Definition and illustration.

First example: the integers.

One of the most familiar groups is the set of integers formula_1 which consists of the numbers The following properties of integer addition serve as a model for

Definition.

A group is a set, "G", together with an operation ⋅ (called the "group law" of "G") that combines any two elements "a" and "b" to form another element, denoted or "ab". To qualify as a group, the set and operation,, must satisfy four requirements known as the "group axioms":  The result of the group operation may depend on the order of the operands. In other words, the result of combining element "a" with element "b" need not yield the same result as combining element "b" with element "a"; the equation may not be true for every two elements "a" and "b". This equation always holds in the group of integers under addition, because for any two integers (commutativity of addition). Groups for which the commutativity equation always holds are called "abelian groups" (in honor of Niels Henrik Abel). The symmetry group described in the following section is an example of a group that is not abelian.  The identity element of a group "G" is often written as 1 or 1, a notation inherited from the multiplicative identity. If

Second example: a symmetry group.

Two figures in the plane are congruent if one can be changed into the other using a combination of rotations, reflections, and translations. Any figure is congruent to itself. However, some figures are congruent to themselves in more than one way, and these extra congruences are called symmetries. A square has eight symmetries. These are:  These symmetries are functions. Each sends a point in the square to the corresponding point under the symmetry. For example, r sends a point to its rotation 90° clockwise around the square's center, and f sends a point to its reflection across the square's vertical middle line. Composing two of these symmetries gives another symmetry. These symmetries determine a group called the dihedral group of degree 4, denoted. The underlying set

History.

The modern concept of an abstract group developed out of several fields of mathematics. The original motivation for group theory was the quest for solutions of polynomial equations of degree higher than 4. The 19th-century French mathematician Évariste Galois, extending prior work of Paolo Ruffini and Joseph-Louis Lagrange, gave a criterion for the solvability of a particular polynomial equation in terms of the symmetry group of its roots (solutions). The elements of such a Galois group correspond to certain permutations of the roots. At first, Galois' ideas were rejected by his contemporaries, and published only posthumously. More general permutation groups were investigated in particular by Augustin Louis Cauchy. Arthur Cayley's "On the theory of groups, as depending on the symbolic equation θ = 1" (1854) gives the first abstract definition of a finite group.  Geometry was a second field in which groups were used systematically, especially symmetry groups as part of Felix Klein's 1872 Erlangen program. After novel geometries such as hyperbolic and projective geometry had emerged, Klein used group theory to organize them in a more coherent way. Further advancing these ideas, Sophus Lie founded the study of Lie groups in 1884.  The third field

Elementary consequences of the group axioms.

Basic facts about all groups that can be obtained directly from the group axioms are commonly subsumed under "elementary group theory". For example, repeated applications of the associativity axiom show that the unambiguity of generalizes to more than three factors. Because this implies that parentheses can be inserted anywhere within such a series of terms, parentheses are usually omitted.  The axioms may be weakened to assert only the existence of a left identity and left inverses. Both can be shown to be actually two-sided, so the resulting definition is equivalent to the one given above.

Uniqueness of identity element and inverses.

Two important consequences of the group axioms are the uniqueness of the identity element and the uniqueness of inverse elements. There can be only one identity element in a group, and each element in a group has exactly one inverse element. Thus, it is customary to speak of "the" identity, and "the" inverse of an element.  To prove the uniqueness of an

Division.

In groups, the existence of inverse elements implies that division is possible: given elements "a" and "b" of the group "G", there is exactly one solution "x" in "G" to the equation, namely. In fact, we have Uniqueness results by multiplying the two sides of the equation by. The element, often denoted, is called the "right quotient" of "b" by "a", or the result of the "right division" of "b" by "a".  Similarly there is exactly one solution "y" in "G" to the equation, namely. This solution is

Basic concepts.

To understand groups beyond the level of mere symbolic manipulations as above, more structural concepts have to be employed. There is a conceptual principle underlying all of the following notions: to take advantage of the structure offered by groups (which sets, being "structureless", do not have), constructions related to groups have to be "compatible" with the group operation. This compatibility manifests itself in the following notions in various ways. For example, groups can be related to each other via functions called group homomorphisms. By the mentioned principle, they are required to respect the group structures in a precise sense. The structure of groups can also be understood by breaking them into pieces called subgroups and quotient groups. The principle of "preserving structures"—a recurring topic in mathematics throughout—is an instance of working in a category, in this case the category of groups.

Group homomorphisms.

"Group homomorphisms" are functions that preserve group structure. A function between two groups and is called a "homomorphism" if the equation holds for all elements "g", "k" in "G". In other words, the result is the same when performing the group operation after or before applying the map "a". This requirement ensures that, and also for all "g" in "G". Thus a group homomorphism respects all the structure of

Subgroups.

Informally, a "subgroup" is a group "H" contained within a bigger one, "G". Concretely, the identity element of "G" is contained in "H", and whenever "h" and "h" are in "H", then so are and "h", so the elements of "H", equipped with the group operation on "G" restricted to "H", indeed form a group.  In the example above, the identity and the rotations constitute a subgroup highlighted in red in the group table above: any two rotations composed are still a rotation, and a rotation can be undone by (i.e., is inverse to) the complementary rotations 270° for

Cosets.

In many situations it is desirable to consider two group elements the same if they differ by an element of a given subgroup. For example, in D above, once a reflection is performed, the square never gets back to the r configuration by just applying the rotation operations (and no further reflections), i.e., the rotation operations are irrelevant to the question whether a reflection has been performed. Cosets are used to formalize this insight: a subgroup "H" defines left and right cosets, which can be thought of as translations of "H" by arbitrary group elements "g". In symbolic terms, the "left" and "right" cosets of "H" containing "g" are

Quotient groups.

In some situations the set of cosets of a subgroup can be endowed with a group law, giving a "quotient group" or "factor group". For this to be possible, the subgroup has to be normal. Given any normal subgroup "N", the quotient group is defined by  This set inherits a group operation (sometimes called coset multiplication, or coset addition) from the original group "G": for all "g" and "h" in "G". This definition is motivated by the idea (itself an instance of general structural considerations outlined above) that the map that associates to any element "g" its coset "gN" be a group homomorphism, or by general abstract considerations called universal properties. The coset serves as the identity in this group, and the inverse of "gN" in the quotient group is. The elements of the quotient group are "R" itself, which represents the identity, and. The group operation on the quotient is shown at the right. For example,. Both the subgroup as well as the corresponding quotient

Examples and applications.

Examples and applications of groups abound. A starting point is the group Z of integers with addition as group operation, introduced above. If instead of addition multiplication is considered, one obtains multiplicative groups. These groups are predecessors of important constructions in abstract algebra.  Groups are also applied in many other mathematical areas. Mathematical objects are often examined by associating groups to them and studying the properties of the corresponding groups. For example, Henri Poincaré founded what is now called algebraic topology by introducing the fundamental group. By means of this connection, topological properties such as proximity and continuity translate into properties of groups. For example, elements of the fundamental group are represented by loops. The second image at the right shows some loops in a plane minus a point. The blue loop is considered null-homotopic (and thus irrelevant), because it can be continuously shrunk to a point. The presence of the hole prevents the orange loop from being shrunk to a point. The fundamental group of the plane with a point deleted turns out to be infinite cyclic, generated by the orange loop (or any other loop winding once around the hole). This way, the fundamental group detects the hole.  In more recent applications, the influence has also been reversed to motivate geometric constructions by a group-theoretical background. In a similar vein, geometric group theory employs geometric concepts, for example in the study of hyperbolic groups. Further branches crucially applying groups include algebraic geometry and number theory.  In addition to the above theoretical applications, many practical applications of groups exist. Cryptography relies on the combination of the abstract group theory approach together with algorithmical knowledge obtained in computational group theory, in particular when implemented for finite groups. Applications of group theory are not restricted to mathematics; sciences such as physics, chemistry and computer science benefit from the concept.

Numbers.

Many number systems, such as the integers and the rationals enjoy a naturally given group structure. In some cases, such as with the rationals, both addition and multiplication operations give rise to group structures. Such number systems are predecessors to more general algebraic structures known as rings and fields. Further abstract algebraic concepts such as modules, vector spaces and algebras also form groups.

Integers.

The group of integers formula_1 under addition, denoted formula_4, has been described above. The integers, with the operation of multiplication instead of addition, formula_5 do "not" form a group. The closure,

Rationals.

The desire for the existence of multiplicative inverses suggests considering fractions Fractions of integers (with "b" nonzero) are known as rational numbers. The set of all such irreducible fractions is commonly denoted formula_8. There is still a minor obstacle for formula_9, the rationals with multiplication, being a group: because the rational number 0 does not have a multiplicative inverse (i.e., there is no "x" such that ), formula_9 is still not a group.  However, the set of all "nonzero" rational numbers formula_11 does form an abelian group under multiplication, generally denoted formula_12. Associativity and identity element axioms follow from the properties of integers. The closure requirement still holds true after removing zero, because the product of two nonzero rationals is never zero. Finally, the inverse of "a"/"b" is "b"/"a", therefore the axiom of the inverse element is satisfied.  The rational numbers (including 0) also form a group under addition. Intertwining addition and multiplication operations yields more complicated structures called rings and—if division is possible, such as in formula_8—fields, which occupy a central position in abstract algebra. Group theoretic arguments therefore underlie parts of the theory of those entities.

Modular arithmetic.

In modular arithmetic, two integers are added and then the sum is divided by a positive integer called the "modulus." The result of modular addition is the remainder of that division. For any modulus, "n", the set of integers from 0 to forms a group under modular addition: the inverse of any element "a" is, and 0 is the identity element. This is familiar from the addition of hours on the face of a clock: if the hour hand is on 9 and is advanced 4 hours, it ends up on 1, as shown at the right. This is expressed by saying that 9 + 4 equals 1 "modulo 12" or, in symbols, The group of integers modulo "n" is written formula_14 or formula_15.  For any prime number "p", there is also the multiplicative group of integers modulo "p". Its elements are the integers 1 to

Cyclic groups.

A "cyclic group" is a group all of whose elements are powers of a particular element "a". In multiplicative notation, the elements of the group are: where "a" means "a" ⋅ "a", and "a" stands for "a" ⋅ "a" ⋅ "a" = ("a" ⋅ "a" ⋅ "a") etc. Such an element "a" is called a generator or a primitive element of the group. In additive notation, the requirement for an element to be primitive is that each element of the group can be written as  In the groups Z/"n"Z introduced above, the element 1 is primitive, so these groups are cyclic. Indeed, each element is expressible as a sum all of whose terms are 1. Any cyclic group with "n" elements is isomorphic to this group. A second example for cyclic

Symmetry groups.

"Symmetry groups" are groups consisting of symmetries of given mathematical objects—be they of geometric nature, such as the introductory symmetry group of the square, or of algebraic nature, such as polynomial equations and their solutions. Conceptually, group theory can be thought of as the study of symmetry. Symmetries in mathematics greatly simplify the study of geometrical or analytical objects. A group is said to act on another mathematical object "X" if every group element performs some operation on "X" compatibly to the group law. In the rightmost example below, an element of order 7 of the (2,3,7) triangle group acts on the tiling by permuting the highlighted warped triangles (and the other ones, too). By a group action, the group pattern is connected to the structure of the object being acted on. In chemical fields, such as crystallography, space groups and point groups describe molecular symmetries and crystal symmetries. These symmetries underlie the chemical and physical behavior of these systems, and group theory enables simplification of quantum mechanical analysis of these properties. For example, group theory is used

General linear group and representation theory.

Matrix groups consist of matrices together with matrix multiplication. The "general linear group" consists of all invertible "n"-by-"n" matrices with real entries. Its subgroups are referred to as "matrix groups" or "linear groups". The dihedral group example mentioned above can be viewed as a (very small) matrix group. Another important matrix group is the special orthogonal group SO("n"). It describes all possible rotations in "n" dimensions. Via Euler angles, rotation matrices are used in computer graphics.  "Representation theory" is both an application of the group concept and important for

Galois groups.

"Galois groups" were developed to help solve polynomial equations by capturing their symmetry features. For example, the solutions of the quadratic equation are given by Exchanging "+" and "−" in the expression, i.e., permuting the two solutions of the equation can be viewed as a (very simple) group operation. Similar formulae are known for cubic and quartic equations, but do "not" exist in general for degree

Finite groups.

A group is called "finite" if it has a finite number of elements. The number of elements is called the order of the group. An important class is the "symmetric groups" S, the groups of permutations of "N" letters. For example, the symmetric group on 3 letters S is the group consisting of all possible orderings of the three letters "ABC", i.e., contains the elements "ABC", "ACB", "BAC", "BCA", "CAB", "CBA", in total 6 (factorial of 3) elements. This class is fundamental insofar as any finite group can be expressed as a subgroup of a symmetric group S for a suitable integer "N", according to Cayley's theorem. Parallel to the group of symmetries of the square above, S can also be interpreted as the group of symmetries of an equilateral triangle.  The order of an element "a" in a group "G" is the least positive integer "n" such that "a" = "e", where "a" represents  i.e., application of the operation ⋅ to "n" copies of "a". (If ⋅ represents multiplication, then "a" corresponds to the "n"th power of "a".) In infinite groups, such an "n" may not exist, in which case the order of "a" is said to be infinity. The order of an element equals the order of the cyclic subgroup generated by this element.  More sophisticated counting techniques, for example counting cosets, yield more precise statements about finite groups: Lagrange's Theorem states that for a finite group "G" the order of any finite subgroup "H" divides the order of "G". The Sylow theorems give a partial converse.  The dihedral group (discussed above) is a finite group of order 8. The order of r is 4, as is the order of the subgroup "R" it generates (see above). The order of the reflection elements f etc. is 2. Both orders divide 8, as predicted by Lagrange's theorem. The groups F above have order.

Classification of finite simple groups.

Mathematicians often strive for a complete classification (or list) of a mathematical notion. In the context of finite groups, this aim leads to difficult mathematics. According to Lagrange's theorem, finite groups of order "p", a prime number, are necessarily cyclic (abelian) groups Z. Groups of order "p" can also be shown to be abelian, a statement which does not generalize to order "p", as the non-abelian group D of order 8 = 2 above shows. Computer algebra systems can be

Groups with additional structure.

Many groups are simultaneously groups and examples of other mathematical structures. In the language of category theory, they are group objects in a category, meaning that they are objects (that is, examples of another mathematical structure) which come with transformations (called morphisms) that mimic the group axioms. For example, every group (as defined above) is also a set, so a group is a group object in the category of sets.

Topological groups.

Some topological spaces may be endowed with a group law. In order for the group law and the topology to interweave well, the group operations must be continuous functions, that is,, and "g" must not vary wildly if "g" and "h" vary only little. Such groups are called "topological groups," and they are the group objects in the category of topological spaces. The most basic examples are the reals R under addition,, and similarly with any other topological field such as the complex numbers

Lie groups.

"Lie groups" (in honor of Sophus Lie) are groups which also have a manifold structure, i.e., they are spaces looking locally like some Euclidean space of the appropriate dimension. Again, the additional structure, here the manifold structure, has to be compatible, i.e., the maps corresponding to multiplication and the inverse have to be smooth.  A standard example is the general linear group introduced above: it is an open subset of the space of all "n"-by-"n" matrices, because it is given by the inequality where "A" denotes an "n"-by-"n" matrix.  Lie groups are of fundamental importance in modern physics: Noether's theorem links continuous symmetries to conserved quantities.

Generalizations.

In abstract algebra, more general structures are defined by relaxing some of the axioms defining a group. For example, if the requirement that every element has an inverse is eliminated, the resulting algebraic structure is called a monoid. The natural numbers N (including 0) under addition form a monoid, as do the nonzero integers under multiplication, see above. There is a general method to formally add inverses to elements to any (abelian) monoid, much the same way as is derived from, known as the Grothendieck group. Groupoids are similar to groups except that the composition need not be defined for all "a" and "b". They arise in the study of more complicated forms of symmetry, often in topological and analytical structures, such as the fundamental groupoid or stacks. Finally, it is possible to generalize any of these concepts by replacing the binary operation with an arbitrary "n"-ary one (i.e., an operation taking "n" arguments). With the proper generalization of the group axioms this gives rise to an "n"-ary group. The table gives a list of several structures generalizing groups.

In mathematics, a group is a set equipped with a binary operation that combines any two elements to form a third element in such a way that four conditions called group axioms are satisfied, namely closure, associativity, identity and invertibility. One of the most familiar examples of a group is the set of integers together with the addition operation, but groups are encountered in numerous areas within and outside mathematics, and help focusing on essential structural aspects, by detaching them from the concrete nature of the subject of the study.

在数学中,群(group)是由一种集合以及一个二元运算所组成的,并且符合“群公理”。群公理包含下述四个性质的代数结构。这四个性质是封闭性、结合律、单位元和对于集合中所有元素存在逆元素。


Distribution, migration, and habitat.

Most shrike species have a Eurasian and African distribution, with just two breeding in North America (the loggerhead and great grey shrikes). No members of this family occur in South America or Australia, although one species reaches New Guinea. The shrikes vary in the extent of their ranges, with some species such as the great grey shrike ranging across the Northern Hemisphere to the Newton's fiscal which is restricted to the island of São Tomé.  They inhabit open habitats, especially steppe and savannah. A few species of shrikes are forest dwellers, seldom occurring in open habitats. Some species breed in northern latitudes during the summer, then migrate to warmer climes for the winter.

Description.

Shrikes are medium-sized birds with grey, brown, or black and white plumage. Most species are between and in size, however, the genus "Corvinella" with its extremely elongated tail feathers may reach up to in length. Their beaks are hooked, like those of a bird of prey, reflecting their predatory nature, and their calls are strident.

Behaviour.

Shrikes are known for their habit of catching insects and small vertebrates and impaling their bodies on thorns, the spikes on barbed-wire fences, or any available sharp point. This helps them to tear the flesh into smaller, more conveniently sized fragments, and serves as a cache so that the shrike can return to the uneaten portions at a later time. This same behaviour of impaling insects serves as an adaptation to eating the toxic lubber grasshopper, "Romalea microptera". The bird waits for 1–2 days for the toxins within the grasshopper to degrade, when they can then eat it.  Shrikes are territorial, and these territories are defended from other pairs. In migratory species, a breeding territory is defended in the breeding grounds and a smaller feeding territory is established during migration and in the wintering grounds. Where several species of shrikes exist together, competition for territories can be intense.  Shrikes make regular use of exposed perch sites, where they adopt a conspicuous upright stance. These sites are used to watch for prey and to advertise their presence to rivals.

Breeding.

Shrikes are generally monogamous breeders, although polygyny has been recorded in some species. Co-operative breeding, where younger birds help their parents raise the next generation of young, has been recorded in both species in the genera "Eurocephalus" and "Corvinella", as well as one species of "Lanius". Males attract females to their territory with well-stocked caches, which may include inedible but brightly coloured items. During courtship, the male performs a ritualised dance which includes actions that mimic the skewering of prey on thorns, and feeds the female. Shrikes make simple, cup-shaped nests from twigs and grasses, in bushes and the lower branches of trees.

Species in taxonomic order.

The family Laniidae was introduced (as Lanidia) by the French polymath Constantine Samuel Rafinesque in 1815.  FAMILY: LANIIDAE

Birds with similar names.

Other species with names including the word shrike, due to perceived similarities in morphology, are in the families: The helmetshrikes and bushshrikes were formerly included in Laniidae, but they are now known to be not particularly closely related to true shrikes.  The Australasian butcherbirds are not shrikes, although they occupy a similar ecological niche.

Shrikes () are carnivorous passerine birds of the family Laniidae. The family is composed of 33 species in four genera.

伯劳科(学名:)在鸟类全基因组测序分类系统中是鸟纲雀形目中的一个科。这是一种食肉的小型雀鸟,生性凶猛。


History.

Microsoft began developing.NET Framework in the late 1990s, originally under the name of Next Generation Windows Services (NGWS), as part of the.NET strategy. By late 2000, the first beta versions of.NET 1.0 were released.  In August 2000, Microsoft, and Intel worked to standardize Common Language Infrastructure (CLI) and C#. By December 2001, both were ratified Ecma International (ECMA) standards. International Organisation for Standardisation (ISO) followed in April 2003. The current version of ISO standards are ISO/IEC 23271:2012 and ISO/IEC 23270:2006.  While Microsoft and their partners hold patents for CLI and C#, ECMA and ISO require that all patents essential to implementation be made available under "reasonable and non-discriminatory terms". The firms agreed to meet these terms, and to make the patents available royalty-free. However, this did not apply for the part of.NET Framework not covered by ECMA-ISO standards, which included Windows Forms, ADO.NET, and ASP.NET. Patents that Microsoft holds in these areas may have deterred non-Microsoft implementations of the full framework.  On October 3, 2007, Microsoft announced that the source code for.NET Framework 3.5 libraries was to become available under the Microsoft Reference Source License (Ms-RSL). The source code repository became available online on January 16, 2008 and included BCL, ASP.NET, ADO.NET, Windows Forms, WPF, and XML. Scott Guthrie of Microsoft promised that LINQ, WCF, and WF libraries were being added. On November 12, 2014, Microsoft announced.NET Core, in an effort to include cross-platform support for.NET, the source release of Microsoft's CoreCLR implementation, source for the "entire [...] library stack" for.NET Core, and the adoption of a conventional ("bazaar"-like) open-source development model under the consolation stewardship of the.NET Foundation. Miguel de Icaza describes.NET Core as a "redesigned version of.NET that is based on the simplified version of the class libraries", and Microsoft's Immo Landwerth explained that.NET Core would be "the foundation of all future.NET platforms". At the time of the announcement, the initial release of the.NET Core project had been seeded with a subset of the libraries' source code and coincided with the relicensing of Microsoft's existing.NET reference source away from the restrictions of the Ms-RSL. Landwerth acknowledged the disadvantages of the formerly selected shared license, explaining that it made codename Rotor "a non-starter" as a community-developed open source project because it did not meet the criteria of an Open Source Initiative (OSI) approved license.  In November 2014, Microsoft also produced an update to its patent grants, which further extends the scope beyond its prior pledges. Prior projects like Mono existed in a legal grey area because Microsoft's earlier grants applied only to the technology in "covered specifications", including strictly the 4th editions each of ECMA-334 and ECMA-335. The new patent promise, however, places no ceiling on the specification version, and even extends to any.NET runtime technologies documented on MSDN that have not been formally specified by the ECMA group, if a project chooses to implement them. This allows Mono and other projects to maintain feature parity with modern.NET features that have been introduced since the 4th edition was published without being at risk of patent litigation over the implementation of those features. The new grant does maintain the restriction that any implementation must maintain minimum compliance with the mandatory parts of the CLI specification.  On March 31, 2016, Microsoft announced at Microsoft Build that they will completely relicense Mono under an MIT License even in scenarios where formerly a commercial license was needed. Microsoft also supplemented its prior patent promise for Mono, stating that they will not assert any "applicable patents" against parties that are "using, selling, offering for sale, importing, or distributing Mono." It was announced that the Mono Project was contributed to the.NET Foundation. These developments followed the acquisition of Xamarin, which began in February 2016 and was finished on March 18, 2016.  Microsoft's press release highlights that the cross-platform commitment now allows for a fully open-source, modern server-side.NET stack. Microsoft released the source code for WPF, Windows Forms and WinUI on December 4, 2018.  On May 8, 2019, Microsoft announced.NET 5.0, will be released in November 2020, which will be based on.NET Core.

Architecture.

Common Language Infrastructure.

Common Language Infrastructure (CLI) provides a language-neutral platform for application development and execution. By implementing the core aspects of.NET Framework within the scope of CLI, these functions will not be tied to one language but will be available across the many languages supported by the framework.

Common Language Runtime.

.NET Framework includes the Common Language Runtime (CLR). It serves as the execution engine of.NET Framework and offers many services such as memory management, type safety, exception handling, garbage collection, security and thread management. All programs written for.NET Framework are executed by the CLR.  Programs written for.NET Framework are compiled into Common Intermediate Language code (CIL), as opposed to being directly compiled into machine code. During execution, an architecture-specific just-in-time compiler (JIT) turns the CIL code into machine code.  With Microsoft's move to.NET Core, the CLI Virtual Execution System (VES) implementation is known as CoreCLR instead of CLR.

Assemblies.

Compiled CIL code is stored in CLI assemblies. As mandated by the specification, assemblies are stored in Portable Executable (PE) file format, common on Windows platform for all "dynamic-link library" (DLL) and "executable" EXE files. Each assembly consists of one or more files, one of which must contain a manifest bearing the metadata for the assembly. The complete name of an assembly (not to be confused with the file name on disk) contains its simple text name, version number, culture, and public key token. Assemblies are considered equivalent if they share the same complete name.  A private key can also be used by the creator of the assembly for strong naming. The public key token identifies which private key an assembly is signed with. Only the creator of the key pair (typically the person signing the assembly) can sign assemblies that have the same strong name as a prior version assembly, since the creator possesses the private key. Strong naming is required to add assemblies to Global Assembly Cache.  Starting with Visual Studio 2015,.NET Native compilation technology allows for the compilation of.NET code of Universal Windows Platform apps directly to machine code rather than CIL code, but the app must be written in either C# or Visual Basic.NET.

Class library.

.NET Framework includes an implementation of the CLI foundational Standard Libraries. The.NET Framework Class Library (FCL) is organized in a hierarchy of namespaces. Most of the built-in application programming interfaces (APIs) are part of either codice_1 or codice_2 namespaces. These class libraries implement many common functions, such as file reading and writing, graphic rendering, database interaction, and XML document manipulation. The class libraries are available for all CLI compliant languages. The FCL implements the CLI Base Class Library (BCL) and other class libraries—some are specified by CLI and other are Microsoft specific.  BCL includes a small subset of the entire class library and is the core set of classes that serve as the basic API of CLR. For.NET Framework most classes considered being part of BCL reside in codice_3, codice_4 and codice_5. BCL classes are available in.NET Framework as well as its alternative implementations including.NET Compact Framework, Microsoft Silverlight,.NET Core and Mono.  FCL refers to the entire class library that ships with.NET Framework. It includes an expanded set of libraries, including BCL, Windows Forms, ASP.NET, and Windows Presentation Foundation (WPF) but also extensions to the base class libraries ADO.NET, Language Integrated Query (LINQ), Windows Communication Foundation (WCF), and Workflow Foundation (WF). FCL is much larger in scope than standard libraries for languages like C++, and comparable in scope to standard libraries of Java.  With the introduction of alternative implementations (e.g., Silverlight), Microsoft introduced the concept of Portable Class Libraries (PCL) allowing a consuming library to run on more than one platform. With the further proliferation of.NET platforms, the PCL approach failed to scale (PCLs are defined intersections of API surface between two or more platforms). As the next evolutionary step of PCL, the.NET Standard Library was created retroactively based on the codice_6 based APIs found in UWP and Silverlight. New.NET platforms are encouraged to implement a version of the standard library allowing them to re-use extant third-party libraries to run without new versions of them. The.NET Standard Library allows an independent evolution of the library and app model layers within the.NET architecture.  NuGet is the package manager for all.NET platforms. It is used to retrieve third-party libraries into a.NET project with a global library feed at NuGet.org. Private feeds can be maintained separately, e.g., by a build server or a file system directory.  With Microsoft's move to.NET Core, the CLI foundational class libraries implementation is known as CoreFX instead of FCL.

App models.

Atop the class libraries, multiple app models are used to create apps..NET Framework supports Console, Windows Forms, Windows Presentation Foundation, ASP.NET and ASP.NET Core apps by default. Other app models are offered by alternative implementations of the.NET Framework. Console, UWP and ASP.NET Core are available on.NET Core. Mono is used to power Xamarin in app models for Android, iOS, and macOS. The retroactive architectural definition of app models showed up in early 2015 and was also applied to prior technologies like Windows Forms or WPF.

C++/CLI.

Microsoft introduced C++/CLI in Visual Studio 2005, which is a language and means of compiling Visual C++ programs to run within the.NET Framework. Some parts of the C++ program still run within an unmanaged Visual C++ Runtime, while specially modified parts are translated into CIL code and run with the.NET Framework's CLR.  Assemblies compiled using the C++/CLI compiler are termed mixed-mode assemblies, since they contain native and managed code in the same DLL. Such assemblies are more complex to reverse engineer, since.NET decompilers such as.NET Reflector reveal only the managed code.

Design principle.

Interoperability.

Because computer systems commonly require interaction between newer and older applications,.NET Framework provides means to access functions implemented in newer and older programs that execute outside.NET environment. Access to Component Object Model (COM) components is provided in codice_7 and codice_8 namespaces of the framework. Access to other functions is via Platform Invocation Services (P/Invoke). Access to.NET functions from native applications is via reverse P/Invoke function.

Language independence.

.NET Framework introduces a Common Type System (CTS) that defines all possible data types and programming constructs supported by CLR and how they may or may not interact conforming to CLI specification. Because of this feature,.NET Framework supports the exchange of types and object instances between libraries and applications written using any conforming.NET language.

Type safety.

CTS and the CLR used in.NET Framework also enforce type safety. This prevents ill-defined casts, wrong method invocations, and memory size issues when accessing an object. This also makes most CLI languages statically typed (with or without type inference). However, starting with.NET Framework 4.0, the Dynamic Language Runtime extended the CLR, allowing dynamically typed languages to be implemented atop the CLI.

Portability.

While Microsoft has never implemented the full framework on any system except Microsoft Windows, it has engineered the framework to be cross-platform, and implementations are available for other operating systems (see Silverlight and § Alternative implementations). Microsoft submitted the specifications for CLI (which includes the core class libraries, CTS, and CIL), C#, and C++/CLI to both Ecma International (ECMA) and International Organization for Standardization (ISO), making them available as official standards. This makes it possible for third parties to create compatible implementations of the framework and its languages on other platforms.

Security.

.NET Framework has its own security mechanism with two general features: Code Access Security (CAS), and validation and verification. CAS is based on evidence that is associated with a specific assembly. Typically the evidence is the source of the assembly (whether it is installed on the local machine or has been downloaded from the Internet). CAS uses evidence to determine the permissions granted to the code. Other code can demand that calling code be granted a specified permission. The demand causes CLR to perform a call stack walk: every assembly of each method in the call stack is checked for the required permission; if any assembly is not granted the permission a security exception is thrown.  Managed CIL bytecode is easier to reverse-engineer than native code, unless obfuscated. decompiler programs enable developers with no reverse-engineering skills to view the source code behind unobfuscated.NET assemblies. In contrast, apps compiled to native machine code are much harder to reverse-engineer, and source code is almost never produced successfully, mainly because of compiler optimizations and lack of reflection. This creates concerns in the business community over the possible loss of trade secrets and the bypassing of license control mechanisms. To mitigate this, Microsoft has included Dotfuscator Community Edition with Visual Studio.NET since 2002. Third-party obfuscation tools are also available from vendors such as VMware, V.i. Labs, Turbo, and Red Gate Software. Method-level encryption tools for.NET code are available from vendors such as SafeNet.

Memory management.

CLR frees the developer from the burden of managing memory (allocating and freeing up when done); it handles memory management itself by detecting when memory can be safely freed. Instantiations of.NET types (objects) are allocated from the managed heap; a pool of memory managed by CLR. As long as a reference to an object exists, which may be either direct, or via a graph of objects, the object is considered to be in use. When no reference to an object exists, and it cannot be reached or used, it becomes garbage, eligible for collection. .NET Framework includes a garbage collector (GC) which runs periodically, on a separate thread from the application's thread, that enumerates all the unusable objects and reclaims the memory allocated to them. It is a non-deterministic, compacting, mark-and-sweep garbage collector. GC runs only when a set amount of memory has been used or there is enough pressure for memory on the system. Since it is not guaranteed when the conditions to reclaim memory are reached, GC runs are non-deterministic. Each.NET application has a set of roots, which are pointers to objects on the managed heap ("managed objects"). These include references to static objects, objects defined as local variables or method parameters currently in scope, and objects referred to by CPU registers. When GC runs, it pauses the application and then, for each object referred to in the root, it recursively enumerates all the objects reachable from the root objects and marks them as reachable. It uses CLI metadata and reflection to discover the objects encapsulated by an object, and then recursively walk them. It then enumerates all the objects on the heap (which were initially allocated contiguously) using reflection. All objects not marked as reachable are garbage. This is the "mark" phase. Since the memory held by garbage is of no consequence, it is considered free space. However, this leaves chunks of free space between objects which were initially contiguous. The objects are then "compacted" together to make free space on the managed heap contiguous again. Any reference to an object invalidated by moving the object is updated by GC to reflect the new location. The application is resumed after garbage collection ends. The latest version of.NET framework uses concurrent garbage collection along with user code, making pauses unnoticeable, because it is done in the background.  The garbage collector used by.NET Framework is also "generational". Objects are assigned a "generation". Newly created objects are tagged "Generation 0". Objects that survive one garbage collection are tagged "Generation 1". Generation 1 objects that survive another collection are "Generation 2". The framework uses up to Generation 2 objects. Higher generation objects are garbage collected less often than lower generation objects. This raises the efficiency of garbage collection, as older objects tend to have longer lifetimes than newer objects. By ignoring older objects in most collection runs, fewer checks and compaction operations are needed in total.

Performance.

When an application is first launched, the.NET Framework compiles the CIL code into executable code using its just-in-time compiler, and caches the executable program into the.NET Native Image Cache. Due to caching, the application launches faster for subsequent launches, although the first launch is usually slower. To speed up the first launch, developers may use the Native Image Generator utility to manually ahead-of-time compile and cache any.NET application.  The garbage collector, which is integrated into the environment, can introduce unanticipated delays of execution over which the developer has little direct control. "In large applications, the number of objects that the garbage collector needs to work with can become very large, which means it can take a very long time to visit and rearrange all of them." .NET Framework provides support for calling Streaming SIMD Extensions (SSE) via managed code from April 2014 in Visual Studio 2013 Update 2. However, Mono has provided support for SIMD Extensions as of version 2.2 within the namespace in 2009. Mono's lead developer Miguel de Icaza has expressed hope that this SIMD support will be adopted by CLR's ECMA standard. Streaming SIMD Extensions have been available in x86 CPUs since the introduction of the Pentium III. Some other architectures such as ARM and MIPS also have SIMD extensions. In case the CPU lacks support for those extensions, the instructions are simulated in software.

Alternative implementations.

.NET Framework is the predominant implementation of.NET technologies. Other implementations for parts of the framework exist. Although the runtime engine is described by an ECMA-ISO specification, other implementations of it may be encumbered by patent issues; ISO standards may include the disclaimer, "Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights." It is harder to develop alternatives to FCL, which is not described by an open standard and may be subject to copyright restrictions. Also, parts of FCL have Windows-specific functions and behavior, so implementation on non-Windows platforms can be problematic.  Some alternative implementations of parts of the framework are listed here.

Licensing.

Microsoft managed code frameworks and their components are licensed as follows:

.NET Framework (pronounced as ""dot net"") is a software framework developed by Microsoft that runs primarily on Microsoft Windows. It includes a large class library called Framework Class Library (FCL) and provides language interoperability (each language can use code written in other languages) across several programming languages. Programs written for.NET Framework execute in a software environment (in contrast to a hardware environment) named the Common Language Runtime (CLR). The CLR is an application virtual machine that provides services such as security, memory management, and exception handling. As such, computer code written using.NET Framework is called "managed code". FCL and CLR together constitute the.NET Framework.

-{zh-hans:.NET框架(英语:.NET Framework);zh-hant:.NET Framework}-是由微软开发,一个致力于敏捷软件开发(agile software development)、快速应用开发(rapid application development)、平台独立性和网络透明化的软件框架。.NET是微软为2000年代对服务器和桌上型软件工程迈出的第一步。.NET包含许多有助于因特网和内部网应用迅捷开发的技术。


Comparison with free software licenses.

A free software license grants users of that software the rights to use for any purpose, modify and redistribute creative works and software, both of which are forbidden by the defaults of copyright, and generally not granted with proprietary software. These licenses typically include a disclaimer of warranty, but this feature is not unique to free software.  Copyleft licenses also include a key addition provision that must be followed in order to copy or modify the software, that requires the user to provide source code for the work and to distribute their modifications under the same license (or sometimes a compatible one); thus effectively protecting derivative works from losing the original permissions and being used in proprietary programs.  Unlike EULAs, free software licenses do not work as contractual extensions to existing legislation. No agreement between parties is ever held, because a copyright license is simply a declaration of permissions on something that otherwise would be disallowed by default under copyright law.

Shrink-wrap and click-wrap licenses.

The term shrink-wrap license refers colloquially to any software license agreement which is enclosed within a software package and is inaccessible to the customer until after purchase. Typically, the license agreement is printed on paper included inside the boxed software. It may also be presented to the user on-screen during installation, in which case the license is sometimes referred to as a click-wrap license. The inability of the customer to review the license agreement before purchasing the software has caused such licenses to run afoul of legal challenges in some cases.  Whether shrink-wrap licenses are legally binding differs between jurisdictions, though a majority of jurisdictions hold such licenses to be enforceable. At particular issue is the difference in opinion between two US courts in "Klocek v. Gateway" and "Brower v. Gateway". Both cases involved a shrink-wrapped license document provided by the online vendor of a computer system. The terms of the shrink-wrapped license were not provided at the time of purchase, but were rather included with the shipped product as a printed document. The license required the customer to return the product within a limited time frame if the license was not agreed to. In "Brower", New York's state appeals court ruled that the terms of the shrink-wrapped license document were enforceable because the customer's assent was evident by its failure to return the merchandise within the 30 days specified by the document. The U.S. District Court of Kansas in "Klocek" ruled that the contract of sale was complete at the time of the transaction, and the additional shipped terms contained in a document similar to that in "Brower" did not constitute a contract, because the customer never agreed to them when the contract of sale was completed.  Further, in "ProCD v. Zeidenberg", the license was ruled enforceable because it was necessary for the customer to assent to the terms of the agreement by clicking on an "I Agree" button in order to install the software. In Specht v. Netscape Communications Corp., however, the licensee was able to download and install the software without first being required to review and positively assent to the terms of the agreement, and so the license was held to be unenforceable.  Click-wrap license agreements refer to website based contract formation (see iLan Systems, Inc. v. Netscout Service Level Corp.). A common example of this occurs where a user must affirmatively assent to license terms of a website, by "clicking" "yes" on a pop-up, in order to access website features. This is therefore analogous to shrink-wrap licenses, where a buyer implied agrees to license terms by first removing the software package's shrink-wrap and then utilizing the software itself. In both types of analysis, focus is on the actions of end user and asks whether there is an explicit or implicit acceptance of the additional licensing terms.

Product liability.

Most licenses for software sold at retail disclaim (as far as local laws permit) any warranty on the performance of the software and limit liability for any damages to the purchase price of the software. One well-known case which upheld such a disclaimer is Mortenson v. Timberline.

Patent.

In addition to the implied exhaustion doctrine, the distributor may include patent licenses along with software.

Reverse engineering.

Forms often prohibit users from reverse engineering. This may also serve to make it difficult to develop third-party software which interoperates with the licensed software, thus increasing the value of the publisher's solutions through decreased customer choice. In the United States, EULA provisions can preempt the reverse engineering rights implied by fair use, c.f. Bowers v. Baystate Technologies.  Some licenses purport to prohibit a user's right to release data on the performance of the software, but this has yet to be challenged in court.

Enforceability of EULAs in the United States.

The enforceability of an EULA depends on several factors, one of them being the court in which the case is heard. Some courts that have addressed the validity of the shrinkwrap license agreements have found some EULAs to be invalid, characterizing them as contracts of adhesion, unconscionable, and/or unacceptable pursuant to the U.C.C.—see, for instance, "Step-Saver Data Systems, Inc. v. Wyse Technology", "Vault Corp. v. Quaid Software Ltd.". Other courts have determined that the shrinkwrap license agreement is valid and enforceable: see "ProCD, Inc. v. Zeidenberg", "Microsoft v. Harmony Computers", "Novell v. Network Trade Center", and "Ariz. Cartridge Remanufacturers Ass'n v. Lexmark Int'l, Inc." may have some bearing as well. No court has ruled on the validity of EULAs generally; decisions are limited to particular provisions and terms.  The 7th Circuit and 8th Circuit subscribe to the "licensed and not sold" argument, while most other circuits do not. In addition, the contracts' enforceability depends on whether the state has passed the Uniform Computer Information Transactions Act (UCITA) or Anti-UCITA]] ([[UCITA Bomb Shelter) laws. In Anti-UCITA states, the [[Uniform Commercial Code]] (UCC) has been amended to either specifically define software as a good (thus making it fall under the UCC), or to disallow contracts which specify that the terms of contract are subject to the laws of a state that has passed UCITA.  Recently, publishers have begun to [[encryption|encrypt]] their software packages to make it impossible for a user to install the software without either agreeing to the license agreement or violating the [[Digital Millennium Copyright Act]] (DMCA) and [[WIPO Copyright Treaty|foreign counterparts]].  The DMCA specifically provides for reverse engineering of software for interoperability purposes, so there was some controversy as to whether software license agreement clauses which restrict this are enforceable. The [[United States Court of Appeals for the Eighth Circuit|8th Circuit]] case of "Davidson & Associates v. Jung" determined that such clauses are enforceable, following the [[Federal Circuit]] decision of "[[Bowers v. Baystate Technologies|Baystate v. Bowers]]".

Criticism.

[[Jerry Pournelle]] wrote in 1983, "I've seen no evidence to show that... Levitical agreements — full of "Thou Shalt Nots" — have any effect on piracy". He gave an example of an EULA that was impossible for a user to comply with, stating "Come on, fellows. No one expects these agreements to be kept". Noting that in practice many companies were more generous to their customers than their EULAs required, Pournelle wondered "Why, then, do they insist on making their customers sign 'agreements' that the customer has no intention of keeping, and which the company "knows" won't be kept?... Must we continue making hypocrites out of both publishers and customers?"  One common criticism of end-user license agreements is that they are often far too lengthy for users to devote the time to thoroughly read them. In March 2012, the [[PayPal]] end-user license agreement was 36,275 words long and in May 2011 the [[iTunes]] agreement was 56 pages long. News sources reporting these findings asserted that the vast majority of users do not read the documents because of their length.  Several companies have parodied this belief that users do not read the end-user-license agreements by adding unusual clauses, knowing that few users will ever read them. As an [[April Fool's Day]] joke, [[Gamestation]] added a clause stating that users who placed an order on April 1, 2010 agreed to irrevocably [[Deal with the Devil|give their soul]] to the company, which 7,500 users agreed to. Although there was a checkbox to exempt out of the "immortal soul" clause, few users checked it and thus Gamestation concluded that 88% of their users did not read the agreement. The program "PC Pitstop" included a clause in their end-user license agreement stating that anybody who read the clause and contacted the company would receive a monetary reward, but it took four months and over 3,000 software downloads before anybody collected it. During the installation of version 4 of the Advanced Query Tool the installer measured the elapsed time between the appearance and the acceptance of the end-user license agreements to calculate the average reading speed. If the agreements were accepted fast enough a dialog window “congratulated” the users to their absurdly high reading speed of several hundred words per second. "[[South Park]]" parodied this in the episode "[[HumancentiPad]]", where [[Kyle Broflovski|Kyle]] had neglected to read the terms of service for his last iTunes update and therefore inadvertently agreed to have [[Apple Inc.|Apple]] employees experiment upon him.  End-user license agreements have also been criticized for containing terms that impose onerous obligations on consumers. For example, Clickwrapped, a service that rates consumer companies according to how well they respect the rights of users, reports that they increasingly include a term that prevents a user from suing the company in court.  In a recent article published by Kevin Litman-Navarro for the New York Times, titled "We Read 150 Privacy Policies. They Were an Incomprehensible Disaster", the complexity of 150 terms from popular sites like Facebook, Airbnb, etc. were analyzed and comprehended. As a result, for example, the majority of licenses require college or higher-level degrees: "To be successful in college, people need to understand texts with a score of 1300. People in the professions, like doctors and lawyers, should be able to understand materials with scores of 1440, while ninth graders should understand texts that score above 1050 to be on track for college or a career by the time they graduate. Many privacy policies exceed these standards."  [[Category:Terms of service]]

External links.

[[Category:Software licenses]] [[Category:Contract law]]

An end-user license agreement (EULA, ) is a legal contract entered into between a software developer or vendor and the user of the software, often where the software has been purchased by the user from an intermediary such as a retailer. A EULA specifies in detail the rights and restrictions which apply to the use of the software.

最终用户许可协议(英语:end-user license agreements,英文缩写:英语:EULA)是指软件开发者或发行者授权用户使用特定软件产品时的规定,大多私有软件附带此协议,如不接受则无法安装。不过自由软件则较少使用这个协议,如GPL是一种授权协议,但不限于最终用户。一个例外是Firefox拥有注册商标,Mozilla基金会使用最终用户许可协议保护其商标。


Etymology.

The Arabic word "" () simply means 'the city'. Before the advent of Islam, the city was known as (; ). The word "Yathrib" has been

Overview.

, the city of Medina has a population of 1,183,205.. Later the city's name was changed to "Madīna-tu n-Nabī" or "al-Madīnatu 'l-Munawwarah" (, "the lighted city" or "the radiant city"). Medina is celebrated for containing "al-Masjid an-Nabawi" and as the city which gave refuge to him and his followers, and so ranks as the second holiest city of Islam, after Mecca. Muhammad was buried in Medina, under the Green Dome, as were the first two Rashidun caliphs, Abu Bakr and Umar, who were buried next to him in what used to be Muhammad's house.  Medina is north of Mecca and about from the Red Sea coast. It is situated in the most fertile part of all the Hejazi territory, the streams of the vicinity tending to converge in this locality.

Religious significance in Islam.

Medina's importance as a religious site derives from the presence of "al-Masjid an-Nabawi". The mosque was expanded by the Umayyad Caliph Al-Walid I. Mount Uhud is a mountain north of Medina which was the site of the second battle between Muslim and Meccan forces.  After Muhammad migrated to Madinah, he built Quba' Mosque and offered prayers in it. He would ride a camel or walk to the mosque every Saturday to offer 2 rakaats of prayers. Quba' Mosque is now located in the metropolitan area of Medina. It was destroyed by lightning, probably about 850 CE, and the graves were almost forgotten. In 892, the place was cleared up, the graves located and a fine mosque built, which was destroyed by fire in 1257 CE and almost immediately rebuilt. It was restored by Qaitbay, the Egyptian ruler, in 1487.  Muslims are encouraged to perform 2 rakaat of Sunnah prayer at this Quba' Mosque. According to a hadith from Sunan Ibn Majah, Sahl ibn Hunayf reported that Muhammad said, "“Whoever purifies himself in his house,

History.

Pre-7th century.

By the fourth century, Arab tribes began to encroach from Yemen, and there were three prominent Jewish tribes that inhabited the city into the 7th century CE: the Banu Qaynuqa, the Banu Qurayza, and Banu Nadir. Ibn Khordadbeh later reported that during the Persian Empire's domination in Hejaz, the Banu Qurayza served as tax collectors for the Persian Shah. The situation changed after the arrival from Yemen of two new Arab tribes named Banu Aus (or Banu 'Aws) and Banu Khazraj. At first, these tribes were allied with Jewish rulers, but later they revolted and became independent.

Muhammad's arrival.

In 622 CE/1 AH, Muhammad and around 70 Meccan Muhajirun believers left Mecca for sanctuary in Yathrib, an event that transformed the religious and political landscape of the city completely; the longstanding enmity between the Aus and Khazraj tribes was dampened as many of the two Arab tribes and some local Jews embraced Islam. Muhammad, linked to the Khazraj through his great-grandmother, was agreed on as civic leader. The Muslim converts native to Yathrib of whatever background—pagan Arab or Jewish—were called "Ansar" ("the Patrons" or "the Helpers"), while the Muslims would pay the Zakat tax.  According to Ibn Ishaq, the local pagan Arab tribes, the Muslim "Muhajirun" from Mecca, the local Muslims ("Ansar"), and

Battle of Badr.

The Battle of Badr was a key battle in the early days of Islam and a turning point in Muhammad's struggle with his opponents among the Quraysh in Mecca. In the spring of 624, Muhammad received word from his intelligence sources that a trade caravan, commanded by Abu Sufyan ibn Harb, Chieftain of the Meccan Quraysh, and guarded by thirty to forty men, was travelling from Syria back to Mecca. Muhammad gathered an army of 313 men, the largest army the Muslims had put in the field yet. However, many early Muslim sources, including the Quran, indicate that no serious fighting was expected, and the future Caliph Uthman ibn Affan stayed behind to care for his sick wife.  As the caravan approached Medina, Abu Sufyan began hearing from travellers and riders about Muhammad's planned ambush. He sent a messenger named Damdam to Mecca to warn the Quraysh and get reinforcements. Alarmed, the Quraysh assembled an army of 900–1,000 men to rescue the caravan. Many of the Qurayshi nobles, including Amr ibn Hishām, Walid ibn Utba, Shaiba, and Umayyah ibn Khalaf, joined the army. However, some of the army was

Battle of Uhud.

In 625, Abu Sufyan, who paid tax to the Byzantine empire regularly, once again led a Meccan force against Medina. Muhammad marched out to meet the force but before reaching the battle, about one third of the troops under Abd-Allah ibn Ubayy withdrew. With a smaller force, the Muslim army had to find a strategy to gain the upper hand. A group of archers were ordered to stay on a hill to keep an eye on the Meccan's cavalry forces and to provide protection at the rear of the Muslim's army. As the battle heated up, the Meccans were forced to somewhat retreat. The battle front was pushed further and further away from the archers, whom, from the start of the battle, had really nothing to do but watch.

Battle of the Trench.

In 627, Abu Sufyan once more led Meccan forces against Medina. Because the people of Medina had dug a trench to further protect the city, this event became known as the Battle of the Trench. After a protracted siege and various skirmishes, the Meccans withdrew again. During the siege, Abu Sufyan had contacted the remaining Jewish tribe of Banu Qurayza and formed an agreement with them, to attack the defenders from behind the lines. It was however discovered by the Muslims and thwarted. This was in breach of the Constitution of Medina and after

Capital city of Muhammad and the Rashidun Caliphate.

In the ten years following the hijra, Medina formed the base from which Muhammad and the Muslim army attacked and were attacked, and it was from here that he marched on Mecca, entering it without battle in 629 CE/8 AH, all parties acquiescing to his leadership. Afterwards, however, despite Muhammad's tribal connection to Mecca and the ongoing importance of the Meccan Ka'bah for Islamic pilgrimage (Hajj), Muhammad returned to Medina, which remained for some years the most important city of Islam and the capital of the early caliphate.  "Yathrib" was renamed Medina from "Madinat al-Nabi" ("city of the Prophet" in Arabic) in honour of Muhammad's prophethood and

World War I to Saudi control.

In the beginning of the 20th century, during World War I, Medina witnessed one of the longest sieges in history. Medina was a city of the Turkish Ottoman Empire. Local rule was in the hands of the Hashemite clan as Sharifs or Emirs of Mecca. Fakhri Pasha was the Ottoman governor of Medina. Ali bin Hussein, the Sharif of Mecca and leader of the Hashemite clan, revolted against the Caliph in Constantinople (Istanbul) and sided with Great Britain. The city of Medina

Modern Medina.

Today, Medina ("Madinah" officially), in addition to being the second most important Islamic pilgrimage destination after Mecca, is an important regional capital of the western Saudi Arabian province of Al

Geography.

Medina is located in the Hijaz Region north-western of the country, east to the Red Sea, and above sea level. It lies at the meeting-point of longitude 39o36' east and latitude 24o28' north. It covers an area of about.

Topography.

Medina is a desert oasis surrounded by mountains and volcanic hills, as mentioned in several references and sources. It was known as Yathrib in Writings of ancient Maeniand, this is obvious evidence that the population structure of this desert oasis is a combination of north Arabs and South Arabs, who settled there and built their civilization during the thousand years before Christ.  The soil surrounding Medina consists

Climate.

Medina has a hot desert climate (Köppen climate classification "BWh"). Summers are extremely hot with daytime temperatures averaging about with nights about.

Demographics.

As of 2018, the recorded population was 2,188,138, with an annual increase of 50,800 people which represents a growth rate of 2.32%. Being a destination of Muslims from around the world, Medina witnesses illegal stay of visitors after performing Hajj or Umrah, despite the strict rules the government apply. However, The head of Central Hajj Committee Prince Khalid Al-Faisal stated in 2018 that the numbers of illegal staying visitors have dropped by 29%.

Religion.

As with most cities in Saudi Arabia, Islam is the religion adhered by the majority of the population of Medina. Sunnis of different schools (Hanafi, Maliki,

Economy.

Historically, Medina is known for growing dates. As of 1920, 139 varieties of dates were being grown in the area. Medina also was known for growing many types of vegetables.  Medina has two industrial areas, the biggest was established in 2003 with a total area of 10,000,000 m2, and managed by Modon. It is located 50 km from Prince Mohammed bin Abdulaziz International Airport, and 200 km from Yanbu Commercial Port,

Education.

Higher Education.

Taibah University is a public university providing higher education for the residents of Madinah Region,it has 28 colleges 16 of which are in Medina. It offers 89 academic programs and enrolls about 69210 students of both males and females.  The Islamic University, established in 1961, is the oldest higher education institution in the region, with around 22000 students enrolled. It offers majors in Sharia, Qur'an, Usul al-din, Hadith, and Arabic. The university offers Bachelor of Arts degrees and also

Primary and Secondary Education.

The General Administration of Education is the governing body of education in Madinah Region, it operates 724 public schools for males and 773 for females in Madinah Region..  Taibah High School is

Transport.

Air.

Medina is served by Prince Mohammad bin Abdulaziz International Airport, located about from the city centre. It handles domestic flights, while it has scheduled international services to regional destinations. It is the fourth busiest airport in Saudi Arabia, handling 8,144,790

High Speed Rail.

The Haramain High Speed Railway (HHR) came into operation in 2018, linking Medina with Mecca, and passes through three stations: Jeddah, King Abdul Aziz International Airport, and King Abdullah

Roads.

Two major highways connects Medina to the rest of the country. Highway 15 runs north through Khaybar to Tabuk, and south through Jeddah, Mecca, Abha, to Najran. Highway 60, runs east through Buraidah to Riyadh, and west through Badr to Yanbu.

Bus System.

The bus transport system in Medina was established in 2012 by the Al-Madinah Region Development Authority (MMDA) and operated by SAPTCO. The newly established bus system includes 10 lines connects different regions of the city to Al-Masjid Al-Nabawi and the downtown area, and serves around 20,000 passengers on a daily

Culture.

Landmarks.

Al-Masjid Al-Nabawi (the prophet's mosque), is the main destination in Medina, Muslim visitors from all over the world comes to pray at the mosque, and visit the Tomb of Muhammad, and visit Al-Baqi' cemetery, where Fatimah the daughter of Muhammed, Al-Hasan the grandson of Muhammed, and many of the companions of Muhammed are buried.  Quba Mosque which is the first mosque built in Islam, is also a main destination for the visitors of Medina. In 2015, the MMDA announced Darb Al-Sunnah (Sunnah Path) Project, which aims to develop and transform Quba Road ( a 3km road connecting Al-Masjid Al-Nabawi to Quba Mosque) to an avenue, paving the whole road for pedestrians, and providing service facilities to the visitors. The project also aims to revive the Sunnah where Muhammed used

Museums.

Al-Madinah Museum: It exhibits Al-Madina heritage and history featuring different archaeological collections, visual galleries and rare images that related to Al-Medina. It is also includes the Hejaz Railway Museum.

Arts.

Medina Arts Center, founded in 2018 and operated by the MMDA's Cultural Program, focuses on modern and contemporary arts. The center aims to enhance arts and enrich the artistic and cultural movement of the society, and empowering artists of all groups and ages. As of February 2020, it held more than 13 group and solo art galleries, and holds weekly workshops and discussions. The center is located in King Fahd Park on the south-west side of the Quba Mosque on an area of 8,200 m2.  Dar Al-Qalam Center for Arabic Calligraphy, is a center dedicated to the art of Arabic Calligraphy. It is located north-west

Sports.

Medina is the home of two sports clubs Al-Ansar FC,

Accent.

Being located in the Hejaz Region; Medina is one of the

Destruction of heritage.

Saudi Arabia is hostile to any reverence given to historical or religious places of significance for fear that it may give rise to "shirk" (idolatry). As a consequence, under Saudi rule, Medina has suffered from considerable destruction of its physical heritage including the loss of many buildings over a thousand years old. Critics have described this as "Saudi vandalism" and claim that in Medina and Mecca over the last 50 years, 300 historic sites linked to Muhammad, his family or companions have been lost. In Medina, examples of historic sites which have been destroyed include three of the Seven Mosques, the Raj'at ash-Shams Mosque.

Medina, also transliterated as Madīnah (), is the capital of the Al-Madinah Region in Saudi Arabia. At the city's heart is "al-Masjid an-Nabawi" ('The Prophet's Mosque'), which is the burial place of the Islamic prophet, Muhammad. Medina is one of the three holiest cities in Islam, the other two being Mecca and Jerusalem.

麦地那( ',意谓「光芒四射的城市」)原名雅特里布"',伊斯兰教第二大圣城,后又称圣城( "Madinat al-Nabi"),该城位于沙特阿拉伯西部,为内陆高原城市。与麦加,耶路撒冷一起被称为伊斯兰教三大圣地。


Personal life.

Victor-Marie Hugo was born on 26 February 1802 in in the eastern region of. The youngest of three sons of Joseph Léopold Sigisbert Hugo (1774–1828) a general in the Napoleonic army, and Sophie Trébuchet (1772–1821); his brothers were (1798–1855) and (1800–1837). Léopold Hugo wrote to his son that he had been conceived on one of the highest peaks in the Vosges Mountains, on a journey from Lunéville to Besançon. "This elevated origin", he went on, "seems to have had effects on you so that your muse is now continually sublime." Hugo believed himself to have been conceived on 24 June 1801, which is the origin of Jean Valjean's prisoner number 24601.  Léopold Hugo was a freethinking republican who considered Napoleon a hero; by contrast, Sophie Hugo was a Catholic Royalist who was intimately involved with her possible lover Géneral, Victor Hugo’s godfather, who was executed in 1812 for plotting against Napoléon.  Hugo's childhood was a period of national political turmoil. Napoléon was proclaimed Emperor of the French two years after Hugo's birth, and the Bourbon Monarchy was restored before his 13th birthday. The opposing political and religious views of Hugo's parents reflected the forces that would battle for supremacy in France throughout his life: Hugo's father was a high-ranking officer in Napoléon's army until he failed in Spain (one of the reasons why his name is not present on the ).  Because Hugo's father was an officer, the family moved frequently from posting to posting, as far as Italy and Spain. Hugo learned much from these travels. On a childhood family trip to Naples, Hugo saw the vast Alpine passes and the snowy peaks, the magnificently blue Mediterranean, and Rome during its festivities. Though he was only five years old at the time, he remembered the six-month-long trip vividly. They stayed in Naples for a few months and then headed back to Paris.  At the beginning of her marriage, Hugo's mother Sophie followed her husband to posts in Italy (where Léopold served as governor of Avellino) and Spain (where he took charge of three Spanish provinces). Weary of the constant moving required by military life and at odds with her husband's lack of Catholic beliefs, Sophie separated temporarily from Léopold in 1803 and settled in Paris with

Writings.

Hugo published his first novel the year following his marriage (, 1823), and his second three years later ("Bug-Jargal", 1826). Between 1829 and 1840, he published five more volumes of poetry (, 1829;, 1831;, 1835;, 1837; and, 1840), cementing his reputation as one of the greatest elegiac and lyric poets of his time.  Like many young writers of his generation, Hugo was profoundly influenced by, the famous figure in the literary movement of Romanticism and France's pre-eminent literary figure during the early 19th century. In his youth, Hugo resolved to be " or nothing", and his life would come to parallel that of his predecessor in many ways. Like, Hugo furthered the cause of Romanticism, became involved in politics (though mostly as a champion of Republicanism), and was forced into exile due to his political stances.  The precocious passion and eloquence of Hugo's early work brought success and fame at an early age. His first collection of poetry () was published in 1822 when he was only 20 years old and earned him a royal pension from Louis XVIII. Though the poems were admired for their spontaneous fervour and fluency, the collection that followed four years later in 1826 () revealed Hugo to be a great poet, a natural master of lyric and creative song.  Victor Hugo's first mature work of fiction was first published in February 1829 by Charles Gosselin without the author's name and reflected the acute social conscience that would infuse his later work. ("The Last Day of a Condemned Man") would have a profound influence on later writers such as Albert Camus, Charles Dickens, and Fyodor Dostoyevsky., a documentary short story about a real-life murderer who had been executed in France, appeared in 1834 and was later considered by Hugo himself to be a precursor to his great work on social injustice,.  Hugo became the figurehead of the Romantic literary movement with the plays "Cromwell" (1827) and "Hernani" (1830). "Hernani" announced the arrival of French romanticism: performed at the Comédie-Française, it was greeted with several nights of rioting as romantics and traditionalists clashed over the play's deliberate disregard for neo-classical rules. Hugo's popularity as a playwright grew with subsequent plays, such as "Marion Delorme" (1831), "The King Amuses Himself" (1832), and "Ruy Blas" (1838).  Hugo's novel ("The Hunchback of Notre-Dame") was published in 1831 and quickly translated into other languages across Europe. One of the effects of the novel was to shame the City of Paris into restoring the much-neglected Cathedral of Notre Dame, which was attracting thousands of tourists who had read the popular novel. The book also inspired a renewed appreciation for pre-Renaissance buildings, which

Political life and exile.

After three unsuccessful attempts, Hugo was finally elected to the in 1841, solidifying his position in the world of French arts and letters. A group of French academicians, particularly, were fighting against the "romantic evolution" and had managed to delay Victor Hugo's election. Thereafter, he became increasingly involved in French politics.  He was ennobled and elevated to the peerage by King in 1845 and entered the Higher Chamber as a, where he spoke against the death penalty and social injustice, and in favour of freedom of the press and self-government for Poland.  In 1848, Hugo was elected to the National Assembly of the Second Republic as a conservative. In 1849, he broke with the conservatives when he gave a noted speech calling for the end of misery and poverty. Other speeches called for universal suffrage and free education for all children. Hugo's advocacy to abolish the death penalty was renowned internationally.  These parliamentary speeches are published in. Scroll down to the heading and subsequent pages.  When Louis Napoleon (Napoleon III) seized complete power in 1851, establishing an anti-parliamentary constitution, Hugo openly declared him a traitor to France. He relocated to Brussels, then Jersey, from which he was expelled for supporting a Jersey newspaper that had criticised Queen Victoria and finally settled with his family at Hauteville House in Saint Peter Port, Guernsey, where he would live in exile from October 1855 until 1870.  While in exile, Hugo published his famous political pamphlets against Napoleon III, and. The pamphlets were banned in France but nonetheless had a strong impact there. He also composed or published some of his best work during his period in Guernsey, including, and three widely praised collections of poetry (, 1853;, 1856; and, 1859).  Like most of his contemporaries, Victor Hugo held colonialist views towards Africans. In a speech delivered on 18 May 1879, he declared that the Mediterranean Sea formed a natural divide between " ultimate civilisation and [...] utter barbarism," adding "God offers Africa to Europe. Take it," to civilise its indigenous inhabitants. This might partly explain why in spite of his deep interest and involvement in political matters he remained strangely silent on the Algerian issue. He knew about the atrocities committed by the French Army during the French conquest of Algeria as evidenced by his diary but he never denounced them publicly. A modern reader may also feel puzzled, to say the least, at the meaning of these lines from the conclusion to Le Rhin, chapter 17, published in 1842, twelve years after French troops landed near Algiers.  However, in "Les Misérables", Hugo says the following about the conquering of Algeria:  Before being exiled he never denounced slavery, and no trace of its abolition is to be found in the 27 April 1848 entry of his detailed diary.  On the other hand, Victor Hugo fought a lifelong battle for the abolition of

Religious views.

Hugo's religious views changed radically over the course of his life. In his youth and under the influence of his mother, he identified as a Catholic and professed respect for Church hierarchy and authority. From there he became a non-practising Catholic and increasingly expressed anti-Catholic and anti-clerical views. He frequented spiritism during his exile (where he participated also in many séances conducted by Madame Delphine de Girardin) and in later years settled into a rationalist deism similar to that espoused by Voltaire. A census-taker asked Hugo in 1872 if he was a Catholic, and he replied, "No. A Freethinker".  After 1872, Hugo never lost his antipathy towards the Catholic Church. He felt the Church was indifferent to the plight of the working

Victor Hugo and music.

Although Hugo's many talents did not include exceptional musical ability, he nevertheless had a great impact on the music world through the inspiration that his works provided for composers of the 19th and 20th century. Hugo himself particularly enjoyed the music of Gluck and Weber. In, he calls the huntsman's chorus in Weber's "Euryanthe", "perhaps the most beautiful piece of music ever composed". He also greatly admired Beethoven, and rather unusually for his time, he also appreciated works by composers from earlier centuries such as Palestrina and Monteverdi.  Two famous musicians of the 19th century were friends of Hugo: Hector Berlioz and Franz Liszt. The latter played Beethoven in Hugo's home, and Hugo joked in a letter to a friend that, thanks to Liszt's piano lessons, he learned how to play a favourite song on the piano – with only one finger. Hugo also worked with composer Louise Bertin, writing the libretto for her 1836 opera "La Esmeralda", which was based on the character in "The Hunchback of Notre Dame". Although for various reasons the opera closed soon after its fifth performance and is little known today, it has enjoyed a modern revival, both in a piano/song concert version by Liszt at the 2007 and in a full orchestral version presented in July 2008 at.  On the other hand, he had low esteem for Richard Wagner, whom he described as "a man of talent coupled

Declining years and death.

When Hugo returned to Paris in 1870, the country hailed him as a national hero. He was confident that he would be offered the dictatorship, as shown by the notes he kept at the time: "Dictatorship is a crime. This is a crime I am going to commit", but he felt he had to assume that responsibility. Despite his popularity, Hugo lost his bid for re-election to the National Assembly in 1872.  Throughout his life Hugo kept believing in unstoppable humanistic progress. In his last public address on 3 August 1879 he prophesied in an over-optimistic way, "In the twentieth century war will be dead, the scaffold will be dead, hatred will be dead, frontier boundaries will be dead, dogmas will be dead; man will live."  Within a brief period, he suffered a mild stroke, his daughter Adèle was interned in an insane asylum, and his two sons died. (Adèle's biography inspired the movie "The Story of Adele H.") His wife Adèle had died in 1868.  His faithful mistress, Juliette Drouet, died in 1883, only two years before his own death. Despite his personal loss, Hugo remained committed to the cause of political change. On 30 January 1876, he was elected to the newly created Senate. This last phase of his political career was considered a failure. Hugo was a maverick and achieved little in the Senate.  Hugo suffered a mild stroke on 27 June 1878. To honour the fact that he was entering his 80th year, one of the greatest tributes to a living writer was held. The celebrations began on 25 June 1881, when Hugo was presented with a vase, the traditional gift for sovereigns. On 27 June, one of the largest parades in French history was held.  Marchers stretched from the, where the author was living,

Drawings.

Hugo produced more than 4,000 drawings. Originally pursued as a casual hobby, drawing became more important to Hugo shortly before his exile when he made the decision to stop writing to devote himself to politics. Drawing became his exclusive creative outlet between 1848 and 1851.  Hugo worked only on paper, and on a small scale; usually in dark brown or black pen-and-ink wash, sometimes with touches of white, and rarely with colour. The surviving drawings are surprisingly accomplished and "modern" in their style and execution, foreshadowing the experimental techniques of Surrealism and Abstract expressionism.  He would not hesitate to use his children's stencils, ink blots, puddles and stains, lace impressions,

Victor Hugo and women.

Wife.

Hugo married Adèle Foucher in October 1822. Despite their respective affairs, they lived together for nearly 46 years until she died in August 1868.

Mistresses.

Juliette Drouet.

From February 1833 until her death in 1883, Juliette Drouet devoted her whole life to Victor Hugo, who never married her even after his wife died in 1868. He took her on his numerous trips and she followed him in exile on Guernsey. There Hugo rented a house for her near Hauteville House, his family home. She wrote

Léonie d’Aunet.

For more than seven years, Léonie d’Aunet, who was a married woman, was involved in a love relationship with Hugo. Both were caught in adultery on 5 July 1845. Hugo, who had been a Member of the Chamber of Peers since April, avoided condemnation whereas his mistress had to spend two months in prison and six in a convent. Many years after their separation, Hugo made a point of supporting her financially.

Casual affairs.

Hugo gave free rein to his sensuality until a few weeks before his death. He sought a wide variety of women of all ages, be they courtesans, actresses, prostitutes, admirers, servants or revolutionaries like Louise Michel for sexual activity. Both a graphomaniac and erotomaniac, he systematically reported his casual affairs using his own code, as Samuel Pepys did, to make sure they would remain secret. For instance, he resorted to

Memorials.

His legacy has been honoured in many ways, including his portrait being placed on French currency. The people of Guernsey erected a statue by sculptor Jean Boucher in Candie Gardens (Saint Peter Port) to commemorate his stay in the islands. The City of Paris has preserved his residences Hauteville House, Guernsey, and, Paris, as museums. The house where he stayed in Vianden, Luxembourg, in 1871 has also become a commemorative museum.  Hugo is venerated as a saint in the Vietnamese religion of, in the front hall of the Holy See in.  The in the 16th arrondissement of Paris bears Hugo's name and links the to the vicinity of the by way of the. This square is served by a Paris Métro stop also named in his honour. In the town of there

Religious veneration.

Thanks to his contribution to mankind, his virtues, and belief in God, he is venerated as a saint in, a new religion established in Vietnam in 1926. According to religious records, he was assigned by God to lead the foreign mission as part of God's Divine

Works.

Published during Hugo's lifetime.

Poems

Victor Marie Hugo (; 7 Ventôse year X – 22 May 1885) was a French poet, novelist, and dramatist of the Romantic movement. During a literary career that spanned more than sixty years, he wrote abundantly in an exceptional variety of genres: lyrics, satires, epics, philosophical poems, epigrams, novels, history, critical essays, political speeches, funeral orations, diaries, letters public and private, and dramas in verse and prose.

维克多·马里·雨果(,,1802年-2月26日-1885年-5月22日),法国浪漫主义文学的代表人物和19世纪前期积极浪漫主义文学运动的领袖,法国文学史上卓越的作家。雨果几乎经历了19世纪法国的所有重大事变。一生创作了众多诗歌、小说、剧本、各种散文和文艺评论及政论文章。代表作有《钟楼怪人》、《九三年》、和《悲惨世界》等。在法国,雨果主要以诗集纪念,如《静观集》和《历代传说》。他创作了4000多幅画,积极参与许多社会运动,如废除死刑。