History.

Early years.

The National Hockey League was established in 1917 as the successor to the National Hockey Association (NHA). Founded in 1909, the NHA began play one year later with seven teams in Ontario and Quebec, and was one of the first major leagues in professional ice hockey. But by the NHA's eighth season, a series of disputes with Toronto Blueshirts owner Eddie Livingstone led team owners of the Montreal Canadiens, Montreal Wanderers, Ottawa Senators, and Quebec Bulldogs to hold a meeting to discuss the league's future. Realizing the NHA constitution left them unable to force Livingstone out, the four teams voted instead to suspend the NHA, and on November 26, 1917, formed the National Hockey League. Frank Calder was chosen as its first president, serving until his death in 1943.  The Bulldogs were unable to play, and the remaining owners created a new team in Toronto, the Arenas, to compete with the Canadiens, Wanderers and Senators. The first games were played on December 19, 1917. The Montreal Arena burned down in January 1918, causing the Wanderers to cease operations, and the NHL continued on as a three-team league until the Bulldogs returned

The Original Six.

The first NHL All-Star Game was held in 1934 to benefit Ace Bailey, whose career ended on a vicious hit by Eddie Shore. The second was held in 1937 in support of Howie Morenz's family when he died of a coronary embolism after breaking his leg during a game.  The Great Depression and the onset of World War II took a toll on the league. The Pirates became the Philadelphia Quakers in 1930, then folded one year later. The Senators likewise became the St. Louis Eagles in 1934, also lasting only one year. The Maroons did not survive, as they suspended operations in 1938. The Americans were suspended in 1942 due to a lack of available players,

Post-Original Six expansion.

By the mid-1960s, the desire for a network television contract in the U.S., and concerns that the Western Hockey League was planning to declare itself a major league and challenge for the Stanley Cup, spurred the league to undertake its first expansion since the 1920s. The league doubled in size to 12 teams for the 1967–68 season, adding the Los Angeles Kings, Minnesota North Stars, Philadelphia Flyers, Pittsburgh Penguins, California Seals and St. Louis Blues. Canadian fans were outraged that all six teams were placed in the United States,

Labour issues.

There have been four league-wide work stoppages in NHL history, all occurring after 1992. The first was a strike by the National Hockey League Players' Association in April 1992 which lasted for ten days, but the strike was settled quickly and all affected games were rescheduled.  A lockout at the start of the 1994–95 season forced the league to reduce the schedule from 84 games to just 48, with the teams playing only intra-conference games during the reduced season. The resulting collective bargaining agreement (CBA) was set for renegotiation in 1998 and extended to September 15, 2004.  With no new agreement in hand when the contract expired on September 15, 2004, league commissioner Gary Bettman announced a lockout of the players union and closed the league's head office. The league vowed to install what it dubbed "cost certainty" for its teams, but the Players' Association countered that the move was little more than a euphemism for a salary cap, which the union initially said it would not accept. The lockout shut down the league for 310 days, the

Player safety issues.

Player safety has become a major issue, with concussions – a result from a hard hit to the head – being the primary concern. Recent studies have shown how the consequences of concussions can last beyond player retirement. This has significant effects on the league as elite players have suffered from the aftereffects of concussions, such as Sidney Crosby being sidelined for approximately 10 and a half months, which adversely affects the league's marketability. In December 2009, Brendan Shanahan was hired to replace Colin Campbell and given

Women in the NHL.

From 1952 to 1955, Marguerite Norris served as president of the Detroit Red Wings, the first woman NHL executive and the first woman to have her name engraved on the Stanley Cup. In 1992, Manon Rheaume became the first woman to play a game in any of the major professional North American sports leagues, as a goaltender for the Tampa Bay Lightning in an NHL pre-season game against the St. Louis Blues, stopping seven of nine shots. In 2016, Dawn Braid was hired as the Arizona Coyotes' skating coach, making her the first female full-time coach in

Organizational structure.

Board of Governors.

The Board of Governors is the ruling and governing body of the National Hockey League. In this context, each team is a member of the league, and each member appoints a Governor (usually the owner of the club), and two alternates to the Board.

Executives.

The chief executive of the league is Commissioner Gary Bettman.

Teams.

The NHL consists of 31 teams, 24 of which are based in the United States and seven in Canada. The NHL divides the 31 teams into two conferences: the Eastern Conference and the Western Conference. Each conference is split into two divisions: the Eastern Conference contains 16 teams (eight per division), while the Western Conference has 15 teams (seven in the Central Division and eight in the Pacific Division). The current alignment has existed since the 2017–18 season.  The number of NHL teams held constant at 30 teams from the 2000–01 season when the Minnesota Wild and the Columbus Blue Jackets joined the league as expansion teams, until 2017. That expansion capped a period in the 1990s of rapid expansion and relocation when the NHL added nine

Game.

Each National Hockey League regulation game is 60 minutes long. The game is composed of three 20-minute periods with an intermission between periods. At the end of regulation time, the team with the most goals wins the game. If a game is tied after regulation time, overtime ensues. During the regular season, overtime is a five-minute, three-on-three sudden-death period, in which whoever scores a goal first will win the game. If the game is still tied at the end of overtime, the game enters a shootout. Three players for each team in

Hockey rink.

National Hockey League games are played on a rectangular hockey rink with rounded corners surrounded by walls and Plexiglas. It measures by in the NHL, approximately the same length but much narrower than International Ice Hockey Federation standards. The centre line divides the ice in half, and is used to judge icing violations. There are two blue lines that divide the rink roughly into thirds, delineating one neutral and two attacking zones. Near the end of

Rules.

The National Hockey League's rules are one of the two standard sets of professional ice hockey rules in the world. The rules themselves have evolved directly from the first organized indoor ice hockey game in Montreal in 1875, updated by subsequent leagues up to 1917, when the NHL adopted the existing NHA set of rules. The NHL's rules are the basis for rules governing most professional and major junior ice hockey leagues in North America. Infractions of the rules, such as offside and icing, lead to a stoppage of play and subsequent face-offs, while more serious infractions leading to penalties to the offending teams. The league also determines the specifications for playing equipment used in its games.  The league has regularly modified its rules to counter perceived imperfections in the game. The penalty shot was adopted from the Pacific Coast Hockey Association to ensure players were not being blocked from opportunities to score. For the 2005–06 season, the league changed some of the rules regarding being offside. First, the league removed the "offside pass" or "two-line pass" rule, which required a stoppage in play if a pass originating from inside a team's defending zone was completed on the offensive side of the centre line, unless the puck crossed the line before the player. Furthermore, the league reinstated the "tag-up offside" which allows an attacking player a chance to get back onside by returning to the neutral zone. The changes

Season structure.

The National Hockey League season is divided into a preseason (September and early October), a regular season (from early October through early to mid April) and a postseason (the Stanley Cup playoffs).  Teams usually hold a summer showcase for prospects in July and participate in prospect tournaments, full games that do not feature any veterans, in September. Full training camps begin in mid-to-late September, including a preseason consisting of six to eight exhibition games. Split squad games, in which parts of a team's regular season roster play separate games on the same day, are occasionally played during the preseason.  During the regular season, clubs play each other in a predefined schedule. In the regular season, each team plays 82 games: 41 games each of home and road. Eastern teams play 28 games in their own geographic division—four against each of their seven other divisional opponents—and 24 games against the eight remaining non-divisional intra-conference opponents—three games against every team in the other division of its conference. Western teams play 26 or

Entry Draft.

The annual NHL Entry Draft consists of a seven-round off-season draft held in late June. Early NHL drafts took place at the Queen Elizabeth (currently Fairmont) Hotel in Montreal. Amateur players from junior, collegiate, or European leagues are eligible to enter the Entry Draft. The selection order is determined by a combination of the standings at the end of the regular season, playoff results, and a draft lottery. The 15 teams that did not qualify for the playoffs are entered in a weighted

Trophies and awards.

Teams.

The most prestigious team award is the Stanley Cup, which is awarded to the league champion at the end of the Stanley Cup playoffs. The team that has the most points in the regular season is awarded the Presidents' Trophy.  The Montreal Canadiens are the most successful franchise in the league. Since the formation of the league in 1917, they have 25 NHL championships (three between 1917 and 1925 when the Stanley Cup was still contested in an interleague competition, twenty-two since 1926 after the Stanley Cup became the NHL's championship trophy). They also lead all teams with 24 Stanley Cup championships (one as an NHA team, twenty-three as an NHL team). Of the four major professional sports leagues in North America, the Montreal Canadiens are surpassed

Players.

There are numerous trophies that are awarded to players based on their statistics during the regular season; they include, among others, the Art Ross Trophy for the league scoring champion (goals and assists), the Maurice "Rocket" Richard Trophy for the goal-scoring leader, and the William M. Jennings Trophy for the goaltender(s) for the team with the fewest goals against them.  The other player trophies are voted on by the Professional Hockey Writers' Association or the team general managers. These individual awards are presented at a formal ceremony held in late June after the playoffs have concluded. The most prestigious individual award is the Hart Memorial Trophy which is awarded annually to the Most Valuable Player; the voting is conducted by members of the Professional Hockey Writers Association to judge the player who is the most valuable to his team during the regular season. The Vezina Trophy is awarded annually to the person deemed the best goaltender as voted on by the general managers of the teams in the NHL. The James Norris Memorial Trophy is awarded annually to the

Origin of players.

In addition to Canadian and American born and trained players, who have historically composed a large majority of NHL rosters, the NHL also draws players from an expanding pool of other nations where organized and professional hockey is played. Since the collapse of the Soviet Bloc, political/ideological restrictions on the movement of hockey players from this region have disappeared, leading to a large influx of players mostly from Czech Republic, Slovakia and Russia into the NHL. Swedes, Finns, and other Western Europeans, who were always free to move to North America, came to the league in greater numbers than before.  Many of the league's top players in recent years have come from these European

Corporate sponsors.

The NHL lists its several official corporate partners into three categories: North American Partners, USA Partners, and Canada Partners. Discover Card is the league's official credit card in the US, while competitor Visa is an official sponsor in Canada. Likewise, Tim Hortons is the league's official coffee and doughnuts chain in Canada, while Dunkin' Donuts is the NHL's sponsor in the US.  Among its North American corporate sponsors, Kraft Heinz sponsors "Kraft Hockeyville", an annual competition in which

Media coverage.

Canada.

Broadcasting rights in Canada have historically included the CBC's "Hockey Night in Canada" ("HNIC"), a Canadian tradition dating to 1952, and even prior to that on radio since the 1920s.  The current national television and digital rightsholder is Rogers Communications, under a 12-year deal valued at C$5.2 billion which began in the 2014–15 season, as the national broadcast and cable television rightsholders. National English-language coverage of the NHL is carried primarily by Rogers' Sportsnet group

United States.

Historically, the NHL has never fared well on American television in comparison to the other American professional leagues. The league's American broadcast partners have been in flux for decades, ranging from such networks as CBS, SportsChannel America, the USA Network, Fox, ABC, and ESPN.  National U.S. television rights are currently held by NBC Sports; its current 10-year, US$2 billion contract, which began in the 2011–12 season, extended and unified rights deals that were first established in the 2005–06 season, when Comcast acquired cable rights to replace ESPN, and NBC acquired broadcast television rights under a revenue-sharing agreement to replace ABC. NBC Sports Network and

NHL Network.

The league co-owns the NHL Network, a television specialty channel devoted to the NHL. Its signature show is "NHL Tonight". The NHL Network also airs live

Out-of-market packages.

The NHL operates two subscription-based services allowing access to live, out-of-market games. NHL Centre Ice in Canada and NHL Center Ice in the United States offer access to out-of-market feeds of games through a cable or satellite television provider.

International.

Outside of Canada and the United States, NHL games are broadcast across Europe, in the Middle East, in Australia, and in the Americas across Mexico, Central America, Dominican Republic, Caribbean, South America and Brazil, among others.

International competitions.

The National Hockey League has occasionally participated in international club competitions. Most of these competitions were arranged by the NHL or NHLPA. The first international club competition was held in 1976, with eight NHL teams playing against the Soviet Championship League's HC CSKA Moscow, and Krylya Sovetov Moscow. Between 1976 and 1991, the NHL, and the Soviet Championship League would hold a number of exhibition games between the two leagues known as the Super Series. No NHL club had played a Russian-based club from the end of the Super Series in 1991 to 2008, when the New York Rangers faced Metallurg Magnitogorsk in the 2008 Victoria Cup.  In addition to the Russian clubs, NHL clubs had participated in a number of international club exhibitions and competitions with various European-based clubs. The first exhibition game to feature an NHL team against a European-based team (aside from clubs based in the former Soviet Union) was in December 1977, when the New York Rangers faced Poldi Kladno of the Czechoslovak First Ice Hockey League. In the 2000s the NHL had organized four NHL Challenge series between NHL, and European clubs. From 2007 to 2011, the NHL organized exhibition games prior to the

Popularity.

The NHL is considered one of the four major professional sports leagues in North America, along with Major League Baseball, the National Football League, and the National Basketball Association. The league is very prominent in Canada, where hockey is the most popular of these four major sports as alongside CFL. Overall, hockey has the smallest total fan base of the four leagues, the smallest revenue from television, and the least sponsorship.  The NHL holds one of the most affluent fan bases. Studies by the Sports Marketing Group conducted from 1998 to 2004 show that the NHL's fan base is much more affluent than that of the PGA Tour. A study done by the Stanford Graduate School of Business in 2004, found that NHL fans in America were the most educated and affluent of the four major leagues. Further it noted that season-ticket sales were more prominent in the NHL than the other three because of the financial ability of the NHL fan to purchase them. According to Reuters in 2010, the largest demographic of NHL fans was highly sought after group males aged 18–34. The NHL estimates that half of its fan base roots for teams in outside markets. Beginning in 2008, the NHL began a shift toward using digital technology to market to fans to capitalize on this.  The debut of the Winter Classic, an outdoor regular season NHL game held on New Year's Day 2008, was a major success for the league. The game has since become an annual staple of the NHL schedule. This, along with the transition to a national "Game of the Week" and an annual "Hockey Day in America" regional coverage, all televised on NBC, has helped increase the NHL's regular season television viewership in the United States. These improvements led NBC and the cable channel Versus to sign a ten-year broadcast deal, paying US$200 million per year for both American cable and broadcast rights; the deal will lead to further increases in television coverage on the NBC channels.  This television contract has boosted viewership metrics for the NHL. The 2010 Stanley Cup playoffs saw the largest audience in the history of the sport "after a regular season that saw record-breaking business success, propelled in large part by the NHL's strategy of engaging fans through big events and robust digital offerings." This success has resulted in a 66 percent rise in NHL advertising and sponsorship revenue. Merchandise sales were up 22 percent and the number of unique visitors on the NHL.com website were up 17 percent during the playoffs after rising 29 percent in the regular season.

The National Hockey League (NHL; ) is a professional ice hockey league in North America, currently comprising 31 teams: 24 in the United States and seven in Canada. The NHL is considered to be the premier professional ice hockey league in the world, and one of the major professional sports leagues in the United States and Canada. The Stanley Cup, the oldest professional sports trophy in North America, is awarded annually to the league playoff champion at the end of each season.

National Hockey League (NHL,'– LNH, ') je profesionální soutěž v ledním hokeji, které se účastní kluby ze Spojených států amerických a Kanady. Je považována za nejprestižnější ligu světa.


History.

The lambda calculus, developed in the 1930s by Alonzo Church, is a formal system of computation built from function application. In 1937 Turing proved that the lambda calculus and Turing machines are equivalent models of computation, showing that the lambda calculus is Turing complete. Lambda calculus forms the basis of all functional programming languages. An equivalent theoretical formulation, combinatory logic, was developed by Moses Schönfinkel and Haskell Curry in the 1920s and 1930s.  Church later developed a weaker system, the simply-typed lambda calculus, which extended the lambda calculus by assigning a type to all terms. This forms the basis for statically-typed functional programming.  The first functional programming language, LISP, was developed in the late 1950s for the IBM 700/7000 series of scientific computers by John McCarthy while at Massachusetts Institute of Technology (MIT). LISP functions were defined using Church's lambda notation, extended with a label construct to allow recursive functions. Lisp first introduced many paradigmatic features of functional programming, though early Lisps were multi-paradigm languages, and incorporated support for numerous programming styles as new paradigms evolved. Later dialects, such as Scheme and Clojure, and offshoots such as Dylan and Julia, sought to simplify and rationalise Lisp around a cleanly functional core, while Common Lisp was designed to preserve and update the paradigmatic features of the numerous older dialects it replaced.  Information Processing Language (IPL), 1956, is sometimes cited as the first computer-based functional programming language. It is an assembly-style language for manipulating lists of symbols. It does have a notion of "generator", which amounts to a function that accepts a function as an argument, and, since it is an assembly-level language, code can be data, so IPL can be regarded as having higher-order functions. However, it relies heavily on mutating list structure and similar imperative features.  Kenneth E. Iverson developed APL in the early 1960s, described in his 1962 book "A Programming Language" (). APL was the primary influence on John Backus's FP. In the early 1990s, Iverson and Roger Hui created J. In the mid-1990s, Arthur Whitney, who had previously worked with Iverson, created K, which is used commercially in financial industries along with its descendant Q.  John Backus presented FP in his 1977 Turing Award lecture "Can Programming Be Liberated From the von Neumann Style? A Functional Style and its Algebra of Programs". He defines functional programs as being built up in a hierarchical way by means of "combining forms" that allow an "algebra of programs"; in modern language, this means that functional programs follow the principle of compositionality. Backus's paper popularized research into functional programming, though it emphasized function-level programming rather than the lambda-calculus style now associated with functional programming.  The 1973 language ML was created by Robin Milner at the University of Edinburgh, and David Turner developed the language SASL at the University of St Andrews. Also in Edinburgh in the 1970s, Burstall and Darlington developed the functional language NPL. NPL was based on Kleene Recursion Equations and was first introduced in their work on program transformation. Burstall, MacQueen and Sannella then incorporated the polymorphic type checking from ML to produce the language Hope. ML eventually developed into several dialects, the most common of which are now OCaml and Standard ML.  In the 1970s, Guy L. Steele and Gerald Jay Sussman developed Scheme, as described in the Lambda Papers and the 1985 textbook "Structure and Interpretation of Computer Programs". Scheme was the first dialect of lisp to use lexical scoping and to require tail-call optimization, features that encourage functional programming.  In the 1980s, Per Martin-Löf developed intuitionistic type theory (also called "constructive" type theory), which associated functional programs with constructive proofs expressed as dependent types. This led to new approaches to interactive theorem proving and has influenced the development of subsequent functional programming languages.  The lazy functional language, Miranda, developed by David Turner, initially appeared in 1985 and had a strong influence on Haskell. With Miranda being proprietary, Haskell began with a consensus in 1987 to form an open standard for functional programming research; implementation releases have been ongoing since 1990.  More recently it has found use in niches such as parametric CAD courtesy of the OpenSCAD language built on the CSG geometry framework, although its restriction on reassigning values (all values are treated as constants) has led to confusion among users who are unfamiliar with functional programming as a concept.  Functional programming continues to be used in commercial settings.

Concepts.

A number of concepts and paradigms are specific to functional programming, and generally foreign to imperative programming (including object-oriented programming). However, programming languages often cater to several programming paradigms, so programmers using "mostly imperative" languages may have utilized some of these concepts.

First-class and higher-order functions.

Higher-order functions are functions that can either take other functions as arguments or return them as results. In calculus, an example of a higher-order function is the differential operator formula_1, which returns the derivative of a function formula_2.  Higher-order functions are closely related to first-class functions in that higher-order functions and first-class functions both allow functions as arguments and results of other functions. The distinction between the two is subtle: "higher-order" describes a mathematical concept of functions that operate on other functions, while "first-class" is a computer science term for programming language entities that have no restriction on their use (thus first-class functions can appear anywhere in the program that other first-class entities like numbers can, including as arguments to other functions and as their return values).  Higher-order functions enable partial application or currying, a technique that applies a function to its arguments one at a time, with each application returning a new function that accepts the next argument. This lets a programmer succinctly express, for example, the successor function as the addition operator partially applied to the natural number one.

Pure functions.

Pure functions (or expressions) have no side effects (memory or I/O). This means that pure functions have several useful properties, many of which can be used to optimize the code:  While most compilers for imperative programming languages detect pure functions and perform common-subexpression elimination for pure function calls, they cannot always do this for pre-compiled libraries, which generally do not expose this information, thus preventing optimizations that involve those external functions. Some compilers, such as gcc, add extra keywords for a programmer to explicitly mark external functions as pure, to enable such optimizations. Fortran 95 also lets functions be designated "pure". C++11 added codice_1 keyword with similar semantics.

Recursion.

Iteration (looping) in functional languages is usually accomplished via recursion. Recursive functions invoke themselves, letting an operation be repeated until it reaches the base case. In general, recursion requires maintaining a stack, which consumes space in a linear amount to the depth of recursion. This could make recursion prohibitively expensive to use instead of imperative loops. However, a special form of recursion known as tail recursion can be recognized and optimized by a compiler into the same code used to implement iteration in imperative languages. Tail recursion optimization can be implemented by transforming the program into continuation passing style during compiling, among other approaches.  The Scheme language standard requires implementations to support proper tail recursion, meaning they must allow an unbounded number of active tail calls. Proper tail recursion is not simply an optimization; it is a language feature that assures users that they can use recursion to express a loop and doing so would be safe-for-space. Moreover, on contrary to its name, it accounts for all tail calls, not just tail recursion. While proper tail recursion is usually implemented by turning code into imperative loops, implementations might implement it in other ways. For example, CHICKEN intentionally maintains a stack and lets the stack overflows. However, when this happens, its garbage collector will claim space back, allowing an unbounded number of active tail calls even though it does not turn tail recursion into a loop.  Common patterns of recursion can be abstracted away using higher-order functions, with catamorphisms and anamorphisms (or "folds" and "unfolds") being the most obvious examples. Such recursion schemes play a role analogous to built-in control structures such as loops in imperative languages.  Most general purpose functional programming languages allow unrestricted recursion and are Turing complete, which makes the halting problem undecidable, can cause unsoundness of equational reasoning, and generally requires the introduction of inconsistency into the logic expressed by the language's type system. Some special purpose languages such as Coq allow only well-founded recursion and are strongly normalizing (nonterminating computations can be expressed only with infinite streams of values called codata). As a consequence, these languages fail to be Turing complete and expressing certain functions in them is impossible, but they can still express a wide class of interesting computations while avoiding the problems introduced by unrestricted recursion. Functional programming limited to well-founded recursion with a few other constraints is called total functional programming.

Strict versus non-strict evaluation.

Functional languages can be categorized by whether they use "strict (eager)" or "non-strict (lazy)" evaluation, concepts that refer to how function arguments are processed when an expression is being evaluated. The technical difference is in the denotational semantics of expressions containing failing or divergent computations. Under strict evaluation, the evaluation of any term containing a failing subterm fails. For example, the expression:  fails under strict evaluation because of the division by zero in the third element of the list. Under lazy evaluation, the length function returns the value 4 (i.e., the number of items in the list), since evaluating it does not attempt to evaluate the terms making up the list. In brief, strict evaluation always fully evaluates function arguments before invoking the function. Lazy evaluation does not evaluate function arguments unless their values are required to evaluate the function call itself.  The usual implementation strategy for lazy evaluation in functional languages is graph reduction. Lazy evaluation is used by default in several pure functional languages, including Miranda, Clean, and Haskell.

Type systems.

Especially since the development of Hindley–Milner type inference in the 1970s, functional programming languages have tended to use typed lambda calculus, rejecting all invalid programs at compilation time and risking false positive errors, as opposed to the untyped lambda calculus, that accepts all valid programs at compilation time and risks false negative errors, used in Lisp and its variants (such as Scheme), though they reject all invalid programs at runtime, when the information is enough to not reject valid programs. The use of algebraic datatypes makes manipulation of complex data structures convenient; the presence of strong compile-time type checking makes programs more reliable in absence of other reliability techniques like test-driven development, while type inference frees the programmer from the need to manually declare types to the compiler in most cases.  Some research-oriented functional languages such as Coq, Agda, Cayenne, and Epigram are based on intuitionistic type theory, which lets types depend on terms. Such types are called dependent types. These type systems do not have decidable type inference and are difficult to understand and program with. But dependent types can express arbitrary propositions in predicate logic. Through the Curry–Howard isomorphism, then, well-typed programs in these languages become a means of writing formal mathematical proofs from which a compiler can generate certified code. While these languages are mainly of interest in academic research (including in formalized mathematics), they have begun to be used in engineering as well. Compcert is a compiler for a subset of the C programming language that is written in Coq and formally verified.  A limited form of dependent types called generalized algebraic data types (GADT's) can be implemented in a way that provides some of the benefits of dependently typed programming while avoiding most of its inconvenience. GADT's are available in the Glasgow Haskell Compiler, in OCaml (since version 4.00) and in Scala (as "case classes"), and have been proposed as additions to other languages including Java and C#.

Referential transparency.

Functional programs do not have assignment statements, that is, the value of a variable in a functional program never changes once defined. This eliminates any chances of side effects because any variable can be replaced with its actual value at any point of execution. So, functional programs are referentially transparent.  Consider C assignment statement codice_2, this changes the value assigned to the variable codice_3. Let us say that the initial value of codice_3 was codice_5, then two consecutive evaluations of the variable codice_3 yields codice_7 and codice_8 respectively. Clearly, replacing codice_2 with either codice_7 or codice_8 gives a program with different meaning, and so the expression "is not" referentially transparent. In fact, assignment statements are never referentially transparent.  Now, consider another function such as int plusone(int x) {return x+1;} "is" transparent, as it does not implicitly change the input x and thus has no such side effects. Functional programs exclusively use this type of function and are therefore referentially transparent.

Data structures.

Purely functional data structures are often represented in a different way than their imperative counterparts. For example, the array with constant access and update times is a basic component of most imperative languages, and many imperative data-structures, such as the hash table and binary heap, are based on arrays. Arrays can be replaced by maps or random access lists, which admit purely functional implementation, but have logarithmic access and update times. Purely functional data structures have persistence, a property of keeping previous versions of the data structure unmodified. In Clojure, persistent data structures are used as functional alternatives to their imperative counterparts. Persistent vectors, for example, use trees for partial updating. Calling the insert method will result in some but not all nodes being created.

Comparison to imperative programming.

Functional programming is very different from imperative programming. The most significant differences stem from the fact that functional programming avoids side effects, which are used in imperative programming to implement state and I/O. Pure functional programming completely prevents side-effects and provides referential transparency.  Higher-order functions are rarely used in older imperative programming. A traditional imperative program might use a loop to traverse and modify a list. A functional program, on the other hand, would probably use a higher-order “map” function that takes a function and a list, generating and returning a new list by applying the function to each list item.

Side-by-side comparison of Imperative vs. Functional programming.

The following two examples (written in JavaScript) achieve the same effect - they multiply all even numbers in an array by 10 and add them all, storing the final sum in the variable "result".  Traditional Imperative Loop:  const numList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] let result = 0; for (let i = 0; i < numList.length; i++) { Functional Programming with higher-order functions:  const numList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] const result = numList

Simulating state.

There are tasks (for example, maintaining a bank account balance) that often seem most naturally implemented with state. Pure functional programming performs these tasks, and I/O tasks such as accepting user input and printing to the screen, in a different way.  The pure functional programming language Haskell implements them using monads, derived from category theory. Monads offer a way to abstract certain types of computational patterns, including (but not limited to) modeling of computations with mutable state (and other side effects such as I/O) in an imperative manner without losing purity. While existing monads may be easy to apply in a program, given appropriate templates and examples, many students find them difficult to understand conceptually, e.g., when asked to define new monads (which is sometimes needed for certain types of libraries).  Functional languages also simulate states by passing around immutable states. This can be done by making a function accept the state as one of its parameters, and return a new state together with the result, leaving the old state unchanged. Impure functional languages usually include a more direct method of managing mutable state. Clojure, for example, uses managed references that can be updated by applying pure functions to the current state. This kind of approach enables mutability while still promoting the use of pure functions as the preferred way to express computations. Alternative methods such as Hoare logic and uniqueness have been developed to track side effects in programs. Some modern research languages use effect systems to make the presence of side effects explicit.

Efficiency issues.

Functional programming languages are typically less efficient in their use of CPU and memory than imperative languages such as C and Pascal. This is related to the fact that some mutable data structures like arrays have a very straightforward implementation using present hardware (which is a highly evolved Turing machine). Flat arrays may be accessed very efficiently with deeply pipelined CPUs, prefetched efficiently through caches (with no complex pointer chasing), or handled with SIMD instructions. It is also not easy to create their equally efficient general-purpose immutable counterparts. For purely functional languages, the worst-case slowdown is logarithmic in the number of memory cells used, because mutable memory can be represented by a purely functional data structure with logarithmic access time (such as a balanced tree). However, such slowdowns are not universal. For programs that perform intensive numerical computations, functional languages such as OCaml and Clean are only slightly slower than C according to The Computer Language Benchmarks Game. For programs that handle large matrices and multidimensional databases, array functional languages (such as J and K) were designed with speed optimizations.  Immutability of data can in many cases lead to execution efficiency by allowing the compiler to make assumptions that are unsafe in an imperative language, thus increasing opportunities for inline expansion.  Lazy evaluation may also speed up the program, even asymptotically, whereas it may slow it down at most by a constant factor (however, it may introduce memory leaks if used improperly). Launchbury 1993 discusses theoretical issues related to memory leaks from lazy evaluation, and O'Sullivan "et al." 2008 give some practical advice for analyzing and fixing them. However, the most general implementations of lazy evaluation making extensive use of dereferenced code and data perform poorly on modern processors with deep pipelines and multi-level caches (where a cache miss may cost hundreds of cycles).

Functional programming in non-functional languages.

It is possible to use a functional style of programming in languages that are not traditionally considered functional languages. For example, both D and Fortran 95 explicitly support pure functions.  JavaScript, Lua and Python had first class functions from their inception. Python had support for "lambda", "map", "reduce", and "filter" in 1994, as well as closures in Python 2.2, though Python 3 relegated "reduce" to the codice_12 standard library module. First-class functions have been introduced into other mainstream languages such as PHP 5.3, Visual Basic 9, C# 3.0, C++11, and Kotlin.  In PHP, anonymous classes, closures and lambdas are fully supported. Libraries and language extensions for immutable data structures are being developed to aid programming in the functional style.  In Java, anonymous classes can sometimes be used to simulate closures; however, anonymous classes are not always proper replacements to closures because they have more limited capabilities. Java 8 supports lambda expressions as a replacement for some anonymous classes..  In C#, anonymous classes are not necessary, because closures and lambdas are fully supported. Libraries and language extensions for immutable data structures are being developed to aid programming in the functional style in C#.  Many object-oriented design patterns are expressible in functional programming terms: for example, the strategy pattern simply dictates use of a higher-order function, and the visitor pattern roughly corresponds to a catamorphism, or fold.  Similarly, the idea of immutable data from functional programming is often included in imperative programming languages, for example the tuple in Python, which is an immutable array.

Applications.

Academia.

Functional programming is an active area of research in the field of programming language theory. There are several peer-reviewed publication venues focusing on functional programming, including the International Conference on Functional Programming, the Journal of Functional Programming, and the Symposium on Trends in Functional Programming.

Industry.

Functional programming has seen use in a wide variety of industrial applications. For example, Erlang, which was developed by the Swedish company Ericsson in the late 1980s, was originally used to implement fault-tolerant telecommunications systems, but has since become popular for building a range of applications at companies such as Nortel, Facebook, Électricité de France and WhatsApp. Scheme, a dialect of Lisp, was used as the basis for several applications on early Apple Macintosh computers, and has been applied to problems such as training simulation software and telescope control. OCaml, which was introduced in the mid-1990s, has seen commercial use in areas such as financial analysis, driver verification, industrial robot programming, and static analysis of embedded software. Haskell, though initially intended as a research language, has also been applied by a range of companies, in areas such as aerospace systems, hardware design, and web programming.  Other functional programming languages that have seen use in industry include Scala, F#, Wolfram Language, Lisp, Standard ML,, DAML and Clojure.  Functional "platforms" have been popular in finance for risk analytics (particularly with the larger investment banks). Risk factors are coded as functions that form interdependent graphs (categories) to measure correlations in market shifts not unlike Gröbner basis optimizations but also for regulatory compliance such as Comprehensive Capital Analysis and Review. Given the use of OCAML or CAML variations in finance, these systems are sometimes considered related to a categorical abstract machine or CAM. Indeed, functional programming is heavily influenced by category theory.

Education.

Many universities teach or have taught functional programming as part of their undergraduate Computer Science degrees. Some use it as their introduction to programming, while others teach it after teaching imperative programming.  Outside of computer science, functional programming is being used as a method to teach problem solving, algebra and geometric concepts. It has also been used as a tool to teach classical mechanics in "Structure and Interpretation of Classical Mechanics".

In computer science, functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative programming paradigm in which function definitions are trees of expressions that each return a value, rather than a sequence of imperative statements which change the state of the program or world.

Funkcionální programování je deklarativní programovací paradigma, které chápe výpočet jako vyhodnocení matematických funkcí. Funkcionální programování má své kořeny v lambda-kalkulu, formálním systému vyvinutém v 30. letech k vyšetřování definicí funkcí, jejich aplikace a rekurze. Mnoho funkcionálních programovacích jazyků může být považováno za rozšíření lambda kalkulu.


Biography.

Early years.

Dvořák was born in Nelahozeves, near Prague, in the Austrian Empire, and was the eldest son of František Dvořák (1814–94) and his wife, Anna, née Zdeňková (1820–82). František worked as an innkeeper, a professional player of the zither, and a butcher. Anna was the daughter of Josef Zdeněk, the bailiff of the Prince of Lobkowicz. Anna and František married on 17 November 1840. Dvořák was the first of 14 children, eight of whom survived infancy. Dvořák was baptized as a Roman Catholic in the village's church of St. Andrew. Dvořák's years in Nelahozeves nurtured his strong Christian faith and the love for his Bohemian heritage that so strongly influenced his music. In 1847,

Composer and organist.

Dvořák called his String Quintet in A minor (1861) his Opus 1, and his First String Quartet (1862) his Opus 2, although the chronological Burghauser Catalogue numbers these as B.6 and B.7, showing five earlier compositions without opus numbers. In the early 1860s, Dvořák also made his first symphonic attempts, some of which he self-critically burned. The manuscript of a symphony in C minor without opus number, B.9, composed in 1865, was preserved. This symphony has come to be numbered as Dvořák's First (see under "Works"). His first composing attempts passed without critical reception or public performances. His compositions up through 1870, according to the Burghauser Catalogue either had no known premieres, or were premiered in 1888 or later. For example, the Third String Quartet, B.18, was written in about 1869 but first

International reputation.

Dvořák entered the Austrian Prize competition again in 1877, submitting his Moravian Duets and other music, possibly his Piano Concerto. He did not learn the outcome until December. Then, he received a personal letter from the music critic Eduard Hanslick, who had also been on the juries awarding the prizes. The letter not only notified Dvořák that he had again won the prize, but made known to him for the first time that Brahms and Hanslick had been on the jury. The

Reception in Britain.

Dvořák's Stabat Mater (1880) was performed and very well received at the Royal Albert Hall in London on 10 March 1883, conducted by Joseph Barnby. The success "sparked off a whole series of performances in England and the United States", a year ahead of appreciation in Germany and Austria. Dvořák was invited to visit Britain where he appeared to great acclaim in 1884. The London Philharmonic Society commissioned Dvořák to conduct concerts in London, and his performances were well received there. In response to the commission, Dvořák wrote his Symphony No. 7 and conducted its premiere at St. James's Hall on 22

1888–1891.

Despite Dvořák's newfound success, a February 1888 performance of Stabat Mater in Vienna fell victim to more anti-Czech feeling and what the composer called "destructive criticism". He heartily thanked Richter for his "courage and devoted sympathy". In 1890, influenced by Pyotr Ilyich Tchaikovsky, Dvořák also visited Russia, and conducted performances of his music in Moscow and St. Petersburg. In 1891, Dvořák received an honorary degree from the University of Cambridge, and was offered a position at the Prague Conservatory as professor of composition and instrumentation. At first he refused

United States.

From 1892 to 1895, Dvořák was the director of the National Conservatory of Music in New York City. He began at a then-staggering $15,000 annual salary. Emanuel Rubin describes the Conservatory and Dvořák's time there. The Conservatory had been founded by Jeannette Thurber, a wealthy and philanthropic woman, who made it open to women and black students as well as white men, which was unusual for the times. Dvořák's original contract provided for three hours a day of work, including teaching and conducting, six days a week, with four months’ vacation each summer. The Panic of 1893, a severe economic depression, depleted the assets of the Thurber family and other patrons of the Conservatory. In 1894 Dvořák's salary was cut

Return to Europe and last years.

Dvořák returned from the United States on 27 April 1895 with his wife and Otakar Berger, and took care to avoid spreading the news about his return. However, after a performance of "Dimitrij" at the National Theater on 19 May, Dvořák fled to the family country cottage in Vysoká. Dvořák's first love and later sister-in-law, Josefina Kaunitzová, née Čermáková, died in May 1895. He and she had maintained friendly relations over the years. After her death he revised the coda of his Cello Concerto in her memory. During Dvořák's final years, he concentrated on composing opera and chamber music. In November 1895, he resumed his professorship at the Prague Conservatory. Between 1895 and 1897, he completed his string quartets in A-flat major and G major, and also worked on the cycle of symphonic poems inspired by the collection "Kytice" by Karel Jaromír Erben. As seen in Burghauser's 1960 Catalogue, Dvořák wrote his five Symphonic Poems in 1896, but after that completed few works per year, mainly operas: "Jakobín" in 1896, nothing in 1897, only "The Devil and Kate" in 1898–99, "Rusalka" in 1900, two songs and "Recitatives" in 1900/01, and finally the

Style.

Many of Dvořák's compositions, such as the "Slavonic Dances" and his large collection of songs, were directly inspired by Czech, Moravian, and other Slavic traditional music. As the basis for his works, Dvořák frequently used Slavic folk dance forms including the skočná; the Bohemian odzemek, furiant, sousedská, and špacirka; the Polish mazurka and polonaise; the Yugoslav Kolo; and folk song forms of Slavic peoples, including the Ukrainian dumka. His 16 Slavonic Dances, Op. 46, which first brought him a wide reputation, and Op. 72, include at least one of each of these forms. He also wrote an orchestral "Polonaise" (1879). He named the third movement of his 6th Symphony as "Scherzo (Furiant)". His Dumky Trio is one of his best-known chamber

Works.

Dvořák wrote in a variety of forms: his nine symphonies generally stick to classical models, but he also worked in the newly developed form of symphonic poem. Many of his works show the influence of Czech folk music, both in terms of elements such as rhythms and melodic shapes; amongst these are the two sets of Slavonic Dances, the "Symphonic Variations", and the overwhelming majority of his songs, but echoes of such influence are also found in his major choral works. Dvořák also wrote operas (of which the best known is "Rusalka"); serenades for string orchestra and wind ensemble; chamber music (including a number of string quartets and quintets); and piano music.

Numbering.

While a large number of Dvořák's works were given opus numbers, these did not always bear a logical relationship to the order in which they were either written or published. To achieve better sales, some publishers such as N. Simrock preferred to present budding composers as being well established, by giving some relatively early works much higher opus numbers than their chronological order would merit. In other cases, Dvořák deliberately provided new works with lower opus numbers to be able to sell them outside contract obligations to other publishers. An example is the "Czech Suite" which Dvořák didn't want to sell to Simrock, and had published with Schlesinger as Op. 39 instead of Op. 52. In this way it could come about that the same opus number was given to more than one of Dvořák's works; for example the opus number 12, which was assigned, successively, to: the opera "King and Charcoal

Symphonies.

During Dvořák's life, only five of his symphonies were widely known. The first published was his sixth, dedicated to Hans Richter. After Dvořák's death, research uncovered four unpublished symphonies, of which the manuscript of the first had even been lost to the composer himself. This led to an unclear situation in which the "New World Symphony" has alternately been called the 5th, 8th and 9th. This article uses the modern numbering system, according to the order in which the symphonies were written.  With their broadly lyrical style and accessibility to the listener, Dvořák's symphonies seem to derive

Symphonic poems.

Franz Liszt had invented the form Symphonic Poem, a relatively new one, never adopted by more "conservative" Romantic composers such as Brahms. Dvořák wrote five symphonic poems, all in 1896–1897, and they have sequential opus numbers: "The Water Goblin", Op.

Choral works.

To Dvořák's main choral works belong his setting of Stabat Mater (the longest extant setting of that text), his Requiem, his setting of the Te Deum and his Mass in D major.  The Stabat Mater, Op. 58, is an extensive (c. 90 minutes) vocal-instrumental sacred work for soli (soprano, alto, tenor and bass), choir and orchestra based on the text of an old church hymn with the same name. The first inspiration for creating this piece was the death of the composer's daughter, Josefa.  Antonín Dvořák composed his Requiem in 1890, at the beginning of the peak period of his career. Dvořák was a deeply religious man, and this work reflects his faith and spirituality. The premiere of the work took place on 9 October 1891 in Birmingham, conducted by Dvořák himself, and was "very successful". It had an outstanding success in Boston 30 November 1892: "the composer was frequently applauded between numbers and given a most enthusiastic ovation at the end.". In Vienna it was greeted, belatedly, in 1901: "The Vienna performance in March 1901 was a triumph of Dvořák's music, as if the Viennese public wished thereby to make up for their earlier, sometimes

Concerti.

The critic Harold C. Schonberg wrote that Dvořák wrote "an attractive Piano Concerto in G minor with a rather ineffective piano part, a beautiful Violin Concerto in A minor, and a supreme Cello Concerto in B minor". All the concerti are in the classical three-movement form.  The Concerto for Piano and Orchestra in G minor, Op. 33 was the first of three concerti (for solo instrument and orchestra) that Dvořák composed, and it is perhaps the least known of the three.  The Concerto for Violin and Orchestra in A minor, Op. 53 was written in 1878 for the great violinist Joseph Joachim, whom Dvořák had met and admired. He finished it in 1879, but Joachim was skeptical of the work. The concerto was premiered in 1883 in Prague by the violinist František Ondříček, who also gave its first performances in Vienna and London.  The Concerto for Cello and Orchestra in B minor, Op. 104 was the last

Chamber music.

Over a period of almost 30 years, Dvořák's output of chamber music was prolific and diverse, including more than 40 works for ensembles with strings. In 1860 just after he finished his education at the Organ school, Dvořák composed his String Quintet No. 1 in A minor, Op. 1. Two more would follow, of which the String Quintet No. 2 in G major, Op. 77 from early 1875, is noteworthy for the use of a double bass. It was written for a chamber music competition sponsored by the "Umělecká beseda" (Artistic Circle), where it was unanimously awarded the prize of five ducats for the ""distinction of theme, the technical skill in polyphonic composition, the mastery of form and the knowledge of the instruments"" displayed. The String Quintet No.3 in E major, Op. 97, with a second viola added, was written near the end of his output for chamber ensemble during his American period in 1893, when he spent a summer holiday in Spillville, Iowa.  Within a year after completing his first string quintet, Dvořák completed his String Quartet No. 1 in A major, Op. 2, the first of his fourteen string quartets. For some time Dvořák was very tentative

Operas.

In a 1904 interview, Dvořák claimed that opera was 'the most suitable form for the nation'. If this nationalist sentiment was at the heart of his opera compositions, he also struggled to find a style straddling Czech traditional melody and the grand opera style of Giacomo Meyerbeer, which he experienced as lead viola player in the orchestra of Prague's Provisional Theatre between 1862 and 1871, and whose influence is very evident in his works such as "Vanda" and "Dimitrij". His later interest in

Songs.

The song cycle of 10 "Biblical Songs", Op. 99, B. 185, was written in March 1894. Around that time Dvořák was informed of the death of the famous conductor, and his close personal friend, Hans von Bülow. Just a month earlier, he had been grieved to hear that his father was near death, far away in Bohemia. Dvořák consoled himself in

Other works.

From other important works that show also the influence of Czech folk music, both in terms of rhythms and of melodic shapes, perhaps the best known examples are the two sets of Slavonic Dances, written in two series. The first book, Op. 46 (1878), is predominantly Czech in respect to the forms represented. They were created for piano duet (one piano, four hands), but Dvořák proceeded to orchestrate the entire set, completing that version the same year. The second book, Op. 72 (also composed originally for piano four hands), which came along eight years later, includes forms native to such other Slavic lands as Serbia, Poland and Ukraine, although some "merge

In popular culture.

The 1980 film "Concert at the End of Summer" is based on Dvořák's life. Dvořák was played by Josef Vinklář. The 2012 television film "The American Letters" focuses on Dvořák's love life. Dvořák is played by.  Asteroid 2055 Dvořák, discovered by Luboš Kohoutek is named in his honor.  Professional wrestling stable Imperium (NXT UK) use Dvorak's New World Symphony as their entrance music.  The melody from his "Humoresque" No. 7 was used as the theme of Slappy Squirrel in the popular American animated television show "Animaniacs".

Antonín Leopold Dvořák (, ; 8 September 1841 – 1 May 1904) was a Czech composer, one of the first to achieve worldwide recognition. Following the Romantic-era nationalist example of his predecessor Bedřich Smetana, Dvořák frequently employed rhythms and other aspects of the folk music of Moravia and his native Bohemia. Dvořák's own style has been described as "the fullest recreation of a national idiom with that of the symphonic tradition, absorbing folk influences and finding effective ways of using them".

Antonín Leopold Dvořák (8. září 1841 Nelahozeves – 1. května 1904 Praha) byl jedním z nejvýznamnějších českých hudebních skladatelů a je světově nejhranějším českým skladatelem vůbec.


Formation.

With the rise of Linux during the 1990s, Linux distributions proliferated. Since the Linux kernel and GNU were both free software, anyone could put together and market a distribution. Many industry observers feared fragmentation and wide-ranging incompatibility, similar to the UNIX wars of the early 1990s.  The first moves towards the United Linux project were made at COMDEX in November 1999. There were a number of false starts, but the participants consistently agreed that a unified Linux platform for business made sense. The key factors for success were identified early in 2000.  Starting in March and April 2002, the United Linux board put together a base technical specification, getting input from the four consortium members and their business partners and vendors.  UnitedLinux, LLC was formed May 29, 2002 and the project was announced to the world on May 30, 2002. Two legal agreements were signed by the founding members at this time, the Master Transaction Agreement (MTA) and the Joint Development Contract (JDC); the JDC was also signed by UnitedLinux, LLC. These contracts provided, in part, that intellectual property related to UnitedLinux Software (with certain exceptions) would be assigned to UnitedLinux, LLC. Further, "[e]ach member shall have a broad, royalty-free license to all intellectual property rights in the UnitedLinux Software, entitling each member to "use, copy, modify, distribute, market, advertise, sell, offer for sale, sublicense... in any manner the Software, including the rights to make derivative works of the Software, to provide access to the Source Code and/or Object Code to any third party, to incorporate the Software into other products or bundle the Software with other products for its own business purposes and any other unlimited right of exploitation"; existing open source licenses, such as the GNU General Public License, also continued to apply. Disputes were to be settled via International Chamber of Commerce (ICC) arbitration.  A first beta was released to United Linux member partners on August 14, 2002, a public beta was released on September 25, 2002 and United Linux 1.0 was released on November 19, 2002.  "For a detailed case study in what led one of the four partners to embrace the ideals of United Linux see Caldera OpenLinux."

Technical overview.

The distribution was based on SUSE Linux and the Linux Standard Base, with the plan being for SUSE to do most of the engineering work and SCO, Turbolinux and Conectiva primarily to market the distribution in their territories and markets.  It was planned that version 1.0 would take six to eight months to release, be the current version for one year and be supported for another year after the release of 2.0. Minimum technical requirements were:

Ending.

On January 20, 2004, SCO filed a lawsuit, against Novell, the then-current owner of SuSE.  The end of United Linux was announced in a Novell press conference on January 22, 2004 by Richard Seibt, president of the SUSE division. The stated reason was that the SCO v. IBM lawsuit and The SCO Group's public attacks on Linux had made the alliance unworkable.  It emerged that no real work had been done on United Linux since soon after SCO v. IBM had started, and that SUSE had ceased active participation around this time. The last United Linux announcements were of Oracle Corporation support for it on 13 March 2003, and of AMD64 CPU support on 22 April 2003.  While some have reported that UnitedLinux ended, in fact the group did not gain consensus to dissolve the partnership and the legal entity remains in effect.  The SCO v. Novell complaint was amended on February 3, 2006 to add copyright infringement claims, relating to Novell's distribution of SuSE Linux. Novell responded on April 10 by filing a Request for Arbitration with the ICC, and asking that SCO's claims be stayed in the district court. They argued in the Request that through the MTA and JDC, "the UnitedLinux members agreed that each member would have an irrevocable, perpetual, and worldwide license to use and unlimitedly exploit any intellectual property rights of the other members in the UnitedLinux Software, which would be transferred to the LLC for this very purpose." Novell's motion to stay was granted in part, for those of SCO's claims relating to SuSE.  On September 14, 2007, SCO filed for bankruptcy, and on November 13, the court ruled at SCO's request that the arbitration was automatically stayed.  SuSE filed a motion to lift this stay on November 10, 2009. However, SCO objected on December 15, and SUSE's motion was denied on January 15, 2010.

United Linux was an attempt by a consortium of Linux distributors to create a common base distribution for enterprise use, so as to minimize duplication of engineering effort and form an effective competitor to Red Hat. The founding members of United Linux were SUSE, Turbolinux, Conectiva (now merged with "MandrakeSoft" to form Mandriva) and Caldera International (later renamed to The SCO Group). The consortium was announced on May 30, 2002. The end of the project was announced on January 22, 2004.

United Linux byl pokus konsorcia distributorů Linuxu vytvořit jednotný základ distribucí pro firemní použití, jakož i minimalizovat duplicitu ve vývoji distribucí a vytvořit výkonnou konkurenci Red Hatu. Zakládajícími členy byli SUSE, Turbolinux, Conectiva ad SCO (dříve "Caldera Systems"). Vznik konsorcia byl oznámen 30. května 2002 a zánik 22. ledna 2004.


Definitions.

Space opera is defined as an adventure science-fiction story.  The term "space opera" was coined in 1941 by fan writer and author Wilson Tucker as a pejorative term in an article in issue 36 of "Le Zombie", a science fiction fanzine. At the time, serial radio dramas in the United States had become popularly known as soap operas because many were sponsored by soap manufacturers. The term "horse opera" had also come into use to describe formulaic Western films. Tucker defined space opera as the science fiction equivalent: a "hacky, grinding, stinking, outworn, spaceship yarn". Fans and critics have noted that the plots of space operas have sometimes been taken from horse operas and simply translated into an outer space environment, as famously parodied on the back cover of the first issue of "Galaxy Science Fiction". During the late 1920s and early 1930s, when the stories were printed in science-fiction magazines, they were often referred to as "super-science epics".  Beginning in the 1960s, and widely accepted by the 1970s, the space opera was redefined, following Brian Aldiss' definition in "Space Opera" (1974) as – as paraphrased by Hartwell and Cramer – "the good old stuff". Yet soon after his redefinition, it began to be challenged, for example, by the editorial practice and marketing of Judy-Lynn del Rey and in the reviews of her husband and colleague Lester del Rey. In particular, they disputed the claims that space operas were obsolete, and Del Rey Books labeled reissues of earlier work of Leigh Brackett as space opera. By the early 1980s, space operas were again redefined, and the label was attached to major popular culture works such as "Star Wars". Only in the early 1990s did the term space opera begin to be recognized as a legitimate genre of science fiction. Hartwell and Cramer define space opera as:

History.

Early works which preceded the subgenre contained many elements of what would become space opera. They are today referred to as proto-space opera. Early proto-space opera was written by several 19th century French authors, for example, "Les Posthumes" (1802) by Nicolas-Edme Rétif, "Star ou Psi de Cassiopée: Histoire Merveilleuse de l’un des Mondes de l’Espace" (1854) by C. I. Defontenay and "Lumen" (1872) by Camille Flammarion. Not widely popular, proto-space operas were nevertheless occasionally written during the late Victorian and Edwardian science-fiction era. Examples may be found in the works of Percy Greg, Garrett P. Serviss, George Griffith, and Robert Cromie. One critic cites Robert William Cole's "" as the first space opera. The novel depicts an interstellar conflict between solar men of Earth and a fierce humanoid race headquartered on Sirius. However, the idea for the novel arises out of a nationalistic genre of fiction popular from 1880 to 1914 called future-war fiction.  Despite this seemingly early beginning, it was not until the late 1920s that the space opera proper began to appear regularly in pulp magazines such as "Amazing Stories". In film, the genre probably began with the 1918 Danish film, "Himmelskibet". Unlike earlier stories of space adventure, which either related the invasion of Earth by extraterrestrials, or concentrated on the invention of a space vehicle by a genius inventor, pure space opera simply took space travel for granted (usually by setting the story in the far future), skipped the preliminaries, and launched straight into tales of derring-do among the stars. Early stories of this type include J. Schlossel's "Invaders from Outside" ("Weird Tales", January 1925), "The Second Swarm" ("Amazing Stories Quarterly", spring 1928) and "The Star Stealers" ("Weird Tales", February 1929), Ray Cummings' "Tarrano the Conqueror" (1925), and Edmond Hamilton's "Across Space" (1926) and "Crashing Suns" ("Weird Tales", August–September 1928). Similar stories by other writers followed through 1929 and 1930. By 1931, the space opera was well established as a major subgenre of science fiction.  However, the author cited most often as the true father of the genre is E. E. "Doc" Smith. His first published work, "The Skylark of Space" ("Amazing Stories", August–October 1928), written in collaboration with Lee Hawkins Garby, is often called the first great space opera. It merges the traditional tale of a scientist inventing a space-drive with planetary romance in the style of Edgar Rice Burroughs. Smith's later "Lensman" series and the works of Edmond Hamilton, John W. Campbell, and Jack Williamson in the 1930s and 1940s were popular with readers and much imitated by other writers. By the early 1940s, the repetitiousness and extravagance of some of these stories led to objections from some fans and the return of the term in its original and pejorative sense.  Eventually, though, a fondness for the best examples of the genre led to a re-evaluation of the term and a resurrection of the subgenre's traditions. Writers such as Poul Anderson and Gordon R. Dickson had kept the large-scale space adventure form alive through the 1950s, followed by writers like M. John Harrison and C. J. Cherryh in the 1970s. By this time, "space opera" was for many readers no longer a term of insult but a simple description of a particular kind of science fiction adventure story.  According to author Paul J. McAuley, a number of mostly British writers began to reinvent space opera in the 1970s (although most non-British critics tend to dispute the British claim to dominance in the new space opera arena). Significant events in this process include the publication of M. John Harrison's "The Centauri Device" in 1975 and a "call to arms" editorial by David Pringle and Colin Greenland in the Summer 1984 issue of "Interzone"; and the financial success of "Star Wars", which follows some traditional space opera conventions. This "new space opera", which evolved around the same time cyberpunk emerged and was influenced by it, is darker, moves away from the "triumph of mankind" template of older space opera, involves newer technologies, and has stronger characterization than the space opera of old. While it does retain the interstellar scale and scope of traditional space opera, it can also be scientifically rigorous.  The new space opera was a reaction against the old. New space opera proponents claim that the genre centers on character development, fine writing, high literary standards, verisimilitude, and a moral exploration of contemporary social issues. McAuley and Michael Levy identify Iain M. Banks, Stephen Baxter, M. John Harrison, Alastair Reynolds, McAuley himself, Ken MacLeod, Peter F. Hamilton, Ann Leckie, and Justina Robson as the most-notable practitioners of the new space opera. One of the most notable publishers Baen Books specialises in space opera and military science fiction, publishing many of the aforementioned authors, who have won Hugo Awards.

Definitions by contrast, concurrence and comparisons.

Some critics distinguish between space opera and planetary romance. Both feature adventures in exotic settings, but space opera emphasizes space travel, while planetary romances focus on alien worlds. In this view, the Martian, Venusian, and lunar-setting stories of Edgar Rice Burroughs would be planetary romances (and among the earliest), as would be Leigh Brackett's Burroughs-influenced "Eric John Stark" stories.  Space opera can be contrasted with "hard science fiction", in which the emphasis is on the effects of technological progress and inventions, and where the settings are carefully worked out to obey the laws of physics, cosmology, mathematics, and biology. Examples are seen in the works of Alastair Reynolds or the movie "The Last Starfighter". At other times, space opera can concur with hard science fiction and differ from soft science fiction by instead focusing on scientific accuracy such as "The Risen Empire" by Scott Westerfeld. Other space opera works may be defined as a balance between both or simultaneously hard and soft science fiction such as the "Dune" prequel series by Kevin J. Anderson and Brian Herbert or the "Star Wars" series created by George Lucas.  Several subsets of space opera overlap with military science fiction, concentrating on large-scale space battles with futuristic weapons. In such stories, the military tone and weapon system technology may be taken very seriously. At one extreme, the genre is used to speculate about future wars involving space travel, or the effects of such a war on humans; at the other, it consists of the use of military fiction plots with superficial science-fiction trappings. The term "military space opera" is occasionally used to denote this subgenre, as used for example by critic Sylvia Kelso when describing Lois McMaster Bujold's "Vorkosigan Saga".

Parodies.

Space opera parodies are often themselves examples of space opera.  Fredric Brown's "What Mad Universe" has as its protagonist a sober-headed science fiction magazine editor who suddenly finds himself transported to an alternative history timeline where all the space opera elements (a larger-than-life space hero fighting evil aliens who are totally bent on humanity's destruction, etc.) are concrete, daily life realities.  Harry Harrison's "Bill, the Galactic Hero" and "Star Smashers of the Galaxy Rangers" parody the conventions of classic space opera.  Jack Vance's "Space Opera" has an opera company go on tour into space.  The comedy film "Spaceballs", directed and co-written by Mel Brooks, is a science fiction parody with many space opera characteristics. The anime "Space Dandy" by Studio Bones often parodies other science fiction works and the space opera subgenre.

Space opera is a subgenre of science fiction that emphasizes space warfare, melodramatic adventure, interplanetary battles, chivalric romance, and risk-taking. Set mainly or entirely in outer space, it usually involves conflict between opponents possessing advanced abilities, futuristic weapons, and other sophisticated technology. The term has no relation to music, as in a traditional opera, but is instead a play on the terms "soap opera", a melodramatic television series, and "horse opera", which was coined during the 1930s to indicate a clichéd and formulaic Western movie. Space operas emerged in the 1930s and continue to be produced in literature, film, comics, television, and video games.

Vesmírná opera nebo Space opera je žánr fantastiky úzce spojený se science fiction. Dílo spadající do této kategorie obvykle zahrnuje romantické dobrodružství, mezihvězdné cestování, vesmírné bitvy a příběh točící se kolem mezihvězdného konfliktu a osobních dramat.


History.

Windows 2000 is a continuation of the Microsoft Windows NT family of operating systems, replacing Windows NT 4.0. The original name for the operating system was Windows NT 5.0 and the first beta was released in September 1997, followed by Beta 2 in August 1998. On October 27, 1998, Microsoft announced that the name of the final version of the operating system would be Windows 2000, a name which referred to its projected release date. Windows 2000 Beta 3 was released in January 1999. NT 5.0 Beta 1 was similar to NT 4.0, including a very similarly themed logo. NT 5.0 Beta 2 introduced a new'mini' boot screen, and removed the 'dark space' theme in the logo. The NT 5.0 betas had very long startup and shutdown sounds, though these were changed in the early Windows 2000 beta, but during Beta 3, a new piano-made startup and shutdown sounds were made, featured in the final version as well as in Windows Me. The new login prompt from the final version made its first appearance in Beta 3 build 1946 (the first build of Beta 3). The new, updated icons (for "My Computer", "Recycle Bin" etc.) first appeared in Beta 3 build 1976. The Windows 2000 boot screen in the final version first appeared in Beta 3 build 1994. Windows 2000 did not have a codename because, according to Dave Thompson of Windows NT team, "Jim Allchin didn't like codenames".  Windows 2000 Service Pack 1 was codenamed "Asteroid" and Windows 2000 64-bit was codenamed "Janus." During development, there was a build for the Alpha which was abandoned some time after RC1 after Compaq announced they had dropped support for Windows

New and updated features.

Windows 2000 introduced many of the new features of Windows 98 and Windows 98 SE into the NT line, such as the Windows Desktop Update, Internet Explorer 5 (Internet Explorer 6, which followed in 2001, is also available for Windows 2000), Outlook Express, NetMeeting, FAT32 support, Windows Driver Model, Internet Connection Sharing, Windows Media Player, WebDAV support etc. Certain new features are common across all editions of Windows 2000, among them NTFS 3.0, the Microsoft Management Console (MMC), UDF support, the Encrypting File System (EFS), Logical Disk Manager, Image Color Management 2.0, support for PostScript 3-based printers, OpenType codice_1 and Type 1 PostScript codice_2 font support (including a new font—Palatino Linotype—to showcase some OpenType features), the Data protection API (DPAPI), an LDAP/Active Directory-enabled Address Book, usability enhancements and multi-language and locale support. Windows 2000 also introduced USB device class drivers for USB printers, Mass storage class devices, and improved FireWire SBP-2 support for printers and scanners, along with a "Safe removal" applet for storage devices. Windows 2000 is also the first Windows version to support hibernation at the operating system level (OS-controlled ACPI S4 sleep state) unlike Windows 98 which required special drivers from the hardware manufacturer or driver developer.  A new capability designed to protect critical system files called Windows File Protection was introduced. This protects critical Windows system files by preventing programs other than Microsoft's operating system update mechanisms such as the "Package Installer", Windows Installer and other update components from modifying them. The System File Checker utility provides users the ability to perform a manual scan of the integrity of all protected system files, and optionally repair them, either by restoring from a cache stored in a separate "DLLCACHE" directory, or from the original install media.  Microsoft recognized that a serious error (a Blue Screen of Death) or a stop error could cause problems for servers that needed to be constantly running and so provided a system setting that would allow the server to automatically reboot when a stop error occurred. Also included is an option to dump any of the first 64 KB of memory to disk (the smallest amount of memory that is useful for debugging purposes, also known as a minidump), a dump of only the kernel's memory, or a dump of the entire contents of memory to disk, as well as write that this event happened to the Windows 2000 event log. In order to improve performance on servers running Windows 2000, Microsoft gave administrators the choice of optimizing the operating system's memory and processor usage patterns for background services or for applications. Windows 2000 also introduced core system administration and management features as the Windows Installer, Windows Management Instrumentation and Event Tracing for Windows (ETW) into the operating system.

Deployment.

Windows 2000 can be deployed to a site via various methods. It can be installed onto servers via traditional media (such as CD) or via distribution folders that reside on a shared folder. Installations can be attended or unattended. During a manual installation, the administrator must specify configuration options. Unattended installations are scripted via an answer file, or a predefined script in the form of an INI file that has all the options filled in. An answer file can be created manually or using the graphical "Setup manager". The Winnt.exe or Winnt32.exe program then uses that answer file to automate the installation. Unattended installations can be performed via a bootable CD, using Microsoft Systems Management Server (SMS), via the System Preparation Tool (Sysprep), via the Winnt32.exe program using the /syspart switch or via Remote Installation Services (RIS). The ability to slipstream a service pack into the original operating system setup files is also introduced in Windows 2000.  The Sysprep method is started on a standardized reference computer – though the hardware need not be similar – and it copies the required installation files from the reference computer to the target computers. The hard drive does not need to be in the target computer and may be swapped out to it at any time, with the hardware configured later. The Winnt.exe program must also be passed a /unattend switch that points to a valid answer

Editions.

Microsoft released various editions of Windows 2000 for different markets and business needs: Professional, Server, Advanced Server and Datacenter Server. Each was packaged separately. Windows 2000 Professional was designed as the desktop operating system for businesses and power users. It is the client version of Windows 2000. It offers greater security and stability than many of the previous Windows desktop operating systems. It supports up to two processors, and can address up to 4GB of RAM. The system requirements are a Pentium processor (or equivalent) of 133MHz or greater, at least 32MB of RAM, 650MB of hard drive space, and a CD-ROM drive (recommended: Pentium II, 128MB of RAM, 2GB of hard drive space, and CD-ROM drive). Windows 2000 Server shares the same user interface with Windows 2000 Professional, but contains additional components for the computer to perform server roles and run infrastructure and application software. A significant new component introduced in the server versions is Active Directory, which is an enterprise-wide directory service based on LDAP (Lightweight Directory Access Protocol). Additionally, Microsoft integrated Kerberos network authentication, replacing the often-criticised NTLM (NT LAN Manager) authentication system used in previous versions. This also provided a purely transitive-trust relationship between Windows 2000 domains in a "forest" (a collection of one

Service packs.

Windows 2000 has received four full service packs and one rollup update package following SP4, which is the last service pack. Microsoft phased out all development of its Java Virtual Machine (JVM) from Windows 2000 in SP3. Internet Explorer 5.01 has also been upgraded to the corresponding service pack level.  Microsoft had originally intended to release a fifth service pack

Upgradeability.

Several of Windows 2000's components are upgradable to newer

Security.

During the Windows 2000 period, the nature of attacks on Windows servers changed: more attacks came from remote sources via the Internet. This has led to an overwhelming number of malicious programs exploiting the IIS services – specifically a notorious buffer overflow tendency. This tendency is not operating-system-version specific, but rather configuration-specific: it depends on the services that are enabled. Following this, a common complaint is that "by default, Windows 2000 installations contain numerous potential security problems. Many unneeded services are installed and enabled, and there is no active local security policy." In addition to insecure defaults, according to the SANS Institute, the most common flaws discovered are remotely exploitable buffer overflow vulnerabilities. Other criticized flaws include the use of vulnerable encryption techniques.  Code Red and Code Red II were famous (and much discussed) worms that exploited vulnerabilities of the Windows

Support lifecycle.

Windows 2000 was superseded by newer Microsoft operating systems: Windows 2000 Server products by Windows Server 2003, and Windows 2000 Professional by Windows XP Professional.  The Windows 2000 family of operating systems moved from mainstream support to the extended support phase on June 30, 2005. Microsoft says that this marks the progression of Windows 2000 through the Windows lifecycle policy. Under mainstream support, Microsoft freely provides design changes if any, service packs and non-security related updates in addition to security updates, whereas in extended support, service packs are not provided and non-security updates require contacting the support personnel by e-mail or phone. Under the extended support phase, Microsoft continued to provide critical security updates every month for all components of Windows 2000 (including Internet Explorer 5.0 SP4) and paid per-incident support for technical issues. Because of Windows 2000's age, updated versions of components such as Windows Media Player 11 and Internet Explorer 7 have not been released for it. In the case of Internet Explorer, Microsoft said in 2005 that, "some of the security work in IE 7 relies on operating system

Total cost of ownership.

In October 2002, Microsoft commissioned IDC to determine the total cost of ownership (TCO) for enterprise applications on Windows 2000 versus the TCO of the same applications on Linux. IDC's report is based on telephone interviews of IT executives and managers of 104 North American companies in which they determined what they were using for a specific workload for file, print, security and networking services. IDC determined that the four areas where Windows 2000 had a better TCO than Linux – over a period of five years for an average organization of 100 employees – were file, print, network infrastructure and security infrastructure. They determined, however, that Linux had a better TCO than Windows 2000 for web serving. The report also found that the greatest cost was not in the procurement of software and hardware, but in staffing costs and downtime. While the report applied a 40% productivity factor during IT infrastructure downtime, recognizing that employees are not entirely unproductive, it did not consider the impact of downtime on the profitability of the business. The report stated that Linux servers had less unplanned downtime than Windows 2000 servers. It found that most Linux servers ran less workload per server than Windows 2000 servers and also that none of the businesses interviewed used 4-way SMP Linux computers. The report also did not take into account specific application servers – servers that need low maintenance and are provided by a specific vendor. The report did emphasize that TCO was only one factor in considering whether to use a particular IT platform, and also noted that as management and server software improved and became better packaged the overall picture shown could change.

Windows 2000 is a business-oriented operating system that was produced by Microsoft in the United States and was released as part of the Windows NT family of operating systems. It was succeeded by Windows XP in 2001, releasing to manufacturing on December 15, 1999 and being officially released to retail on February 17, 2000. It is the successor to Windows NT 4.0.

Windows 2000 je název několika variant operačního systému z řady Windows NT vytvořeného firmou Microsoft uvedených na trh 17. února 2000. Jeho podpora byla ukončena v červenci roku 2010. Jeho předchůdcem byl systém Windows NT 4.0 a nástupcem systém Windows XP pro desktop a Windows Server 2003 jako server. Windows 2000 byly zamýšleny jako firemní systém, zatímco Windows Me, které byly uvolněny sedm měsíců po Windows 2000, byly zamýšleny jako systém pro domácí použití (Windows Me patří do starší řady Microsoft Windows pro DOS).