certain weapons. Each time a player is promoted to an eligible rank, they are given the opportunity to unlock one of seven unlockable weapons, one for each class, which they may subsequently use in place of the standard weapon for the given class.

Battlefield recorder.

A built-in game recorder records battles for subsequent replay. These files can be downloaded from a server which supports BattleRecorder directly after their respective game. Recorded battle files are around 1 to 8 megabytes in size and are played within the "Battlefield 2" engine. Camera angles can be changed (free roaming & selected player), as well as the speed, though there is no rewind capability. Files can be exported to AVI format. The Battlefield Recorder has facilitated the creation of various machinima. Usage of the PunkBuster service is mandatory for all official ranked "Battlefield 2" servers, but optional for unranked servers.

Maps.

"Battlefield 2" offers 15 maps for the players to play but shipped with 12. These maps are diverse, ranging from swamps such as Songhua Stalemate, to urban areas such as Strike at Karkand, to an unfinished dam known as Kubra Dam. The USMC is present in all maps and faces against either the MEC or the PLA depending on the map. The PLA is present in Far East theaters such as Dragon Valley and Daqing Oilfields. MEC is present in Middle East theaters such as Gulf of Oman and Zatar Wetlands. The BF2 series including the expansion and booster packs puts the map count at 29 maps.  "Battlefield 2" maps have 3 variations, each suited for a certain number of players. Each map has 16, 32, and 64 player-suggested variations in which the area of battlefield or playing field is relatively small, medium, and large, respectively. The only exceptions to this are Wake Island 2007, which is locked at 64-player size and the "Euro Force" maps, Operation Smokescreen, Great Wall, and Taraba Quarry, which have no 64-player size. 32 and 64 player maps are unavailable to offline players from retailers, but an option is given to download 64 Single player AI bot mods. Other contrasts between these variations other than the size are the number and position of control points and availability of vehicles. As a result, the gameplay of the map is different depending on the variation.

Plot.

The game is set in 2007 during a world war between various power blocs: the United States aided by the European Union and the United Kingdom are at war against Russia, China and the fictional Middle Eastern Coalition (MEC) aided by various insurgent groups.  There is no given reason as to how or why the war broke out, though one likely theory is for control of oil reserves. In-game, the European Union and the United States fight China and the MEC. It is mentioned in-game that the US and EU are allies and the EU has negotiated a truce with Russia, but it is unknown if China and the MEC are allies. The game also takes place in different fronts, as the Middle East and China are being invaded by US and EU forces, and the United States is being invaded by Chinese and MEC forces.

Additional content.

"Battlefield 2: Special Forces".

"Battlefield 2"'s first expansion pack, "Special Forces", first began its development sometime during or shortly before the release of the original "Battlefield 2" by DICE: "Battlefield" producer, Mike Doran, commented in August 2005 that "The truth is that work on "Battlefield 2: Special Forces" began several months ago." It was officially announced on July 14, 2005 and released on November 21 of the same year. The focus of the development was infantry-based combat as opposed to vehicle-centric combat from the original. As such, most of the additional content in the expansion pack can only be used by or for infantry.  The expansion pack provides eight maps, 6 playable factions, and ten more vehicles such as the AH-64D Apache and Mi-35 Hind, though all jets have been removed. In addition to these new contents, players have access to new equipment such as night vision goggles, tear gas, gas masks, zip lines and grappling hooks which can alter gameplay. There are eight more small arms weapons available such as the G36K/E and FN SCAR L/H and several weapons from the original are replaced. The expansion offers more awards in the form of badges, ribbons, and medals that players can earn. Finally, many of the weapons from the expansion may be used in the original "Battlefield 2".

Booster packs.

Booster packs are additional content released for "Battlefield 2" that are currently available for free download. The booster packs were later available in retail form as the "Booster Pack Collection", containing a DVD which features these packs, as well as being included in "The Complete Collection", containing a DVD with both the original game and all of the expansions/booster packs.  Booster packs add a significant amount of content to the game, but are different from expansion packs because they are intended to add to the original gameplay and not stand on their own (such as "Special Forces" does). The booster packs include new maps, vehicles, and a new European Union faction.  The two booster packs were included free of charge in the 1.50 update released on September 1, 2009.

"Euro Force".

"Battlefield 2: Euro Force" is the first booster pack, and was released on March 14, 2006. The booster pack allows players to play as a new European Union army, armed with new weapons and vehicles from the various countries of the EU. It is available for purchase online at the Electronic Arts download service, or as part of the retail "Booster Pack Collection". It was scheduled for release in February, but was delayed due to a substantial number of new bugs caused by the release of patch 1.2. It features a whole new army, 4 new vehicles, 3 new maps, and 7 new weapons such as the L85A2 with AG36 GL, the FAMAS, the HK53, the HK21, and the Benelli M4. Some of the vehicles for the EU military include the Challenger 2, Eurocopter Tiger, Leopard 2A6 and the Eurofighter. The maps include 'The Great Wall of China', against the People's Liberation Army of China, where the EU army is trying to gain a strong foothold in northern China, to reinforce their American allies in the south later on. 'Operation Smoke Screen' features the EU army fighting the MEC in the Middle East for precious oil fields, and the third map, 'Taraba Quarry', where the EU army is trying to reinforce American positions in the south. Mindful of the European plans, the MEC tries to stall the EU, where the Europeans must confront their enemies because that route is the only possible path along that side of the Caspian Sea.  It was made free with patch 1.5.

"Armored Fury".

"Battlefield 2: Armored Fury" is the second booster pack released for "Battlefield 2" and was released on June 6, 2006. It added three new maps, as well as two new vehicle classes: attack jets for close air support and reconnaissance helicopters that operate as a mobile UAV. The booster pack has the USMC defending U.S. soil from invasions from the PLA and MEC. Operation Midnight Sun features the Chinese landing at the Alaskan port Valdez where they are trying to secure much needed fuel from the pipeline. Operation Road Rage is a MEC vs. USMC map, where the MEC are using US Highways to transport units to industrial areas. Operation Harvest sees the United States trying to stall the MEC en route to the capital from the northwest, being blocked in a Pennsylvania Dutch farm, while waiting for reinforcements. New vehicles include Attack or Close Air Support aircraft such as the A-10 Thunderbolt II, Su-39 and the Nanchang Q-5 as well as new light utility helicopters such as MH-6 Little Bird, EC-635 and the Z-11. As well as the addition of new helicopters and planes, DICE also added the Muscle Car and Semi Truck. However, the proposed AV-8B Harrier was cut from the add-on due to balancing issues.  Like Euro Force, it was made free with patch 1.5.

Soundtrack.

The soundtrack of Battlefield 2 consists of 18 tracks composed and created by Fredrik Englund, David Tallroth, and Jonas Östholm.

Reception.

The game received widespread critical acclaim, garnering an aggregate score of 91/100 from 55 reviews on Metacritic. It received five stars out of five from publications Yahoo! Games, GameSpy, X-Play and Computer Gaming World. PC Gamer awarded it 94%, stating, "Its finely tuned maps and balanced gameplay prove that you "can" improve on perfection," and honored it as Game of the Year. GameSpot rated the game 9.3 out of 10 claiming that "when you experience "Battlefield 2" like it's meant to be played, with everyone working together and using real-time voice chat, the game quickly becomes unlike anything else that you've played before."  Some of the lower scores were reactions to the large amount of bugs and glitches in the initial release, including crash to desktop bugs and network problems. For example, Gaming Nexus (who awarded the game an 8.7 out of 10) reported, "I’ve had many cool experiences playing it and a lot of 'did I just see that' moments but all of that is crapped on by the bugs and quirks in the game."  GamesRadar approved of the game, awarding a 90%, but added a disclaimer that the gaming experience is best "if your machine is up to it". GameSpot's review agreed with the high system requirements noting that "the load times are one of the biggest gripes that we have, as you will spend quite a bit of time waiting for a game to start up, even on high-end machines...also a bit demanding in the hardware department."  "Battlefield 2" sold 1.2 million copies in its first month after release. Total sales by July 2006 were 2,225,000. It received a "Gold" sales award from the Entertainment and Leisure Software Publishers Association (ELSPA), indicating sales of at least 200,000 copies in the United Kingdom.  "Battlefield 2" won "PC Gamer US"s "Best Multiplayer Game 2005" and "Game of the Year 2005" awards. The magazine's Dan Stapleton wrote, "Few other games in the history of the medium have so effectively captured the visceral feeling of modern military combat in an urban environment". The editors of "Computer Games Magazine" presented "Battlefield 2" with their 2005 awards for "Best Action Game" and "Best Multiplayer", and named it the year's second-best computer game overall. They called it "perhaps the most thrilling example of how far shooters have come in the last few years."

Battlefield 2 is a 2005 first-person shooter military simulator video game, developed by Digital Illusions CE and published by Electronic Arts exclusively for Microsoft Windows as the third game in the "Battlefield" series.

Battlefield 2 (zkracováno na BF2) je akční počítačová hra pro PC, jejímž tématem je moderní válka. Jedná se o hru žánru FPS (střílečka z vlastního pohledu) s některými prvky strategie. Jako třetí díl série "Battlefield" ji v červenci 2005 vydala společnost Electronic Arts.


Procedure.

First, a voltage bias is applied and the tip is brought close to the sample by coarse sample-to-tip control, which is turned off when the tip and sample are sufficiently close. At close range, fine control of the tip in all three dimensions when near the sample is typically piezoelectric, maintaining tip-sample separation W typically in the 4-7 Å (0.4-0.7 nm) range, which is the equilibrium position between attractive (3<W<10Å) and repulsive (W<3Å) interactions. In this situation, the voltage bias will cause electrons to tunnel between the tip and sample, creating a current that can be measured. Once tunneling is established, the tip's bias and position with respect to the sample can be varied (with the details of this variation depending on the experiment) and data are obtained from the resulting changes in current.  If the tip is moved across the sample in the x-y plane, the changes in surface height and density of states causes changes in current. These changes are mapped in images. This change in current with respect to position can be measured itself, or the height, z, of the tip corresponding to a constant current can be measured. These two modes are called constant height mode and constant current mode, respectively. In constant current mode, feedback electronics adjust the height by a voltage to the piezoelectric height control mechanism. This leads to a height variation and thus the image comes from the tip topography across the sample and gives a constant charge density surface; this means contrast on the image is due to variations in charge density. In constant height mode, the voltage and height are both held constant while the current changes to keep the voltage from changing; this leads to an image made of current changes over the surface, which can be related to charge density. The benefit to using a constant height mode is that it is faster, as the piezoelectric movements require more time to register the height change in constant current mode than the current change in constant height mode. All images produced by STM are grayscale, with color optionally added in post-processing in order to visually emphasize important features.  In addition to scanning across the sample, information on the electronic structure at a given location in the sample can be obtained by sweeping voltage and measuring current at a specific location. This type of measurement is called scanning tunneling spectroscopy (STS) and typically results in a plot of the local density of states as a function of energy within the sample. The advantage of STM over other measurements of the density of states lies in its ability to make extremely local measurements: for example, the density of states at an impurity site can be compared to the density of states far from impurities.  Framerates of at least 25 Hz enable so called video-rate STM. Framerates up to 80 Hz are possible with fully working feedback that adjusts the height of the tip. Due to the line-by-line scanning motion, a proper comparison on the speed requires not only the framerate, but also the number of pixels in an image: with a framerate of 10 Hz and 100x100 pixels the tip moves with a line frequency of 1 kHz, whereas it moves with only with 500 Hz, when measuring with a faster framerate of 50 Hz but only 10x10 pixels. Video-rate STM can be used to scan surface diffusion.

Instrumentation.

The components of an STM include scanning tip, piezoelectric controlled height and x,y scanner, coarse sample-to-tip control, vibration isolation system, and computer.  The resolution of an image is limited by the radius of curvature of the scanning tip of the STM. Additionally, image artifacts can occur if the tip has two tips at the end rather than a single atom; this leads to “double-tip imaging,” a situation in which both tips contribute to the tunneling. Therefore, it has been essential to develop processes for consistently obtaining sharp, usable tips. Recently, carbon nanotubes have been used in this instance.  The tip is often made of tungsten or platinum-iridium, though gold is also used. Tungsten tips are usually made by electrochemical etching, and platinum-iridium tips by mechanical shearing.  Due to the extreme sensitivity of tunnel current to height, proper vibration insulation or an extremely rigid STM body is imperative for obtaining usable results. In the first STM by Binnig and Rohrer, magnetic levitation was used to keep the STM free from vibrations; now mechanical spring or gas spring systems are often used. Additionally, mechanisms for reducing eddy currents are sometimes implemented.  Maintaining the tip position with respect to the sample, scanning the sample and acquiring the data is computer controlled. The computer may also be used for enhancing the image with the help of image processing as well as performing quantitative measurements.

Other STM related studies.

Many other microscopy techniques have been developed based upon STM. These include photon scanning microscopy (PSTM), which uses an optical tip to tunnel photons; scanning tunneling potentiometry (STP), which measures electric potential across a surface; spin polarized scanning tunneling microscopy (SPSTM), which uses a ferromagnetic tip to tunnel spin-polarized electrons into a magnetic sample, multi-tip scanning tunneling microscopy which enables electrical measurements to be performed at the nanoscale, and atomic force microscopy (AFM), in which the force caused by interaction between the tip and sample is measured.  Other STM methods involve manipulating the tip in order to change the topography of the sample. This is attractive for several reasons. Firstly the STM has an atomically precise positioning system which allows very accurate atomic scale manipulation. Furthermore, after the surface is modified by the tip, it is a simple matter to then image with the same tip, without changing the instrument. IBM researchers developed a way to manipulate xenon atoms adsorbed on a nickel surface. This technique has been used to create electron "corrals" with a small number of adsorbed atoms, which allows the STM to be used to observe electron Friedel oscillations on the surface of the material. Aside from modifying the actual sample surface, one can also use the STM to tunnel electrons into a layer of electron beam photoresist on a sample, in order to do lithography. This has the advantage of offering more control of the exposure than traditional electron beam lithography. Another practical application of STM is atomic deposition of metals (gold, silver, tungsten, etc.) with any desired (pre-programmed) pattern, which can be used as contacts to nanodevices or as nanodevices themselves.  Variable temperature STM was used to investigate temperature dependency of molecular rotations on single crystalline surfaces. Rotating molecules appear blurred compared to non-rotating ones.  Recently groups have found they can use the STM tip to rotate individual bonds within single molecules. The electrical resistance of the molecule depends on the orientation of the bond, so the molecule effectively becomes a molecular switch.

Principle of operation.

Tunneling is a functioning concept that arises from quantum mechanics. Classically, an object hitting an impenetrable barrier will not pass through. In contrast, objects with a very small mass, such as the electron, have wavelike characteristics which permit such an event, referred to as tunneling.  Electrons behave as beams of energy, and in the presence of a potential "U"("z"), assuming 1-dimensional case, the energy levels "ψ"("z") of the electrons are given by solutions to Schrödinger’s equation,  where "ħ" is the reduced Planck’s constant, "z" is the position, and "m" is the mass of an electron. If an electron of energy "E" is incident upon an energy barrier of height "U"("z"), the electron wave function is a traveling wave solution,  where  if "E" > "U"("z"), which is true for a wave function inside the tip or inside the sample. Inside a barrier, "E" < "U"("z") so the wave functions which satisfy this are decaying waves,  where  quantifies the decay of the wave inside the barrier, with the barrier in the +"z" direction for formula_6. Knowing the wave function allows one to calculate the probability density for that electron to be found at some location. In the case of tunneling, the tip and sample wave functions overlap such that when under a bias, there is some finite probability to find the electron in the barrier region and even on the other side of the barrier. Let us assume the bias is "V" and the barrier width is "W". This probability, "P", that an electron at "z"=0 (left edge of barrier) can be found at "z"="W" (right edge of barrier) is proportional to the wave function squared,  If the bias is small, we can let "U" − "E" ≈ "φM" in the expression for "κ", where "φM", the work function, gives the minimum energy needed to bring an electron from an occupied level, the highest of which is at the Fermi level (for metals at "T"=0 kelvins), to vacuum level. When a small bias "V" is applied to the system, only electronic states very near the Fermi level, within "eV" (a product of electron charge and voltage, not to be confused here with electronvolt unit), are excited. These excited electrons can tunnel across the barrier. In other words, tunneling occurs mainly with electrons of energies near the Fermi level.  However, tunneling does require that there be an empty level of the same energy as the electron for the electron to tunnel into on the other side of the barrier. It is because of this restriction that the tunneling current can be related to the density of available or filled states in the sample. The current due to an applied voltage "V" (assume tunneling occurs sample to tip) depends on two factors: 1) the number of electrons between "E" and "eV" in the sample, and 2) the number among them which have corresponding free states to tunnel into on the other side of the barrier at the tip. The higher the density of available states the greater the tunneling current. When "V" is positive, electrons in the tip tunnel into empty states in the sample; for a negative bias, electrons tunnel out of occupied states in the sample into the tip.  Mathematically, this tunneling current is given by  One can sum the probability over energies between "E" − "eV" and "E" to get the number of states available in this energy range per unit volume, thereby finding the local density of states (LDOS) near the Fermi level. The LDOS near some energy "E" in an interval "ε" is given by  and the tunnel current at a small bias V is proportional to the LDOS near the Fermi level, which gives important information about the sample. It is desirable to use LDOS to express the current because this value does not change as the volume changes, while probability density does. Thus the tunneling current is given by  where ρ(0,"E") is the LDOS near the Fermi level of the sample at the sample surface. This current can also be expressed in terms of the LDOS near the Fermi level of the sample at the tip surface,  The exponential term in the above equations means that small variations in W greatly influence the tunnel current. If the separation is decreased by 1 Å, the current increases by an order of magnitude, and vice versa.  This approach fails to account for the "rate" at which electrons can pass the barrier. This rate should affect the tunnel current, so it can be treated using the Fermi's golden rule with the appropriate tunneling matrix element. John Bardeen solved this problem in his study of the metal-insulator-metal junction. He found that if he solved Schrödinger’s equation for each side of the junction separately to obtain the wave functions ψ and χ for each electrode, he could obtain the tunnel matrix, M, from the overlap of these two wave functions. This can be applied to STM by making the electrodes the tip and sample, assigning ψ and χ as sample and tip wave functions, respectively, and evaluating M at some surface S between the metal electrodes, where z=0 at the sample surface and z=W at the tip surface.  Now, Fermi’s Golden Rule gives the rate for electron transfer across the barrier, and is written  where δ(E–E) restricts tunneling to occur only between electron levels with the same energy. The tunnel matrix element, given by  is a description of the lower energy associated with the interaction of wave functions at the overlap, also called the resonance energy.  Summing over all the states gives the tunneling current as  where "f" is the Fermi function, ρ and ρ are the density of states in the sample and tip, respectively. The Fermi distribution function describes the filling of electron levels at a given temperature T.

Early invention.

An earlier, similar invention, the "Topografiner" of R. Young, J. Ward, and F. Scire from the NIST, relied on field emission. However, Young is credited by the Nobel Committee as the person who realized that it should be possible to achieve better resolution by using the tunnel effect. It was later discovered that an even higher resolution could be achieved by calculating the Doppler effect.

A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer (at IBM Zürich), the Nobel Prize in Physics in 1986. For an STM, good resolution is considered to be 0.1 nm lateral resolution and 0.01 nm (10 pm) depth resolution. With this resolution, individual atoms within materials are routinely imaged and manipulated. The STM can be used not only in ultra-high vacuum but also in air, water, and various other liquid or gas ambients, and at temperatures ranging from near zero kelvin to over 1000 °C.

STM (z angl. "Scanning Tunneling Microscope"), jehož české označení zní řádkovací tunelový mikroskop, je druhem neoptického mikroskopu, který mapuje povrch vodivého vzorku pomocí změny průběhu potenciálu, resp. proudu při pohybu vodivé sondy nad vzorkem. Přesněji se jedná o závislost množství elektronů (velikosti el. proudu), které tuneluje z materiálu do hrotu sondy a jež je exponenciálně závislé na vzdálenosti. STM byl vynalezen v roce 1981 Gerdem Binnigem a Heinrichem Rohrerem, kteří za tento objev získali Nobelovu cenu.


Background.

Robert Asprin was born in St. Johns, Michigan, and attended the University of Michigan at Ann Arbor, Michigan from 1964 through 1965. From 1965 through 1966 he served in the United States Army. He was married (twice) and had two children. He was active in science fiction fandom and in the early years of the Society for Creative Anachronism under the name "Yang the Nauseating", and co-founded the Great Dark Horde in 1971. He was also the founder and an influential member of the Dorsai Irregulars. In 1976, he was nominated for the Hugo Award for Best Dramatic Presentation for "The Capture", a cartoon slide show written by Asprin and drawn by Phil Foglio.

Early writing.

Asprin's first novel, "The Cold Cash War", an expansion of an earlier short story of the same title, was published in 1977.  Over the next few years, he created and edited (with his then-wife, Lynn Abbey) the "Thieves' World" series of shared world anthologies, credited as the first project of its type. Soon after the series hit its stride, many of the authors produced novels and stories outside the anthologies, beginning with "Beyond Sanctuary" by Janet Morris, the first "authorized" Thieves World novel, published in 1985. Janet Morris and Chris Morris went on to produce two more authorized Thieves' World "Beyond" novels and a series of related novels about their immortalized character, Tempus, and the Sacred Band of Stepsons. A series of graphic novels followed in the mid-1980s, and several other authors, including Andrew J. Offutt and David Drake, published novels about their characters. In 2002, Lynn Abbey resurrected the series with the novel "Sanctuary".  In 1978, Asprin began the "MythAdventures" series, chronicling the comic adventures of Skeeve and Aahz, with the book "Another Fine Myth". Originally illustrated by Frank Kelly Freas, and later by Phil Foglio, the highly pun-driven books follow a "demon" magician who has lost his powers and his inexperienced human apprentice as they travel through a variety of worlds in pursuit of finding their place in life, though under the guise of seeking wealth and glory. Some of the early "Myth" novels were later adapted as comic books by Foglio and others. The Myth books have passed through three publishing companies over the years: Donning Starblaze, Meisha Merlin and, as of 2008, Wildside Press.  In the 1990s, Asprin's "Phule" novels followed the humorous science-fiction exploits of a rag-tag company of the "Space Legion" and its wealthy and iconoclastic leader, Willard Phule.

Hiatus in writing career.

Due to a series of personal and financial problems, Asprin stopped writing in the 1990s. He had two books on The New York Times Best Seller list which piqued the interest of fans and the IRS. Unfortunately this came right at the time of an almost seven-year writing drought. He eventually negotiated an agreement with the IRS, that encouraged him to return to writing, and, in the late 1990s and early 2000s, he wrote several novels in collaboration with authors Peter Heck, Jody Lynn Nye, and Linda Evans. These novels included continuations of the "Myth" series and the "Phule" series as well as works in new series.

Later work.

One of Asprin's last projects was "NO Quarter", originally co-authored with Eric Del Carlo, and later edited by Teresa Patterson. It is a dark fantasy/suspense/ murder mystery novel set in the author's beloved New Orleans French Quarter. Although the novel's fantasy elements (voodoo and black magic, tarot readings and precognition, ghosts and mysticism) are secondary to the brutal murder that is the focus of the plot, it is set in the same milieu as Asprin's Griffen McCandles novels ("Dragons" series), "Dragons Luck" and "Dragons Wild". The two protagonists of "NO Quarter", Maestro and Bone, also appear as minor characters in the "Dragons" novels. Maestro, the mysterious pool shark and fencing master in "NO Quarter", is a highly fictionalized but recognizable self-portrait of the author. "NO Quarter" was published November 2009 by DarkStar Books.  Asprin's ofttimes co-author, Jody Lynn Nye, has completed one further Griffen McCandles novel, "Dragons Deal", and continued the "Myth Adventures" series. "Dragons Deal" was published by Ace in December 2010.

Death and aftermath.

Asprin died on May 22, 2008, of a heart attack at his home in New Orleans. He was found lying on a sofa with a Terry Pratchett novel still open in his hands. He was to have been the Guest of Honor at Marcon that weekend.  In 2008, his heirs donated his archive to the department of Rare Books and Special Collections at Northern Illinois University.

Robert Lynn Asprin (June 28, 1946 – May 22, 2008) was an American science fiction and fantasy author and active fan, best known for his humorous "MythAdventures" and "Phule's Company" series.

Robert Lynn Asprin (28. října 1946 St. Johns, Michigan – 22. května 2008 New Orleans, Louisiana) byl americký autor fantasy a science fiction literatury. Mezi jeho nejslavnější díla patří humorná série "Mýtus" a 12dílná antologie Svět zlodějů.


History.

The history of character codes illustrates the evolving need for machine-mediated character-based symbolic information over a distance, using once-novel electrical means. The earliest codes were based upon manual and hand-written encoding and cyphering systems, such as Bacon's cipher, Braille, International maritime signal flags, and the 4-digit encoding of Chinese characters for a Chinese telegraph code (Hans Schjellerup, 1869). With the adoption of electrical and electro-mechanical techniques these earliest codes were adapted to the new capabilities and limitations of the early machines. The earliest well-known electrically-transmitted character code, Morse code, introduced in the 1840s, used a system of four "symbols" (short signal, long signal, short space, long space) to generate codes of variable length. Though most commercial use of Morse code was via machinery, it was also used as a manual code, generatable by hand on a telegraph key and decipherable by ear, and persists in amateur radio use. Most codes are of fixed per-character length or variable-length sequences of fixed-length codes (e.g. Unicode). Common examples of character encoding systems include Morse code, the Baudot code, the American Standard Code for Information Interchange (ASCII) and Unicode. Unicode, a well defined and extensible encoding system, has supplanted most earlier character encodings, but the path of code development to the present is fairly well known.  The Baudot code, a five-bit encoding, was created by Émile Baudot in 1870, patented in 1874, modified by Donald Murray in 1901, and standardized by CCITT as International Telegraph Alphabet No. 2 (ITA2) in 1930. The name "baudot" has been erroneously applied to ITA2 and its many variants. ITA2 suffered from many shortcomings and was often "improved" by many equipment manufacturers, sometimes creating compatibility issues. In 1959 the U.S. military defined its Fieldata code, a six-or seven-bit code, introduced by the U.S. Army Signal Corps. While Fieldata addressed many of the then-modern issues (e.g. letter and digit codes arranged for machine collation), Fieldata fell short of its goals and was short-lived. In 1963 the first ASCII (American Standard Code for Information Interchange) code was released (X3.4-1963) by the ASCII committee (which contained at least one member of the Fieldata committee, W. F. Leubbert) which addressed most of the shortcomings of Fieldata, using a simpler code. Many of the changes were subtle, such as collatable character sets within certain numeric ranges. ASCII63 was a success, widely adopted by industry, and with the follow-up issue of the 1967 ASCII code (which added lower-case letters and fixed some "control code" issues) ASCII67 was adopted fairly widely. ASCII67's American-centric nature was somewhat addressed in the European ECMA-6 standard, which persists today as the base encoding for the UNICODE extended encoding strings. Somewhat historically isolated, IBM's Binary Coded Decimal (BCD) was a six-bit encoding scheme used by IBM in as early as 1959 in its 1401 and 1620 computers, and in its 7000 Series (for example, 704, 7040, 709 and 7090 computers), as well as in associated peripherals. BCD extended existing simple four-bit numeric encoding to include alphabetic and special characters, mapping it easily to punch-card encoding which was already in widespread use. It was the precursor to EBCDIC. For the most part, IBMs codes were used primarily with IBM equipment, which was more or less a closed ecosystem, and did not see much adoption outside of IBM "circles". IBM's Extended Binary Coded Decimal Interchange Code (usually abbreviated as EBCDIC) is an eight-bit encoding scheme developed in 1963.  The limitations of such sets soon became apparent, and a number of "ad hoc" methods were developed to extend them. The need to support more writing systems for different languages, including the CJK family of East Asian scripts, required support for a far larger number of characters and demanded a systematic approach to character encoding rather than the previous "ad hoc" approaches.  In trying to develop universally interchangeable character encodings, researchers in the 1980s faced the dilemma that on the one hand, it seemed necessary to add more bits to accommodate additional characters, but on the other hand, for the users of the relatively small character set of the Latin alphabet (who still constituted the majority of computer users), those additional bits were a colossal waste of then-scarce and expensive computing resources (as they would always be zeroed out for such users).  The compromise solution that was eventually found and developed into Unicode was to break the assumption (dating back to telegraph codes) that each character should always directly correspond to a particular sequence of bits. Instead, characters would first be mapped to a universal intermediate representation in the form of abstract numbers called code points. Code points would then be represented in a variety of ways and with various default numbers of bits per character (code units) depending on context. To encode code points higher than the length of the code unit, such as above 256 for 8-bit units, the solution was to implement variable-width encodings where an escape sequence would signal that subsequent bits should be parsed as a higher code point.

Terminology.

The character repertoire is an abstract set of more than one million characters found in a wide variety of scripts including Latin, Cyrillic, Chinese, Korean, Japanese, Hebrew, and Aramaic.  Other symbols such as musical notation are also included in the character repertoire. Both the Unicode and GB18030 standards have a character repertoire. As new characters are added to one standard, the other standard also adds those characters, to maintain parity.  The code unit size is equivalent to the bit measurement for the particular encoding:  "Example of a code unit:" Consider a string of the letters "abc" followed by (represented with 1 char32_t, 2 char16_t or 4 char8_t). That string contains:  The convention to refer to a character in Unicode is to start with 'U+' followed by the codepoint value in hexadecimal. The range of valid code points for the Unicode standard is U+0000 to U+10FFFF, inclusive, divided in 17 planes, identified by the numbers 0 to 16. Characters in the range U+0000 to U+FFFF are in plane 0, called the Basic Multilingual Plane (BMP). This plane contains most commonly-used characters. Characters in the range U+10000 to U+10FFFF in the other planes are called supplementary characters.  The following table shows examples of code point values: A code point is represented by a sequence of code units. The mapping is defined by the encoding. Thus, the number of code units required to represent a code point depends on the encoding:

Unicode encoding model.

Unicode and its parallel standard, the ISO/IEC 10646 Universal Character Set, together constitute a modern, unified character encoding. Rather than mapping characters directly to octets (bytes), they separately define what characters are available, corresponding natural numbers (code points), how those numbers are encoded as a series of fixed-size natural numbers (code units), and finally how those units are encoded as a stream of octets. The purpose of this decomposition is to establish a universal set of characters that can be encoded in a variety of ways. To describe this model correctly requires more precise terms than "character set" and "character encoding." The terms used in the modern model follow:  A character repertoire is the full set of abstract characters that a system supports. The repertoire may be closed, i.e. no additions are allowed without creating a new standard (as is the case with ASCII and most of the ISO-8859 series), or it may be open, allowing additions (as is the case with Unicode and to a limited extent the Windows code pages). The characters in a given repertoire reflect decisions that have been made about how to divide writing systems into basic information units. The basic variants of the Latin, Greek and Cyrillic alphabets can be broken down into letters, digits, punctuation, and a few "special characters" such as the space, which can all be arranged in simple linear sequences that are displayed in the same order they are read. But even with these alphabets, diacritics pose a complication: they can be regarded either as part of a single character containing a letter and diacritic (known as a precomposed character), or as separate characters. The former allows a far simpler text handling system but the latter allows any letter/diacritic combination to be used in text. Ligatures pose similar problems. Other writing systems, such as Arabic and Hebrew, are represented with more complex character repertoires due to the need to accommodate things like bidirectional text and glyphs that are joined together in different ways for different situations.  A coded character set (CCS) is a function that maps characters to "code points" (each code point represents one character). For example, in a given repertoire, the capital letter "A" in the Latin alphabet might be represented by the code point 65, the character "B" to 66, and so on. Multiple coded character sets may share the same repertoire; for example ISO/IEC 8859-1 and IBM code pages 037 and 500 all cover the same repertoire but map them to different code points.  A character encoding form (CEF) is the mapping of code points to "code units" to facilitate storage in a system that represents numbers as bit sequences of fixed length (i.e. practically any computer system). For example, a system that stores numeric information in 16-bit units can only directly represent code points 0 to 65,535 in each unit, but larger code points (say, 65,536 to 1.4 million) could be represented by using multiple 16-bit units. This correspondence is defined by a CEF.  Next, a character encoding scheme (CES) is the mapping of code units to a sequence of octets to facilitate storage on an octet-based file system or transmission over an octet-based network. Simple character encoding schemes include UTF-8, UTF-16BE, UTF-32BE, UTF-16LE or UTF-32LE; compound character encoding schemes, such as UTF-16, UTF-32 and ISO/IEC 2022, switch between several simple schemes by using byte order marks or escape sequences; compressing schemes try to minimise the number of bytes used per code unit (such as SCSU, BOCU, and Punycode).  Although UTF-32BE is a simpler CES, most systems working with Unicode use either UTF-8, which is backward compatible with fixed-width ASCII and maps Unicode code points to variable-width sequences of octets, or UTF-16BE, which is backward compatible with fixed-width UCS-2BE and maps Unicode code points to variable-width sequences of 16-bit words. See comparison of Unicode encodings for a detailed discussion.  Finally, there may be a higher level protocol which supplies additional information to select the particular variant of a Unicode character, particularly where there are regional variants that have been 'unified' in Unicode as the same character. An example is the XML attribute xml:lang.  The Unicode model uses the term character map for historical systems which directly assign a sequence of characters to a sequence of bytes, covering all of CCS, CEF and CES layers.

Character sets, character maps and code pages.

Historically, the terms "character encoding", "character map", "character set" and "code page" were synonymous in computer science, as the same standard would specify a repertoire of characters and how they were to be encoded into a stream of code units – usually with a single character per code unit. But now the terms have related but distinct meanings, due to efforts by standards bodies to use precise terminology when writing about and unifying many different encoding systems. Regardless, the terms are still used interchangeably, with "character set" being nearly ubiquitous.  A "code page" usually means a byte-oriented encoding, but with regard to some suite of encodings (covering different scripts), where many characters share the same codes in most or all those code pages. Well-known code page suites are "Windows" (based on Windows-1252) and "IBM"/"DOS" (based on code page 437), see Windows code page for details. Most, but not all, encodings referred to as code pages are single-byte encodings (but see octet on byte size.)  IBM's Character Data Representation Architecture (CDRA) designates with coded character set identifiers (CCSIDs) and each of which is variously called a "charset", "character set", "code page", or "CHARMAP".  The term "code page" does not occur in Unix or Linux where "charmap" is preferred, usually in the larger context of locales.  Contrasted to CCS above, a "character encoding" is a map from abstract characters to code words. A "character set" in HTTP (and MIME) parlance is the same as a character encoding (but not the same as CCS).  "Legacy encoding" is a term sometimes used to characterize old character encodings, but with an ambiguity of sense. Most of its use is in the context of Unicodification, where it refers to encodings that fail to cover all Unicode code points, or, more generally, using a somewhat different character repertoire: several code points representing one Unicode character, or versa (see e.g. code page 437). Some sources refer to an encoding as "legacy" only because it preceded Unicode. All Windows code pages are usually referred to as legacy, both because they antedate Unicode and because they are unable to represent all 2 possible Unicode code points.

Character encoding translation.

As a result of having many character encoding methods in use (and the need for backward compatibility with archived data), many computer programs have been developed to translate data between encoding schemes as a form of data transcoding. Some of these are cited below.  Cross-platform: Unix-like:  Windows:

In computing, data storage, and data transmission, character encoding is used to represent a repertoire of characters by some kind of encoding system. Depending on the abstraction level and context, corresponding code points and the resulting code space may be regarded as bit patterns, octets, natural numbers, electrical pulses, etc. A character encoding is used in computation, data storage, and transmission of textual data. "Character set", "character map", "codeset" and "code page" are related, but not identical, terms.

Kódování znaků nebo znakový kód () je ve výpočetní technice reprezentace znakové sady () nějakým (nejčastěji číselným) kódem. Po přijetí de facto standardů dálnopisných kódů bylo významným krokem standardizace vytvoření znakových kódů ASCII (1963) a EBCDIC (1964). Kód ASCII reprezentuje 33 řídicích a 95 tisknutelných znaků včetně malých a velkých písmen anglické abecedy, číslic a dalších symbolů pomocí 7bitových čísel; kód EBCDIC reprezentuje poněkud širší sadu znaků pomocí 8bitových čísel. Zatímco kód EBCDIC zůstal omezen na sálové počítače firmy IBM a jejich kopie, kód ASCII byl převzat různými národními i mezinárodními standardizačními organizacemi, například jako ISO/IEC 646 nebo T.50, a na jeho základě vzniklo množství národních variant používajících 7bitové kódy. Jejich velkou nevýhodou bylo, že symboly, jejichž používání se mezitím rozšířilo, nahrazují národními znaky, takže při volbě nevhodného kódování se např. texty programů mohou proměnit v nečitelnou změť znaků. Většího rozšíření se proto dočkaly 8bitové kódy, které zpravidla ponechávají kódy ASCII beze změn. Jedním 8bitovým kódem však nelze reprezentovat latinku, řecké písmo, cyrilici (azbuku), arabštinu a hebrejštinu, ani pokrýt všechny znaky latinky s diakritickými znaménky používanými v různých jazycích. Významné firmy jako Microsoft, IBM a Apple navíc vyvinuly vlastní osmibitové kódy, které přivedly kódování národních znaků na pokraj chaosu. Nejednotnost osmibitových kódování spolu s potřebou jednotné reprezentace asijských písem včetně rodiny CJK vedly okolo roku 1990 k vytvoření standardů Unicode a ISO 10646 vyvíjených ve vzájemné součinnosti, jejichž postupně uskutečňovaným záměrem je vytvořit jednotné kódovaní pro reprezentaci všech písem používaných na planetě Zemi.