History.

In 1955, Soviet computer scientist Kateryna Yushchenko invented the Address programming language that made possible indirect addressing and addresses of the highest rank – analogous to pointers. This language was widely used on the Soviet Union computers. However, it was unknown outside the Soviet Union and usually Harold Lawson is credited with the invention, in 1964, of the

Formal description.

In computer science, a pointer is a kind of reference.  A "data primitive" (or just "primitive") is any datum that can be read from or written to computer memory using one memory access (for instance, both a "byte" and a "word" are primitives).  A "data aggregate" (or just "aggregate") is a group of primitives that are logically contiguous in memory and that are viewed collectively as one datum (for instance, an aggregate could be 3 logically contiguous bytes, the values of which represent the 3 coordinates of a point in space). When an aggregate is entirely composed of the same type of primitive, the aggregate may be called an "array"; in a sense, a multi-byte "word" primitive is an array of bytes, and some programs use words in this way.  In the context of these definitions, a "byte" is the smallest primitive;

Use in data structures.

When setting up data structures like lists, queues and trees, it is necessary to have pointers to help manage how the structure is implemented and controlled. Typical examples of pointers are start pointers, end pointers, and stack pointers. These pointers can either be absolute (the actual physical address or a virtual address in virtual memory) or relative (an offset from an absolute start address ("base") that typically uses fewer bits than a full address, but will usually require one additional arithmetic operation to resolve).  Relative addresses are a form of manual memory segmentation, and share many of its advantages and disadvantages. A two-byte offset, containing a 16-bit, unsigned integer,

Use in control tables.

Control tables that are used to control program flow usually make extensive use of pointers. The pointers, usually embedded in a table entry, may, for instance, be used to hold the entry points to subroutines to be executed, based on certain conditions defined in the same table entry. The pointers can however be simply

Architectural roots.

Pointers are a very thin abstraction on top of the addressing capabilities provided by most modern architectures. In the simplest scheme, an "address", or a numeric index, is assigned to each unit of memory in the system, where the unit is typically either a byte or a word – depending on whether the architecture is byte-addressable or word-addressable – effectively transforming all of memory into a very large array. The system would then also provide an operation to retrieve the value stored in the memory unit at a given address (usually utilizing the machine's general purpose registers).  In the usual case, a pointer is large enough to hold more addresses than there are units of memory in the system. This introduces the possibility that a program may attempt to access an address which corresponds to no unit of memory, either because not enough memory is installed (i.e. beyond the range of available memory) or the architecture does not support such addresses. The first case may, in certain platforms such as the

Uses.

Pointers are directly supported without restrictions in languages such as PL/I, C, C++, Pascal, FreeBASIC, and implicitly in most assembly languages. They are primarily used for constructing references, which in turn are fundamental to constructing nearly all data structures, as well as in passing data between different parts of a program.  In functional programming languages that rely heavily on lists, data references are managed abstractly by using primitive constructs like cons and the corresponding elements car and cdr, which can be thought of as specialised pointers to the first and second components of a cons-cell. This gives rise to some of the idiomatic "flavour" of functional programming. By structuring data in such cons-lists, these languages facilitate recursive means for building and processing data—for example, by recursively accessing the head and tail elements of lists of lists; e.g. "taking the car of the cdr of the cdr". By contrast, memory management based on pointer dereferencing in some approximation of an array of memory addresses facilitates treating variables as slots into which data can be assigned imperatively.  When dealing with arrays, the critical lookup operation typically involves a stage called "address calculation" which involves constructing a pointer to the desired data element in the array. In other data structures, such as linked lists, pointers are used as references to explicitly tie one piece of the structure to another.  Pointers are used to pass parameters by reference. This is useful if the programmer wants a function's modifications to a parameter to be visible to the function's caller. This is also useful for returning multiple values from a function.  Pointers can also be used to allocate and deallocate dynamic variables and arrays in memory. Since a variable will often become redundant after it has served its purpose, it is a waste of memory to keep it, and therefore it is good practice to deallocate it (using the original pointer reference) when it is no longer needed. Failure to do so may result in a "memory leak" (where available free memory gradually, or in severe cases rapidly, diminishes because of an accumulation of numerous redundant memory blocks).

C pointers.

The basic syntax to define a pointer is:  int *ptr;  This declares codice_1 as the identifier of an object of the following type: This is usually stated more succinctly as "codice_1 is a pointer to codice_2."  Because the C language does not specify an implicit initialization for objects of automatic storage duration, care should often be taken to ensure that the address to which codice_1 points is valid; this is why it is sometimes suggested that a pointer be explicitly initialized to the null pointer value, which is traditionally specified in C with the standardized macro codice_6:  int *ptr = NULL;  Dereferencing a null pointer in C produces undefined behavior, which could be catastrophic. However, most implementations simply halt execution of the program in question, usually with a segmentation fault.  However, initializing pointers unnecessarily could hinder program analysis, thereby hiding bugs.  In any case, once a pointer has

C arrays.

In C, array indexing is formally defined in terms of pointer arithmetic; that is, the language specification requires that codice_22 be equivalent to codice_23. Thus in C, arrays can be thought of as pointers to consecutive areas of memory (with no gaps), and the syntax for accessing arrays is identical for that which can be used to dereference pointers. For example, an array codice_24 can be declared and used in the following manner: int array[5]; /* Declares 5 contiguous integers */ int *ptr = array; /* Arrays can be used as pointers */ ptr[0] = 1; /* Pointers can be indexed with array syntax */ array[2] = 4; /* Subscript operator is commutative */ This allocates a block of five integers and names the block codice_24, which acts

C linked list.

Below is an example definition of a linked list in C. /* the empty linked list is represented by NULL  struct link {  This pointer-recursive definition is essentially the same as the reference-recursive definition from the Haskell programming

Pass-by-address using pointers.

Pointers can be used to pass variables by their address, allowing their value to be changed. For example, consider the following C code: /* a copy of the int n

Dynamic memory allocation.

In some programs, the required memory depends on what "the user" may enter. In such cases the programmer needs to allocate memory dynamically. This is done by allocating memory at the "heap" rather than on the "stack", where variables usually are stored (variables can also be stored in the CPU registers, but that's another matter). Dynamic memory allocation can only be made through pointers, and names (like with common variables) can't be given.  Pointers are used to store and manage the addresses of dynamically allocated blocks of memory. Such blocks are used to store data objects or arrays of objects. Most structured and object-oriented languages provide

Memory-mapped hardware.

On some computing architectures, pointers can be used to directly manipulate memory or memory-mapped devices.  Assigning addresses to pointers is an invaluable tool when programming microcontrollers. Below is a simple example declaring a pointer of type int and initialising it to a hexadecimal address in this example the constant 0x7FFF: int *hardware_address = (int *)0x7FFF; In the mid

Typed pointers and casting.

In many languages, pointers have the additional restriction that the object they point to has a specific type. For example, a pointer may be declared to point to an integer; the language will then attempt to prevent the programmer from pointing it to objects which are not integers, such as floating-point numbers, eliminating some errors.  For example, in C int *money; char *bags; codice_51 would be an integer pointer and codice_52 would be a char pointer. The following would yield a compiler warning of "assignment from incompatible pointer type" under GCC bags = money; because codice_51 and codice_52 were declared with different types. To suppress the compiler warning, it must be made explicit that you do indeed wish to make the assignment by typecasting it bags = (char *)money; which says to cast the integer pointer of codice_51 to a char pointer and assign to codice_52.  A 2005 draft of the C standard requires that casting a pointer derived from one type to

Making pointers safer.

As a pointer allows a program to attempt to access an object that may not be defined, pointers can be the origin of a variety of programming errors. However, the usefulness of pointers is so great that it can be difficult to perform programming tasks without them. Consequently, many languages have created constructs designed to provide some of the useful features of pointers without some of their pitfalls, also sometimes referred to as "pointer hazards". In this context, pointers that directly address memory (as used in this article) are referred to as s, by contrast with smart pointers or other variants.  One major problem with pointers is that as long as they can be directly manipulated as a number, they can be made to point to unused addresses or to data which is being used for other purposes. Many languages, including most functional programming languages and recent imperative languages like Java, replace pointers with a more opaque type of reference, typically referred to as simply a "reference", which can only be used to refer to objects and

Null pointer.

A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent

Autorelative pointer.

An autorelative pointer is a pointer whose value is interpreted as an offset from the address of the pointer itself; thus, if a data structure has an autorelative pointer member that points to some portion

Based pointer.

A based pointer is a pointer whose value is an offset from the value of another

Multiple indirection.

In some languages, a pointer can reference another pointer, requiring multiple dereference operations to get to the original value. While each level of indirection may add a performance cost, it is sometimes necessary in order to provide correct behavior for complex data structures. For example, in C it is typical to define a linked list in terms of an element that contains a pointer to the next element of the list: struct element {  struct element *head = NULL; This implementation uses a pointer to the first element in the list as a surrogate for the entire list. If a new value is added to the beginning of the list, codice_63 has to be changed to point

Function pointer.

In some languages, a pointer can reference executable code, i.e., it can point to a function, method, or procedure. A function pointer will store the address of a function to

Dangling pointer.

A dangling pointer is a pointer that does not point to a valid object and consequently may make a program crash or behave oddly. In the Pascal or C programming languages, pointers that

Back pointer.

In doubly linked lists or tree structures, a back pointer held on an element 'points

Wild branch.

Where a pointer is used as the address of the entry point to a program or start of a function which doesn't return anything and is also either uninitialized or corrupted, if a call or jump is nevertheless made to this address, a "wild branch" is said to have occurred. The consequences are usually unpredictable and the error may present itself in several different

Simulation using an array index.

It is possible to simulate pointer behavior using an index to an (normally one-dimensional) array.  Primarily for languages which do not support pointers explicitly but "do" support arrays, the array can be thought of and processed as if it were the entire memory range (within the scope of the particular array) and any index to it can be thought of as equivalent to a general purpose register in assembly language (that points to the individual bytes but whose actual value is relative to the start of the array, not its absolute address in memory). Assuming the array is, say, a contiguous 16 megabyte character data structure, individual bytes (or

Support in various programming languages.

Ada.

Ada is a strongly typed language where all pointers are typed and only safe type conversions are permitted. All pointers are by default initialized to codice_73, and any attempt to access data through

BASIC.

Several old versions of BASIC for the Windows platform had support for STRPTR() to return the address of a string, and for VARPTR() to return the address of a variable. Visual Basic 5 also had support for OBJPTR() to return the address of an object interface, and for an ADDRESSOF operator to return the address of a function. The types of all of these are integers,

C and C++.

In C and C++ pointers are variables that store addresses and can be "null". Each pointer has a type it points to, but one can freely cast between pointer types (but not between a function pointer and an object pointer). A special pointer type called the “void pointer” allows pointing to any (non-function) object, but is limited by the fact that it cannot be dereferenced directly (it shall be cast). The address itself can often be directly manipulated by casting a pointer to and from an integral type of sufficient size, though the results are implementation-defined and may indeed cause undefined behavior; while earlier C standards did not have an integral type that was guaranteed to be large enough, C99 specifies the codice_81 "typedef name" defined in codice_82, but an implementation need not provide it.  C++ fully supports C pointers and C typecasting. It also supports a new group of typecasting operators to help catch some unintended dangerous casts at compile-time. Since C++11, the C++ standard library also provides smart pointers (codice_83, codice_84 and codice_85) which can be used in some situations as a safer alternative to primitive C pointers. C++ also supports another form of reference, quite different from a pointer, called simply a "reference" or "reference type".  Pointer arithmetic, that is, the ability to modify a pointer's target address with arithmetic operations (as well as magnitude comparisons), is restricted by the language standard to remain within the bounds of a single array object (or just after it), and will otherwise invoke undefined behavior. Adding or subtracting from a pointer moves it by a multiple of the size of its datatype. For example, adding 1 to a pointer to 4-byte integer values will increment the pointer's pointed-to byte-address by 4. This has the effect of incrementing the pointer to point at the next element in a contiguous array of integers—which is often the intended result. Pointer arithmetic cannot be performed on codice_86 pointers because the void type has no size, and thus the pointed address can not be added to, although gcc and other compilers will perform byte arithmetic on codice_77 as a non-standard extension, treating it as if it were codice_88.  Pointer arithmetic provides the programmer with a single way of dealing with different types: adding and subtracting the number of elements required instead of the actual offset in bytes. (Pointer arithmetic with codice_88 pointers uses byte offsets, because codice_59 is 1 by definition.) In particular, the C definition explicitly declares that the syntax codice_91, which is the codice_92-th element of the array codice_7, is equivalent to codice_94, which is the content of the element pointed by codice_95. This implies that codice_96 is equivalent to codice_91, and one can write, e.g., codice_98 or codice_99 equally well to access the fourth element of an array codice_7.  While powerful, pointer arithmetic can be a source of computer bugs. It tends to confuse novice programmers, forcing them into different contexts: an expression can be an ordinary arithmetic one or a pointer arithmetic one, and sometimes it is easy to mistake one for the other. In response to this, many modern high-level computer languages (for example Java) do not permit direct access to memory using addresses. Also, the safe C dialect Cyclone addresses many of the issues with pointers. See C programming language for more discussion.  The codice_86 pointer, or codice_77, is supported in ANSI C and C++ as a generic pointer type. A pointer to codice_86 can store the address of any object (not function), and, in C, is implicitly converted to any other object pointer type on assignment, but it must be explicitly cast if dereferenced. K&R C used codice_104 for the “type-agnostic pointer” purpose (before ANSI C). int x = 4; void* p1 = &x; int* p2 = p1; // void* implicitly converted to int*: valid C, but not C++ int a = *p2; int b = *(int*)p1; // when dereferencing inline, there is no implicit conversion C++ does not allow the implicit conversion of codice_77 to other pointer types, even in assignments. This was a design decision to avoid careless and even unintended casts, though most compilers only output warnings, not errors, when encountering other casts. int x = 4; void* p1 = &x; int* p2 = p1; // this fails in C++: there is no implicit conversion from void* int* p3 = (int*)p1; // C-style cast int* p4 = static_cast<int*>(p1); // C++ cast In C++, there is no codice_106 (reference to void) to complement codice_77 (pointer to void), because references behave like aliases to the variables they point to, and there can never be a variable whose type is codice_86.

C#.

In the C# programming language, pointers are supported only under certain conditions: any block of code including pointers must be marked with the codice_109 keyword. Such blocks usually require higher security permissions to be allowed to run. The syntax is essentially the same as in C++, and the address pointed can be either managed or unmanaged memory. However, pointers to managed memory (any pointer to a managed object) must be declared using the codice_110 keyword, which prevents the garbage collector from moving the pointed object as part of memory management while the pointer is

COBOL.

The COBOL programming language supports pointers to variables. Primitive or group (record) data objects declared within the codice_120 of a program are inherently pointer-based, where the only memory allocated within the program is space for the address of the data item (typically a single memory word). In program source code, these data items are used just like any other codice_121

PL/I.

The PL/I language provides full support for pointers to all data types (including pointers to structures), recursion, multitasking, string handling, and extensive built-in functions. PL/I was quite a leap forward compared to the programming languages of its time. PL/I pointers are untyped, and therefore no casting is required for pointer dereferencing or assignment. The declaration syntax for a pointer is codice_133, which declares a pointer named "xxx". Pointers are used with codice_134 variables. A based variable can be

D.

The D programming language is a derivative of

Eiffel.

The Eiffel object-oriented language employs value and reference semantics without pointer arithmetic. Nevertheless,

Fortran.

Fortran-90 introduced a strongly typed pointer capability. Fortran pointers contain more than just a simple memory address. They also encapsulate the lower and upper bounds of array dimensions, strides (for example, to support arbitrary array sections), and other metadata. An "association operator", codice_142 is used to associate a codice_128 to a variable which has a codice_144

Go.

Go has pointers. Its declaration syntax is equivalent to that of C, but written the other way around, ending with the type. Unlike C, Go has garbage collection, and disallows pointer arithmetic. Reference types, like in C++, do not exist. Some built-in

Java.

Unlike C, C++, or Pascal, there is no explicit representation of pointers in Java. Instead, more complex data structures like objects and arrays are implemented using references. The language does

Modula-2.

Pointers are implemented very much as in Pascal, as are codice_148 parameters in procedure calls. Modula-2 is

Oberon.

Much as with Modula-2, pointers are available. There are still fewer ways to evade the type system and

Pascal.

Unlike many languages that feature pointers, standard ISO Pascal only allows pointers to reference dynamically created variables that are anonymous and does not allow them to reference standard static or local variables. It does not have pointer arithmetic. Pointers also must have an associated type and a pointer to one type is not compatible with a pointer to another type (e.g. a pointer to a char is not compatible with a pointer to an integer). This helps eliminate the type security issues inherent with other pointer implementations, particularly those used for PL/I or C. It also removes some risks caused by dangling

Perl.

The Perl programming language supports pointers, although rarely used, in the form of the pack and unpack functions. These are intended only

In computer science, a pointer is a programming language object that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer "references" a location in memory, and obtaining the value stored at that location is known as "dereferencing" the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture.

Ukazatel () je v informatice označení pro datový typ, který slouží k uložení adresy v paměti počítače. Ukazatel slouží pro zpřístupnění dat, která jsou na příslušné adrese v operační paměti uložena.


History.

Formation.

During 1970, "Aérospatiale" was created under the name "SNIAS" as a result of the merger of several French state-owned companies - Sud Aviation, Nord Aviation and Société d'étude et de réalisation d'engins balistiques (SEREB). The newly formed entity was the largest aerospace company in France. From the onset, the French government owned a controlling stake in Aérospatiale; at one stage, a 97 per cent ownership of the company was held by the government.  In 1971, Aérospatiale was directed by the French industrialist Henri Ziegler; that same year, the firm's North American marketing and sales arm, which had previously operated under the trading name of the "French Aerospace Corporation", was officially rebranded as the "European Aerospace Corporation", which was stated to better reflect Aérospatiale's increasing focus on collaborative efforts with its European partners.

Major activities.

Many of Aérospatiale's initial programmes were hangovers from its predecessors, particularly those of Sud Aviation. Perhaps the most iconic and high-profile of the company's programmes was Concorde, a joint French-British attempt to develop and market a supersonic commercial airliner. Initial work on the project had commenced at Sud Aviation and the Bristol Aeroplane Company, its British counterpart. The engines for Concorde were also developed as an Anglo-French joint effort between French engine firm SNECMA and Bristol Siddeley. However, the programme was highly politicised and encountered considerable cost overruns and delays. Ultimately, negatively affected equally by bad political decision and an oil crisis in the 1970s, only two airlines purchased Concorde.  Aérospatiale's senior management were keen not to repeat the mistakes of the programme to produce Concorde. Their next major effort was would be an international collaborative effort between British Aerospace and West German's aircraft company Messerschmitt-Bolkow-Blohm (MBB). The consortium, called Airbus Industrie, was established with the purpose of building a twin-engined widebody airliner, known as the A300. While at first, it was difficult to achieve sales and the outlook for the A300 looked negative. However, Aérospatiale continued to manufacture the jetliner even without orders for some aircraft as it could not reasonably cut back production as French law required that laid-off employees were to receive 90 percent of their pay for a year as well as to retain their health benefits throughout. Sales of the A300 picked up and the type became a major commercial success for those involved, eventually driving both the American Lockheed L-1011 and the McDonnell Douglas DC-10 from the market due to its cheaper operating model. On the back of this success, further airliners would be produced under the Airbus brand and the company would become a world leader in the field of large commercial aircraft during the 1990s.  Aérospatiale played a leadership in the development of the European space sector. During the 1960s, Sud Aviation had been involved in a multinational European programme to produce the Europa space launch vehicle, being a three-stage rocket with separate stages manufactured in Britain, France, and Germany respectively. However, all of the flight tests conducted were failures; the programme's misfortune has been attributed to there being no central authority responsible for operations, which came about as a result of the issue of workshare having become highly politized.  When Aérospatiale stepped in during 1973, it was determined not to repeat the mistakes of Europa. The company proposed to build a new heavy launch vehicle, which would later be called the Ariane, to take the place of Europea. While other European nations were invited to participate, it would be French officials that would be primarily responsible and make the most important decisions. This approach was agreed upon with several other nations; during 1979, the first Ariane performed its first flight, being an immediate success. With this, the French went on to gain a strong advantage over the United States, which had centred its efforts on the Space Shuttle. However, the in-flight explosion of one of the shuttles in the "Challenger" disaster during 1986 showed that it was too complex for routine use as a satellite launch platform. Aérospatiale went on to develop more capable versions of the Ariane, which took much of the business of space launches away from the Americans during the 1990s.

Privatisation and mergers.

In 1992, German defense company DaimlerBenz Aerospace AG (DASA) and Aérospatiale combined their respective helicopter divisions together to form the Eurocopter Group; ownership in this new entity was shared between the two parent companies.  During the late 1990s, French Prime Minister Lionel Jospin's Plural Left government initiated a policy towards the privatization of Aérospatiale. In 1999, the majority of Aérospatiale, except for the satellites activities, merged with French conglomerate Matra's defense wing, Matra Haute Technologie, to form Aérospatiale-Matra. During 2001, Aérospatiale-Matra's missile division underwent a further merger with Anglo-French outfit Matra BAe Dynamics and the missile division of Alenia Marconi Systems to form the multinational MBDA entity.  On 10 July 2000, Aérospatiale-Matra merged with Spanish aviation company Construcciones Aeronáuticas SA (CASA) and German defense firm DaimlerChrysler Aerospace AG (DASA) to form the multinational European Aeronautic Defence and Space Company (EADS). EADS would later rebrand itself as Airbus, taking the name of its commercial aircraft division, its primary business.

Aérospatiale (), sometimes styled Aerospatiale, was a French state-owned aerospace manufacturer that built both civilian and military aircraft, rockets and satellites. It was originally known as Société nationale industrielle aérospatiale (SNIAS). Its head office was in the 16th arrondissement of Paris. The name was changed to Aérospatiale during 1970.

Aérospatiale (původně plným názvem, ~„Národní společnost aerokosmického průmyslu“ či „Národní aerokosmická průmyslová společnost“, zkratkou SNIAS) byl francouzský letecký výrobce, jenž se soustředil na výrobu civilních a vojenských letadel a nosných raket.


Development.

Origins.

During the mid-1980s, ATR sought to introduce a larger airliner with capacity. This new regional airliner, designated as the ATR 72, was directly developed from the earlier ATR 42 and continued to share many commonalities with it; the principal difference between the two airliners was an increase in the maximum seating capacity from 48 to 78 passengers. This was principally achieved by stretching the fuselage by, along with an increase of the wingspan, the use of more powerful engines, and increased fuel capacity by about 10%.  On 15 January 1986, the launch of the stretched ATR 72 programme was announced. On 27 October 1988, the first prototype performed its maiden flight; one year later, on September 25, 1989, the ATR 72 received airworthiness certification from the French Directorate General for Civil Aviation. During the following month, on 27 October 1989, Finnish airline Finnair became the first airline to introduce the aircraft into service. Since the ATR 72 is assembled on the same production line as the smaller ATR 42, along with sharing the majority of subsystems, components, and manufacturing techniques, the two types support each other to remain in production. This factor may have been crucial as, by 2015, the ATR 42 was the only 50-seat regional aircraft that was still being manufactured.  During 2000, the combined global ATR fleet reached its 10,000,000th flight, during which a distance around 4 billion km (2.5 billion statute miles) had been flown and around 450 million passengers had flown on board ATR-built aircraft. The 2007 production set a new record for the programme's sales; a total of 113 new ATR aircraft had been ordered during a single year. By the end of 2014, ATR had received 1,000 orders for the type and delivered a total of 754, leaving a backlog of 246 aircraft.  Within the ATR company, various organisational changes were implemented. On 10 July 1998, ATR launched its new Asset Management Department. In June 2001, EADS and Alenia Aeronautica, ATR's parent companies, decided to reinforce their partnership, regrouping all industrial activities related to regional airliners into the ATR consortium. On 3 October 2003, ATR became one of the first aircraft manufacturers to be certified under ISO 9001-2000 and EN/AS/JISQ 9100, the worldwide quality standard for the aeronautics industry. During July 2004, ATR and Brazilian aircraft manufacturer Embraer announced a co-operation agreement on the AEROChain Portal for the purpose of delivering improved customer service. During April 2009, ATR announced the launch of its 'Door-2-Door' service as a new option in its comprehensive customer services range.

Further development.

Since 2008, ATR has been a participant in the European Clean Sky Joint Technology Initiative. On 8 July 2015, an ATR 72-600 'green' technology demonstrator performed its first flight; the demonstrator was used for testing new composite materials for insulation, air conditioning systems, electrical distribution systems, and energy dispersal modifications to evaluate their effect on the aircraft's overall efficiency as a contribution to the Clean Sky initiative. ATR's senior vice-president for engineering Alessandro Amendola indicated that the elimination of all uses of bleed air was a key aim in the designing of an all-electric architecture as well as improving engine efficiency; the minimising of peak electrical loads was also a stated priority. During March 2016, a second round of flight trials dedicated the testing of all-electric systems architecture using the demonstrator was completed; analysis is set to continue. The current production version is the "ATR 72-600" series. On 2 October 2007, ATR CEO Stéphane Mayer announced the launch of the -600 series aircraft; the ATR 42-600 and ATR 72-600 featured various improvements to increase efficiency, dispatch reliability, lower fuel burn and operating costs. While broadly similar to the earlier -500 model; differences include the adoption of improved PW127M engines, a new glass cockpit, and a variety of other minor improvements.  As a consequence of strong demand for the -600 series, ATR decided to invest in the establishment of a second, more modern final assembly line and acquisition of more hangar space at its Toulouse site, along with a new large completion and delivery area; overall, the manufacturing operation expanded to four times the footprint that it had in 2005. Speaking in October 2015, ATR CEO Patrick de Castelbajac stated that the firm was set to produce in excess of 90 aircraft that year, and that the new manufacturing facilities could support a production rate of up to 120 per year. At the time, the company had a backlog of orders for 300 aircraft, sufficient for three years of production. During 2017, a new in-house financing and leasing division was established by ATR in order to offer customers a greater degree of support and expand the company's range of services.  Considerable emphasis has been placed upon the continuous development of ATR's aircraft models. Speaking at the Farnborough Airshow in July 2016, the CEO of ATR Patrick de Castelbajac stated that the company was currently examining the possibility of replacing the current Pratt & Whitney Canada PW127 engine with either a new offer from P&WC, or a GE38 derivative from GE Aviation. Although expressing satisfaction with the PW127 engine and its supplier, Castelbajac noted the design's age and the need to remain competitive with the latest regional jets. To be a worthwhile exercise, any re-engine exercise would require a 15 per cent improvement in fuel-burn and 20-25 per cent reduction of direct maintenance costs. Additionally, Castelbajac sees the potential re-engine as a "bridge" to the eventual development of a larger 100-seat aircraft.  During the mid-2010s, reports emerged that the development of a further stretched 90-seat ATR model was under consideration as well; allegedly, shareholder Airbus was relatively unenthusiastic on proceeding with such a development, while Airbus CEO Fabrice Brégier favoured a focus on resolving manufacturing issues. However, in January 2018, ATR's parent company Leonardo announced that the 100-seat program has been formally brought to a close.

Design.

The ATR 72 is a turboprop-powered regional airliner, capable of accommodating a maximum of 78 passengers. It is powered by a pair of Pratt & Whitney Canada PW100 turboprop engines, which drive an arrangement of four or six-bladed propellers supplied by Hamilton Standard. Earlier models of the ATR 72 are equipped with the older PW124B engine, rated at 2,400 shp, whilst later-built aircraft are powered by the newer PW127 engine, rated at a maximum of 2,750 shp to achieve improved "hot and high" takeoff performance. It can land and takeoff in high airports with short runways like the Andorra Airport. It employs carbonfibres for 30% of the wing by weight, for a 20% weight reduction.  In a standard configuration, the aircraft does not have an auxiliary power unit; when present it is installed within the C4 cargo section. Most operators of the ATR 72 equip their aircraft with a propeller brake (referred to as "Hotel Mode") that stops the propeller on the No. 2 (right) engine, allowing the turbine to continue running and provide both airflow and electrical power to the aircraft while on the ground.  In the majority of configurations, passengers board the ATR 72 using the rear door, a relatively unusual configuration for a passenger aircraft, while the front door is typically used for the loading and unloading of cargo; early customer Finnair intentionally ordered its ATR 72s with a front passenger door so that it could utilize the jet bridges at Helsinki Airport, while operator Air New Zealand's standard rear door aircraft can use jet bridges at airports with this equipment. While passengers are boarding or disembarking the aircraft, a tail stand is set into place as standard procedure to guard against the aircraft nose lifting off the ground.

Operational history.

2011 was a record-breaking year for sales at ATR. According to ATR's CEO Filippo Bagnato, sales had continued to grow during the Great Recession despite the downturn experienced by most aviation companies as "fuel consumption that can be half that of the alternatives and [with] lower maintenance costs". Bagnato noted the strength of Africa as a market for the type, as well at the firm's aircraft being capable of serving destinations that would otherwise be inaccessible with other aircraft due to the austere conditions of many airstrips and runways in the region, as well as the ability to operate autonomously without any reliance upon ground support equipment.  For 2013, ATR claimed a 48 percent global market share for regional aircraft deliveries between 50 and 90 seats (comprising both turboprops and jets), making it the dominant manufacturer in this market segment. That same year, during which firm orders for 10 ATR 42-600s and 79 ATR 72-600s were recorded, leasing companies were responsible for 70 per cent of these; according to ATR's CEO Filippo Bagnato: "Years ago, we were not even considered by the lessors; now they see ATRs as a good investment". Several major leasing companies operate their own ATR fleets, such as Dubai Aerospace Enterprise (DAE), who placed an order for 20 ATR 72s along with options for another 20 in February 2014, and Nordic Aviation Capital (NAC), who ordered a fleet of 30 ATR 72s during June 2013, along with options for up to 55 further airliners. Placing their first order during 2011, by December 2012, Singaporean leasor Avation had a combined total of 20 ATR 72s on order; by February 2016, the number on order for had risen to 35 aircraft.  During May 1997, ATR achieved their first breakthrough sale in China, placed by operator China Xinjiang Airlines and the Civil Aviation Administration of China (CAAC). By 2013, while the Asia Pacific region had comprised the majority of ATR's sales when geographically ranked; however, orders from Chinese airlines remained elusive; Bagnato ascribed this anomaly to local market conditions dictating the typical use of larger aircraft, as well as a Chinese government policy of imposing high tariffs on the import of foreign-built fixed-wing aircraft. During late 2014, ATR set up a new office in Beijing and hired several former Airbus sales personnel with the aim of launching the type in the Chinese market. ATR believed that many of the already-flown routes did not suit larger 150-seat aircraft; however, of the roughly 2,600 commercial aircraft flying in China at that time, only 68 had a capacity of less than 90 seats and of these, fewer than 20 were powered by turboprop engines.  In response to airlines often wanting to replace their early production ATR models with the latest generation ATR series, as well as to answer demand from cargo operators for the type, ATR has operated two separate dedicated freighter conversion programmes, known as the Bulk Freighter (tube version) and the ULD Freighter. Both conversions involve complete stripping of furnishings along with the addition of floor strengthening, new window plugs and 9g restraining nets, six additional longitudinal tracks for added flexibility, and an E-Class cabin; the ULD model can accommodate standard ULD-packaged cargo, such as LD3 containers or pallets, which were loaded via a large cargo door located on the port forward side. Undertaken by a range of companies, such as Alenia subsidiary Aeronavali, Texas-based M7 Aerospace; French firms Indraéro Siren and Aeroconseil, Canadian Infinion Certification Engineering, and Spanish company Arrodisa, by October 2012, in excess of one-fifth of all first-generation ATR 42 and ATR 72 aircraft had already been converted to freighters.

Iran Air.

During February 2016, ATR signed a deal with flag carrier Iran Air for a batch of 20 ATR 72-600s, along with options for 20 more aircraft and post-purchase services, such as engine maintenance. Made possible by a negotiated relaxation of international sanctions against Iran, during June 2017, a €1 billion Iranian contract was finalised for the 20 airliners; the delivery of the first four aircraft occurred within weeks of the deal being completed. US sanctions against Iran were reimposed in August 2018, by which time 13 of the order of 20 aircraft had been delivered. In April 2019 the US Office of Foreign Assets Control (OFAC) issued a two-year licence to ATR to allow it to supply spare parts and other essentials to keep the fleet of 13 ATR 72-600s in operation. However, the remaining 7 ATR 72-600s from the 2016 order remain sanctioned and in storage.

Turkish Navy.

While primarily used as a civil aircraft, some ATR 72s have been adapted to perform in various military functions, such as utility aircraft and maritime patrol aircraft (MPA). The Turkish Navy, which initially decided to purchase ten ATR 72-500 MPA, later expanded its order to eight aircraft: Two ATR 72-600 TMUA (utility) versions, and six ATR 72-600 TMPA (ASW/ASuW) versions. The armed ATR 72 TMPA variant was developed in cooperation with Turkish Aerospace Industries (TAI), and incorporated additional sensors and mission systems to perform its intended combat role. During 2013, the two ATR 72-600 TMUA aircraft were delivered to the Turkish Navy.

Italian Air Force.

The Italian Air Force also selected the ATR 72-500 MP, designated as the "P-72A", to serve as a multirole maritime patrol, electronic surveillance and C4 platform. The original Italian requirement for a Breguet Atlantic replacement had also called for ASW and anti-surface warfare (ASuW) capabilities, however, during 2014, the contract was renegotiated to a configuration that excluded these capabilities. An anticipated "P-72B" variant for ASW and ASuW operations may later be pursued; accordingly, provisions were made to allow for the four P-72As on order to be adapted to the P-72B configuration. In December 2016, the first pair of P-72A aircraft were delivered to the Italian Air Force.  A single ATR 72 MP was ordered by Italy's paramilitary Guardia di Finanza (GdF) in July 2019, followed by an order for a further three ATR 72s in October 2019. The aircraft will supplement the GdF's existing force of four ATR-42s in the border surveillance, maritime patrol and search and rescue roles.

FedEx Express.

On 8 November 2017, FedEx Express launched the -600 cargo variant with 30 firm orders plus 20 options, in a freighter configuration from the factory.  As of September 2018, 187 early variants had been produced with 172 operated by 55 carriers, 365 -500s were delivered with more than 350 in service at 75 operators, 444 -600s were produced and are operated by 74 carriers with a backlog of orders. By then, with more than 60 -500s and 40 -600s in storage, new aircraft leases fell to $130,000 per month from $170,000. The -600 list price of $26.8M is typically discounted by 25% for a $M value, a 2012 aircraft is valued $13.3M and leased $115,000, falling to $10.2M and $100,000 in 2021, a D check costs $0.5M and the engine overhaul costs $0.3-1.0M.

Variants.

ATR 72-100.

Two sub-types were marketed as the 100 series (-100).

ATR 72-200.

Two sub-types were marketed as the 200 series (-200). The -200 was the original production version, powered by Pratt & Whitney Canada PW124B engines rated at.

ATR 72-210.

Two sub-types were marketed as the 210 series (-210): the -211 (and with an enlarged cargo door, called the -212) is a -200 with PW127 engines producing each for improved performance in hot and high-altitude conditions. The sub-types differ in the type of doors and emergency exits

ATR 72-212A.

Certified in January 1997 and fitted with either PW127F or PW127M engines, the -212A is an upgraded version of the -210 using six-bladed propellers on otherwise identical PW127F engines. Other improvements include higher maximum weights and superior performance, as well as greater automation of power management to ease pilot workload.

Major operators.

Civilian operations.

As of July 2019, 775 ATR 72s were in airline service, with a further 171 on order. Primary ATR 72 airline operators (with 15 aircraft or more) were:

Accidents and incidents.

The ATR 72 has been involved in 46 aviation accidents and incidents including 29 hull losses. Those resulted in 398 fatalities.

The ATR 72 is a twin-engine turboprop, short-haul regional airliner developed and produced in France and Italy by aircraft manufacturer ATR (Aerei da Trasporto Regionale or Avions de transport régional), a joint venture formed by French aerospace company Aérospatiale (now Airbus) and Italian aviation conglomerate Aeritalia (now Leonardo S.p.A.). The number "72" in its name is derived from the aircraft's standard seating configuration in a passenger-carrying configuration, which could seat 72–78 passengers in a single-class arrangement.

ATR 72 je dvoumotorový turbovrtulový úzkotrupý dopravní letoun určený pro kratší regionální tratě. Je výrobkem italsko-francouzské společnosti Aerei di Trasporto Regionale (Avions de Transport Régional, ATR) a vyrábí se v Toulouse, kde firma úzce spolupracuje s výrobcem letadel Airbus.


Display units.

Primary flight display (PFD).

On the flight deck, the display units are the most obvious parts of an EFIS system, and are the features that lead to the term "glass cockpit". The display unit that replaces the ADI is called the primary flight display (PFD). If a separate display replaces the HSI, it is called the navigation display. The PFD displays all information critical to flight, including calibrated airspeed, altitude, heading, attitude, vertical speed and yaw. The PFD is designed to improve a pilot's situational awareness by integrating this information into a single display instead of six different analog instruments, reducing the amount of time necessary to monitor the instruments. PFDs also increase situational awareness by alerting the aircrew to unusual or potentially hazardous conditions — for example, low airspeed, high rate of descent — by changing the color or shape of the display or by providing audio alerts.  The names Electronic Attitude Director Indicator and Electronic Horizontal Situation Indicator are used by some manufacturers. However, a simulated ADI is only the centerpiece of the PFD. Additional information is both superimposed on and arranged around this graphic.  Multi-function displays can render a separate navigation display unnecessary. Another option is to use one large screen to show both the PFD and navigation display.  The PFD and navigation display (and multi-function display, where fitted) are often physically identical. The information displayed is determined by the system interfaces where the display units are fitted. Thus, spares holding is simplified: the one display unit can be fitted in any position.  LCD units generate less heat than CRTs; an advantage in a congested instrument panel. They are also lighter, and occupy a lower volume.

Multi-function display (MFD).

The MFD (multi-function display) displays navigational and weather information from multiple systems. MFDs are most frequently designed as "chart-centric", where the aircrew can overlay different information over a map or chart. Examples of MFD overlay information include the aircraft's current route plan, weather information from either on-board radar or lightning detection sensors or ground-based sensors, e.g., NEXRAD, restricted airspace and aircraft traffic. The MFD can also be used to view other non-overlay type of data (e.g., current route plan) and calculated overlay-type data, e.g., the glide radius of the aircraft, given current location over terrain, winds, and aircraft speed and altitude.  MFDs can also display information about aircraft systems, such as fuel and electrical systems (see EICAS, below). As with the PFD, the MFD can change the color or shape of the data to alert the aircrew to hazardous situations.

Engine indications and crew alerting system (EICAS) / electronic centralized aircraft monitoring (ECAM).

EICAS (Engine Indications and Crew Alerting System) displays information about the aircraft's systems, including its fuel, electrical and propulsion systems (engines). EICAS displays are often designed to mimic traditional round gauges while also supplying digital readouts of the parameters.  EICAS improves situational awareness by allowing the aircrew to view complex information in a graphical format and also by alerting the crew to unusual or hazardous situations. For example, if an engine begins to lose oil pressure, the EICAS might sound an alert, switch the display to the page with the oil system information and outline the low oil pressure data with a red box. Unlike traditional round gauges, many levels of warnings and alarms can be set. Proper care must be taken when designing EICAS to ensure that the aircrew are always provided with the most important information and not overloaded with warnings or alarms.  ECAM is a similar system used by Airbus, which in addition to providing EICAS functions also recommend remedial action.

Control panels.

EFIS provides pilots with controls that select display range and mode (for example, map or compass rose) and enter data (such as selected heading).  Where other equipment uses pilot inputs, data buses broadcast the pilot's selections so that the pilot need only enter the selection once. For example, the pilot selects the desired level-off altitude on a control unit. The EFIS repeats this selected altitude on the PFD, and by comparing it with the actual altitude (from the air data computer) generates an altitude error display. This same altitude selection is used by the automatic flight control system to level off, and by the altitude alerting system to provide appropriate warnings.

Data processors.

The EFIS visual display is produced by the symbol generator. This receives data inputs from the pilot, signals from sensors, and EFIS format selections made by the pilot. The symbol generator can go by other names, such as display processing computer, display electronics unit, etc.  The symbol generator does more than generate symbols. It has (at the least) monitoring facilities, a graphics generator and a display driver. Inputs from sensors and controls arrive via data buses, and are checked for validity. The required computations are performed, and the graphics generator and display driver produce the inputs to the display units.

Capabilities.

Like personal computers, flight instrument systems need power-on-self-test facilities and continuous self-monitoring. Flight instrument systems, however, need additional monitoring capabilities:

Former practice.

Traditional (electromechanical) displays are equipped with synchro mechanisms that transmit the pitch, roll, and heading shown on the captain and first officer's instruments to an instrument comparator. The comparator warns of excessive differences between the Captain and First Officer displays. Even a fault as far "downstream" as a jam in, say, the roll mechanism of an ADI triggers a comparator warning. The instrument comparator thus provides both comparator monitoring and display monitoring.

Comparator monitoring.

With EFIS, the comparator function is simple: Is roll data (bank angle) from sensor 1 the same as roll data from sensor 2? If not, display a warning caption (such as CHECK ROLL) on both PFDs. Comparison monitors give warnings for airspeed, pitch, roll, and altitude indications. More advanced EFIS systems have more comparator monitors.

Display monitoring.

In this technique, each symbol generator contains two display monitoring channels. One channel, the internal, samples the output from its own symbol generator to the display unit and computes, for example, what roll attitude should produce that indication. This computed roll attitude is then compared with the roll attitude input to the symbol generator from the INS or AHRS. Any difference has probably been introduced by faulty processing, and triggers a warning on the relevant display.  The external monitoring channel carries out the same check on the symbol generator on the other side of the flight deck: the Captain's symbol generator checks the First Officer's, the First Officer's checks the Captain's. Whichever symbol generator detects a fault, puts up a warning on its own display.  The external monitoring channel also checks sensor inputs (to the symbol generator) for reasonableness. A spurious input, such as a radio height greater than the radio altimeter's maximum, results in a warning.

Human factors.

Clutter.

At various stages of a flight, a pilot needs different combinations of data. Ideally, the avionics only show the data in use—but an electromechanical instrument must be in view all the time. To improve display clarity, ADIs and HSIs use intricate mechanisms to remove superfluous indications temporarily—e.g., removing the glide slope scale when the pilot doesn't need it.  Under normal conditions, an EFIS might not display some indications, e.g., engine vibration. Only when some parameter exceeds its limits does the system display the reading. In similar fashion, EFIS is programmed to show the glideslope scale and pointer only during an ILS approach.  In the case of an input failure, an electromechanical instrument adds yet another indicator—typically, a bar drops across the erroneous data. EFIS, on the other hand, removes invalid data from the display and substitutes an appropriate warning.  A de-clutter mode activates automatically when circumstances require the pilot's attention for a specific item. For example, if the aircraft pitches up or down beyond a specified limit—usually 30 to 60 degrees—the attitude indicator de-clutters other items from sight until the pilot brings the pitch to an acceptable level. This helps the pilot focus on the most important tasks.

Color.

Traditional instruments have long used color, but lack the ability to change a color to indicate some change in condition. The electronic display technology of EFIS has no such restriction and uses color widely. For example, as an aircraft approaches the glide slope, a blue caption can indicate glide slope is armed, and capture might change the color to green. Typical EFIS systems color code the navigation needles to reflect the type of navigation. Green needles indicate ground based navigation, such as VORs, Localizers and ILS systems. Magenta needles indicate GPS navigation.

Advantages.

EFIS provides versatility by avoiding some physical limitations of traditional instruments. A pilot can switch the same display that shows a course deviation indicator to show the planned track provided by an area navigation or flight management system. Pilots can choose to superimpose the weather radar picture on the displayed route.  The flexibility afforded by software modifications minimises the costs of responding to new aircraft regulations and equipment. Software updates can update an EFIS system to extend its capabilities. Updates introduced in the 1990s included the ground proximity warning system and traffic collision avoidance system.  A degree of redundancy is available even with the simple two-screen EFIS installation. Should the PFD fail, transfer switching repositions its vital information to the screen normally occupied by the navigation display.

Advances in EFIS.

In the late 1980s, EFIS became standard equipment on most Boeing and Airbus airliners, and many business aircraft adopted EFIS in the 1990s.  Recent advances in computing power and reductions in the cost of liquid-crystal displays and navigational sensors (such as GPS and attitude and heading reference system) have brought EFIS to general aviation aircraft. Notable examples are the Garmin G1000 and Chelton Flight Systems EFIS-SV.  Several EFIS manufacturers have focused on the experimental aircraft market, producing EFIS and EICAS systems for as little as US$1,000-2000. The low cost is possible because of steep drops in the price of sensors and displays, and equipment for experimental aircraft doesn't require expensive Federal Aviation Administration certification. This latter point restricts their use to experimental aircraft and certain other aircraft categories, depending on local regulations. Uncertified EFIS systems are also found in Light-sport aircraft, including factory built, microlight, and ultralight aircraft. These systems can be fitted to certified aircraft in some cases as secondary or backup systems depending on local aviation rules.

An electronic flight instrument system (EFIS) is a flight deck instrument display system that displays flight data electronically rather than electromechanically. An EFIS normally consists of a primary flight display (PFD), multi-function display (MFD), and an engine indicating and crew alerting system (EICAS) display. Early EFIS models used cathode ray tube (CRT) displays, but liquid crystal displays (LCD) are now more common. The complex electromechanical attitude director indicator (ADI) and horizontal situation indicator (HSI) were the first candidates for replacement by EFIS. Now, however, few flight deck instruments cannot be replaced by an electronic display.

EFIS (Electronic Flight Information System, "Elektronický letový informační systém") je informační systém, který na display v pilotní kabině zobrazuje letové informace. EFIS je modernější, efektivnější a srozumitelnější než tradiční přístroje („budíky“). V angličtině je EFIS vyslovován jako [ífis].


Etymology.

The pan flute is named after Pan, the Greek god of nature and shepherds often depicted with such an instrument.  In Greek mythology, Syrinx (Σύριγξ) was a forest Nymph. In her attempt to escape the affection of god Pan (a creature half he-goat and half he-man), she was transformed into a water-reed or calamos (cane-reed). Then, Pan cut several reeds, placed them in parallel one next to the other, and bound them together to make a melodic musical instrument. Ancient Greeks called this instrument Syrinx, in honour of the Muse, and Pandean, or Pan-pipes and Pan-flute, after Pan. The Syrinx, a predominantly pastoral instrument for the Greeks, was adopted by the Etruscans who played it at their festivals and banquets; the Etruscans called it fistula. The Romans adopted the Syrinx from the Greeks and the Etruscans, and they too played it at their banquets, festivals, as well as in religious and funeral processions.

Structure.

The pan flute's tubes are stopped at one end, at which the standing wave is reflected giving a note an octave lower than that produced by an open pipe of equal length. In the traditional South American style, pipes are fine-tuned to correct pitch by placing small pebbles or dry corn kernels into the bottom of the pipes. Contemporary makers of curved Romanian-style panpipes use wax (commonly beeswax) to tune new instruments. Special tools are used to place or remove the wax. Corks and rubber stoppers are also used, and are easier to quickly tune pipes.

Acoustics.

The pan flute is an end-blown flute. Sound is produced by the vibration of an air-stream blowing across an open hole at the end of a resonating tube. The length of the tube determines the fundamental frequency. An overblown harmonic register is near a 12th above the fundamental in cylindrical tubes, but can approach an octave jump (8th) if a decreasing taper is used.  According to the Fundamental Principle for pan flutes, the frequency and the length of the tube are inversely proportional. Every time the pitch goes up one octave, the frequency doubles. Because there are 12 notes in a chromatic scale or a full octave, every half-step in a chromatic scale is multiplied by the 12th root of 2 to get the note next to it. By this, it is possible to calculate the length of any pipe, given that one knows the length of any one pipe. The formula for calculating the length of a pan flute pipe is L = (c / f) / 4 (the "theoretical length" L equals the speed of sound c = 343 m/s, divided by the desired frequency in hertz f, that quantity divided by 4; this simplifies and rearranges to: Length of pipe (in centimeters) × Frequency (in hertz) = 8575). Because of a property of compression within the tube, the length must be a little shorter to correct flat pitch. The extra length is helpful for a maker, who can use a cork or plug at the bottom to adjust the pitch. Some instruments use wax or pellets to tune the fundamental pitch of each tube. A tube that has a diameter 1/10 of its length yields a typical tone colour (see Timbre). An inner diameter range between 1/7 and 1/14 of the length L is acceptable. A narrow tube will sound "reedy", while a wide one will sound "flutey". A more exact method is to multiply the bore diameter by 0.82 and subtract this value from the tube length. This compensates for internal compression slowing frequency and the lips partially covering the voicing. Only tiny adjustments will be needed then to adjust fundamental pitch for air density and temperature.

Playing.

The pan flute is played by blowing horizontally across an open end against the sharp inner edge of the pipes. Each pipe is tuned to a keynote, called the fundamental frequency. By overblowing, that is, increasing the pressure of breath and tension of lips, odd harmonics (notes whose frequencies are odd-number multiples of the fundamental), near a 12th in cylindrical tubes, may also be produced. The Romanian pan flute has the pipes arranged in a curved array, solidly glued together, unlike Andean versions, which are usually tied together. Thus, the player can easily reach all the notes by simply swiveling the head, or by moving the instrument with the hands. These instruments can also play all the sharps and flats, with a special technique of both tilting the pipes and jaw movement, thus reducing the size of the pipe's opening and producing a change in pitch. A very advanced player can play any scale and in any key. There are two styles of vibrato possible, hand vibrato and breath vibrato. In hand vibrato, the pitch is shifted up and down, like a vocal vibrato. The player gently moves one end of the pan flute (usually the high end) somewhat similar to violin vibrato. Breath, or throat vibrato, which is really tremolo, a shift in volume, is the same technique used by players of the flute and other woodwinds by use of the player's diaphragm, or throat muscles.

Variations.

The curved-style pan flute was popularized by the Romanian musician Gheorghe Zamfir, who toured extensively and recorded many albums of pan flute music in the 1970s, and by several other artists who began recording at the same time. Today there are thousands of devoted players across Europe, Asia and the Americas. Both the curved and traditional South American variations are also very popular in Peruvian traditional groups and other Andean music.  In Laos and Thailand, there is a cylindrical version called the wot, used in folk music from the Isaan region of the country. The player alters notes by rotating the instrument with the hands, rather than by head movements.  Some new designs are beginning to appear, as designers and makers take advantage of computer-aided design and 3D additive manufacturing, to move past the limitations of traditional tool and materials. These new pan flutes address some long-standing issues to make it an easier instrument to learn and to play accurately.

See also.

Notable pan flute musicians:

Pan Flute (also known as panpipes or syrinx) is a musical instrument based on the principle of the closed tube, consisting of multiple pipes of gradually increasing length (and occasionally girth). Multiple varieties of pan flutes have been popular as folk instruments. The pipes are typically made from bamboo, giant cane, or local reeds. Other materials include wood, plastic, metal and ivory.

Panova flétna nebo také syrinx je dechový hudební nástroj - aerofon. Skládá se z rákosových, třtinových, bambusových či dřevěných píšťalek sestavených do jedné řady. Zvuky z tohoto nástroje se vyluzují pomocí foukání na okraje otvorů píšťalek. Podle řecké mytologie hrává na flétnu bůh pastýřů a stád Pan.


Origins.

The emergence and development of the destroyer was related to the invention of the self-propelled torpedo in the 1860s. A navy now had the potential to destroy a superior enemy battle fleet using steam launches to fire torpedoes. Cheap, fast boats armed with torpedoes called torpedo boats were built and became a threat to large capital ships near enemy coasts. The first seagoing vessel designed to launch the self-propelled Whitehead torpedo was the 33-ton in 1876. She was armed with two drop collars to launch these weapons, these were replaced in 1879 by a single torpedo tube in the bow. By the 1880s, the type had evolved into small ships of 50–100 tons, fast enough to evade enemy picket boats.  At first, the threat of a torpedo boat attack to a battle fleet was considered to exist only when at anchor; but as faster and longer-range torpedoes were developed, the threat extended to cruising at sea. In response to this new threat, more heavily gunned picket boats called "catchers" were built which were used to escort the battle fleet at sea. They needed significant seaworthiness and endurance to operate with the battle fleet, and as they necessarily became larger, they became officially designated "torpedo boat destroyers", and by the First World War were largely known as "destroyers" in English. The anti-torpedo boat origin of this type of ship is retained in its name in other languages, including French ("contre-torpilleur"), Italian ("cacciatorpediniere"), Portuguese ("contratorpedeiro"), Czech ("torpédoborec"), Greek ("antitorpiliko","αντιτορπιλικό"), Dutch ("torpedobootjager") and, up until the Second World War, Polish ("kontrtorpedowiec", now obsolete).  Once destroyers became more than just catchers guarding an anchorage, it was realized that they were also ideal to take over the role of torpedo boats themselves, so they were fitted with torpedo tubes as well as guns. At that time, and even into World War I, the only function of destroyers was to protect their own battle fleet from enemy torpedo attacks and to make such attacks on the battleships of the enemy. The task of escorting merchant convoys was still in the future.

Early designs.

An important development came with the construction of HMS "Swift" in 1884, later redesignated TB 81. This was a large (137 ton) torpedo boat with four 47 mm quick-firing guns and three torpedo tubes. At, while still not fast enough to engage enemy torpedo boats reliably, the ship at least had the armament to deal with them.  Another forerunner of the torpedo boat destroyer was the Japanese torpedo boat ("Falcon"), built in 1885. Designed to Japanese specifications and ordered from the Isle of Dogs, London Yarrow shipyard in 1885, she was transported in parts to Japan, where she was assembled and launched in 1887. The long vessel was armed with four 1-pounder (37 mm) quick-firing guns and six torpedo tubes, reached, and at 203 tons, was the largest torpedo boat built to date. In her trials in 1889, "Kotaka" demonstrated that she could exceed the role of coastal defense, and was capable of accompanying larger warships on the high seas. The Yarrow shipyards, builder of the parts for "Kotaka", "considered Japan to have effectively invented the destroyer".  The German aviso, launched in 1886, was designed as a ""torpedojäger"" (torpedo hunter), intended to screen the fleet against attacks by torpedo boats. The ship was significantly larger than torpedo boats of the period, displacing some, with an armament of guns and Hotchkiss revolver cannon.

Torpedo gunboat.

The first vessel designed for the explicit purpose of hunting and destroying torpedo boats was the torpedo gunboat. Essentially very small cruisers, torpedo gunboats were equipped with torpedo tubes and an adequate gun armament, intended for hunting down smaller enemy boats. By the end of the 1890s torpedo gunboats were made obsolete by their more successful contemporaries, the torpedo boat destroyers, which were much faster.  The first example of this was, designed by Nathaniel Barnaby in 1885, and commissioned in response to the Russian War scare. The gunboat was armed with torpedoes and designed for hunting and destroying smaller torpedo boats. Exactly long and in beam, she displaced 550 tons. Built of steel, "Rattlesnake" was un-armoured with the exception of a -inch protective deck. She was armed with a single 4-inch/25-pounder breech-loading gun, six 3-pounder QF guns and four torpedo tubes, arranged with two fixed tubes at the bow and a set of torpedo dropping carriages on either side. Four torpedo reloads were carried.  A number of torpedo gunboat classes followed, including the "Grasshopper" class, the, the and the – all built for the Royal Navy during the 1880s and the 1890s.  Fernando Villaamil, second officer of the Ministry of the Navy of Spain, designed his own torpedo gunboat to combat the threat from the torpedo boat. He asked several British shipyards to submit proposals capable of fulfilling these specifications. In 1885 the Spanish Navy chose the design submitted by the shipyard of James and George Thomson of Clydebank. ("Destroyer" in Spanish) was laid down at the end of the year, launched in 1886, and commissioned in 1887.  She displaced 348 tons, and was the first warship equipped with twin triple-expansion engines generating, for a maximum speed of, which made her one of the faster ships in the world in 1888. She was armed with one Spanish-designed Hontoria breech-loading gun, four (6-pounder) Nordenfelt guns, two (3-pdr) Hotchkiss cannons and two Schwartzkopff torpedo tubes. The ship carried three torpedoes per tube. She was manned by a crew of 60.  In terms of gunnery, speed and dimensions, the specialised design to chase torpedo boats and her high seas capabilities, "Destructor" was an important precursor to the torpedo boat destroyer.

Development of the modern destroyer.

The first classes of ships to bear the formal designation "torpedo boat destroyer" (TBD) were the of two ships and of two ships of the Royal Navy.  Early torpedo gunboat designs lacked the range and speed to keep up with the fleet they were supposed to protect. In 1892, the Third Sea Lord, Rear Admiral John "Jacky" Fisher ordered the development of a new type of ships equipped with the then novel water-tube boilers and quick-firing small calibre guns. Six ships to the specifications circulated by the Admiralty were ordered initially, comprising three different designs each produced by a different shipbuilder: and from John I. Thornycroft & Company, and from Yarrows, and and from Laird, Son & Company.  These torpedo boat destroyers all featured a turtleback (i.e. rounded) forecastle that was characteristic of early British TBDs. and were both built by Thornycroft, displaced 260 tons (287.8 tons full load) and were 185 feet in length. They were armed with one 12-pounder gun and three 6-pounder guns, with one fixed 18-in torpedo tube in the bow plus two more torpedo tubes on a revolving mount abaft the two funnels. Later the bow torpedo tube was removed and two more 6-pounder guns added instead. They produced 4,200 hp from a pair of Thornycroft water-tube boilers, giving them a top speed of 27 knots, giving the range and speed to travel effectively with a battle fleet. In common with subsequent early Thornycroft boats, they had sloping sterns and double rudders.  The French navy, an extensive user of torpedo boats, built its first torpedo boat destroyer in 1899, with the 'torpilleur d'escadre'. The United States commissioned its first torpedo boat destroyer,, Destroyer No. 1, in 1902 and by 1906 there were 16 destroyers in service with the US Navy.

Subsequent improvements.

Torpedo boat destroyer designs continued to evolve around the turn of the 20th century in several key ways. The first was the introduction of the steam turbine. The spectacular unauthorized demonstration of the turbine powered "Turbinia" at the 1897 Spithead Navy Review, which, significantly, was of torpedo boat size, prompted the Royal Navy to order a prototype turbine powered destroyer, of 1899. This was the first turbine warship of any kind and achieved a remarkable on sea trials. By 1910 the turbine had been widely adopted by all navies for their faster ships.  The second development was the replacement of the torpedo-boat-style turtleback foredeck by a raised forecastle for the new s built in 1903, which provided better sea-keeping as well as more space below deck.  The first warship to use only fuel oil propulsion was the Royal Navy's torpedo boat destroyer, after experiments in 1904, although the obsolescence of coal as a fuel in British warships was delayed by its availability. Other navies also adopted oil, for instance the USN with the of 1909. In spite of all this variety, destroyers adopted a largely similar pattern. The hull was long and narrow, with a relatively shallow draft. The bow was either raised in a forecastle or covered under a turtleback; underneath this were the crew spaces, extending to the way along the hull. Aft of the crew spaces was as much engine space as the technology of the time would allow: several boilers and engines or turbines. Above deck, one or more quick-firing guns were mounted in the bows, in front of the bridge; several more were mounted amidships and astern. Two tube mountings (later on, multiple mountings) were generally found amidships.  Between 1892 and 1914 destroyers became markedly larger: initially 275 tons with a length of for the Royal Navy's first of torpedo boat destroyers, up to the First World War with long destroyers displacing 1000 tons was not unusual. However, construction remained focused on putting the biggest possible engines into a small hull, resulting in a somewhat flimsy construction. Often hulls were built of high-tensile steel only 1/8 in thick.  By 1910 the steam-driven displacement (that is, not hydroplaning) torpedo boat had become redundant as a separate type. Germany nevertheless continued to build such boats until the end of World War I, although these were effectively small coastal destroyers. In fact Germany never distinguished between the two types, giving them pennant numbers in the same series and never giving names to destroyers. Ultimately the term "torpedo boat" came to be attached to a quite different vessel – the very fast hydroplaning motor driven MTB.

Early use and World War I.

Navies originally built torpedo boat destroyers to protect against torpedo boats, but admirals soon appreciated the flexibility of the fast, multi-purpose vessels that resulted. Vice-Admiral Sir Baldwin Walker laid down destroyer duties for the Royal Navy:  Early destroyers were extremely cramped places to live, being "without a doubt magnificent fighting vessels... but unable to stand bad weather". During the Russo-Japanese War in 1904, the commander of the torpedo boat destroyer IJN "Akatsuki" described "being in command of a destroyer for a long period, especially in wartime... is not very good for the health". Stating that he had originally been strong and healthy, he continued, "life on a destroyer in winter, with bad food, no comforts, would sap the powers of the strongest men in the long run. A "destroyer" is always more uncomfortable than the others, and rain, snow, and "sea-water" combine to make them damp; in fact, in bad weather there is not a dry spot where one can rest for a moment."  The Japanese destroyer-commander finished with, "Yesterday I looked at myself in a mirror for a long time; I was disagreeably surprised to see my face thin, full of wrinkles, and as old as though I were fifty. My clothes (uniform) cover nothing but a skeleton, and my bones are full of rheumatism."  In 1898, the US Navy officially classified, a long all steel vessel displacing 165 tons, as a "torpedo boat." However, her commander, LT. John C. Fremont, described her as "...a compact mass of machinery not meant to keep the sea nor to live in... as five sevenths of the ship are taken up by machinery and fuel, whilst the remaining two sevenths, fore and aft, are the crew's quarters; officers forward and the men placed aft. And even in those spaces are placed anchor engines, steering engines, steam pipes, etc. rendering them unbearably hot in tropical regions."

Early combat.

The torpedo boat destroyer's first major use in combat came during the Japanese surprise attack on the Russian fleet anchored in Port Arthur at the opening of the Russo-Japanese War on 8 February 1904.  Three destroyer divisions attacked the Russian fleet in port, firing a total of 18 torpedoes. However, only two Russian battleships, and, as well as the protected cruiser, were seriously damaged due to the proper deployment of torpedo nets. "Tsesarevich", the Russian flagship, had her nets deployed, with at least four enemy torpedoes "hung up" in them, and other warships were similarly saved from further damage by their nets.  While capital ship engagements were scarce in World War I, destroyer units engaged almost continually in raiding and patrol actions. The first shot of the war at sea was fired on 5 August 1914 by a destroyer of the 2nd Flotilla,, in an engagement with the German auxiliary minelayer.  Destroyers were involved in the skirmishes that prompted the Battle of Heligoland Bight, and filled a range of roles in the Battle of Gallipoli, acting as troop transports and as fire-support vessels, as well as their fleet-screening role. Over 80 British destroyers and 60 German torpedo-boats took part in the Battle of Jutland, which involved pitched small-boat actions between the main fleets, and several foolhardy attacks by unsupported destroyers on capital ships. Jutland also concluded with a messy night action between the German High Seas Fleet and part of the British destroyer screen. The threat evolved by World War I with the development of the submarine, or U-boat. The submarine had the potential to hide from gunfire and close underwater to fire torpedoes. Early-war destroyers had the speed and armament to intercept submarines before they submerged, either by gunfire or by ramming. Destroyers also had a shallow enough draft that torpedoes would find it difficult to hit them. The desire to attack submarines underwater led to rapid destroyer evolution during the war. They were quickly equipped with strengthened bows for ramming, and depth charges and hydrophones for identifying submarine targets. The first submarine casualty to a destroyer was the German, rammed by on 29 October 1914. While "U-19" was only damaged, the next month successfully sank. The first depth-charge sinking was on 4 December 1916, when was sunk by HMS "Llewellyn".  The submarine threat meant that many destroyers spent their time on anti-submarine patrol. Once Germany adopted unrestricted submarine warfare in January 1917, destroyers were called on to escort merchant convoys. US Navy destroyers were among the first American units to be dispatched upon the American entry to the war, and a squadron of Japanese destroyers even joined Allied patrols in the Mediterranean. Patrol duty was far from safe; of the 67 British destroyers lost in the war, collisions accounted for 18, while 12 were wrecked.  At the end of the war, the state-of-the-art was represented by the British W class.

1918–1945.

The trend during World War I had been towards larger destroyers with heavier armaments. A number of opportunities to fire at capital ships had been missed during the War, because destroyers had expended all their torpedoes in an initial salvo. The British V and W classes of the late war had sought to address this by mounting six torpedo tubes in two triple mounts, instead of the four or two on earlier models. The 'V' and 'W's set the standard of destroyer building well into the 1920s.  The two Romanian destroyers and, on the other hand, had the greatest firepower of all destroyers in the world throughout the first half of the 1920s. This was largely due to the fact that, between their commissioning in 1920 and 1926, they retained the armament that they had while serving in the Italian Navy as scout cruisers ("esploratori"). When initially ordered by Romania in 1913, the Romanian specifications envisioned three 120 mm guns, a caliber which would eventually be adopted as the standard for future Italian destroyers. Armed with three 152 mm and four 76 mm guns after being completed as scout cruisers, the two warships were officially re-rated as destroyers by the Romanian Navy. The two Romanian warships were thus the destroyers with the greatest firepower in the world throughout much of the interwar period. As of 1939, when the Second World War started, their artillery, although changed, was still close to cruiser standards, amounting to nine heavy naval guns (five of 120 mm and four of 76 mm). In addition, they retained their two twin 457 mm torpedo tubes as well as two machine guns, plus the capacity to carry up to 50 mines.  The next major innovation came with the Japanese or'special type', designed in 1923 and delivered in 1928. The design was initially noted for its powerful armament of six five-inch (127 mm) guns and three triple torpedo mounts. The second batch of the class gave the guns high-angle turrets for anti-aircraft warfare, and the oxygen-fueled 'Long Lance' Type 93 torpedo. The later of 1931 further improved the torpedo armament by storing its reload torpedoes close at hand in the superstructure, allowing reloading within 15 minutes.  Most other nations replied with similar larger ships. The US adopted twin five-inch (127 mm) guns, and the subsequent and es (the latter of 1934) increased the number of torpedo tubes to 12 and 16 respectively. In the Mediterranean, the Italian Navy's building of very fast light cruisers of the prompted the French to produce exceptional destroyer designs. The French had long been keen on large destroyers, with their of 1922 displacing over 2,000 tons and carrying 130 mm guns; a further three similar classes were produced around 1930. The of 1935 carried five guns and nine torpedo tubes, but could achieve speeds of, which remains the record speed for a steamship and for any destroyer. The Italians' own destroyers were almost as swift, most Italian designs of the 1930s being rated at over, while carrying torpedoes and either four or six 120 mm guns.  Germany started to build destroyers again during the 1930s as part of Hitler's rearmament program. The Germans were also fond of large destroyers, but while the initial Type 1934 displaced over 3,000 tons, their armament was equal to smaller vessels. This changed from the Type 1936 onwards, which mounted heavy guns. German destroyers also used innovative high-pressure steam machinery: while this should have helped their efficiency, it more often resulted in mechanical problems.  Once German and Japanese rearmament became clear, the British and American navies consciously focused on building destroyers that were smaller but more numerous than those used by other nations. The British built a series of destroyers (the to ) which were about 1,400 tons standard displacement, had four guns and eight torpedo tubes; the American of 1938 similar in size, but carried five guns and ten torpedo tubes. Realizing the need for heavier gun armament, the British built the of 1936 (sometimes called "Afridi" after one of two lead ships). These ships displaced 1,850 tons and were armed with eight guns in four twin turrets and four torpedo tubes. These were followed by the J-class and L-class destroyers, with six guns in twin turrets and eight torpedo tubes.  Anti-submarine sensors included sonar (or ASDIC), although training in their use was indifferent. Anti-submarine weapons changed little, and ahead-throwing weapons, a need recognized in World War I, had made no progress.

Later combat.

During the 1920s and 1930s, destroyers were often deployed to areas of diplomatic tension or humanitarian disaster. British and American destroyers were common on the Chinese coast and rivers, even supplying landing parties to protect colonial interests.  By World War II the threat had evolved once again. Submarines were more effective, and aircraft had become important weapons of naval warfare; once again the early-war fleet destroyers were ill-equipped for combating these new targets. They were fitted with new light anti-aircraft guns, radar, and forward-launched ASW weapons, in addition to their existing dual-purpose guns, depth charges, and torpedoes. Increasing size allowed improved internal arrangement of propulsion machinery with compartmentation so ships were less likely to be sunk by a single hit. In most cases torpedo and/or dual-purpose gun armament was reduced to accommodate new anti-air and anti-submarine weapons. By this time the destroyers had become large, multi-purpose vessels, expensive targets in their own right. As a result, casualties on destroyers were among the highest.  The need for large numbers of anti-submarine ships led to the introduction of smaller and cheaper specialized anti-submarine warships called corvettes and frigates by the Royal Navy and destroyer escorts by the USN. A similar programme was belatedly started by the Japanese (see ). These ships had the size and displacement of the original torpedo boat destroyers that the contemporary destroyer had evolved from.

Post-World War II.

Some conventional destroyers were completed in the late 1940s and 1950s which built on wartime experience. These vessels were significantly larger than wartime ships and had fully automatic main guns, unit machinery, radar, sonar, and antisubmarine weapons such as the Squid mortar. Examples include the British, US, and the Soviet s.  Some World War II–vintage ships were modernized for anti-submarine warfare, and to extend their service lives, to avoid having to build (expensive) brand-new ships. Examples include the US FRAM I programme and the British Type 15 frigates converted from fleet destroyers.  The advent of surface-to-air missiles and surface-to-surface missiles, such as the Exocet, in the early 1960s changed naval warfare. Guided missile destroyers (DDG in the US Navy) were developed to carry these weapons and protect the fleet from air, submarine and surface threats. Examples include the Soviet, the British, and the US.  21st century destroyers tend to display features such as large, slab sides without complicated corners and crevices to keep the radar cross-section small, vertical launch systems to carry a large number of missiles at high readiness to fire and helicopter flight decks and hangars.

Future development.

is currently in the process of adding up to 18 ships of the Type 052D destroyer class. Serial construction is underway for at-least 6 of the larger and more powerful Type 055 destroyer, which at the current rate of production, should be complete by late 2019 or early 2020.  In addition, six multi-mission surface combat ships are planned under the name 'Mehrzweckkampfschiff 180' (MKS 180), which will have destroyer-size and corresponding capabilities (length: 163m, displacement: 10,400 tons) , as of 2018, has 67 active "Arleigh Burke" destroyers and 15 planned or under construction. The new ships will be the upgraded "flight III" version. Each "Arleigh Burke" will remain in commission for at least 45 years, with the oldest operating until after 2035 and the newest operating until after 2080. There are no plans for any additional destroyers beyond the third.

Preserved destroyers.

A number of countries have destroyers preserved as museum ships. These include:

In naval terminology, a destroyer is a fast, maneuverable, long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against powerful short range attackers. They were originally developed in the late 19th century by Fernando Villaamil for the Spanish Navy as a defense against torpedo boats, and by the time of the Russo-Japanese War in 1904, these "torpedo boat destroyers" (TBDs) were "large, swift, and powerfully armed torpedo boats designed to destroy other torpedo boats". Although the term "destroyer" had been used interchangeably with "TBD" and "torpedo boat destroyer" by navies since 1892, the term "torpedo boat destroyer" had been generally shortened to simply "destroyer" by nearly all navies by the First World War.

Torpédoborec je rychlá a obratná válečná loď se silnou raketovou, hlavňovou a torpédovou výzbrojí, určená k plnění mnoha různorodých úkolů. Jeho hlavním úkolem je vedení boje s letadly, ponorkami a hladinovými loděmi protivníka na otevřeném moři. Slouží též jako doprovod velkých lodí ve flotile nebo bojové skupině.


History.

The increasing demand and usage of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation.  A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974. Ethernet was developed at Xerox PARC between 1973 and 1974. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.  The development and proliferation of personal computers using the CP/M operating system in the late 1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was to share storage and printers, both of which were expensive at the time. There was much enthusiasm for the concept, and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, "The year of the LAN".  In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. A solution appeared with the advent of Novell NetWare which provided even-handed support for dozens of competing card and cable types, and a much more sophisticated operating system than most of its competitors. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT.  Of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. 3Com produced 3+Share and Microsoft produced MS-Net. These then formed the basis for collaboration between Microsoft and 3Com to create a simple network operating system LAN Manager and its cousin, IBM's LAN Server. None of these enjoyed any lasting success.  In 1983, TCP/IP was first shown capable of supporting actual defense department applications on a Defense Communication Agency LAN test bed located at Reston, Virginia. The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department teleconferencing application. This demonstrated the feasibility of employing TCP/IP LANs to interconnect Worldwide Military Command and Control System (WWMCCS) computers at command centers throughout the United States. However, WWMCCS was superseded by the Global Command and Control System (GCCS) before that could happen.  During the same period, Unix workstations were using TCP/IP networking. Although this market segment is now much reduced, the technologies developed in this area continue to be influential on the Internet and in both Linux and Apple Mac OS X networking—and the TCP/IP protocol has replaced IPX, AppleTalk, NBF, and other protocols used by the early PC LANs.

Cabling.

Early Ethernet (10BASE-5 and 10BASE-2) used coaxial cable. Shielded twisted pair was used in IBM's Token Ring LAN implementation. In 1984, StarLAN showed the potential of simple unshielded twisted pair by using category 3 cable—the same cable used for telephone systems. This led to the development of 10BASE-T (and its twisted-pair successors) and structured cabling which is still the basis of most commercial LANs today.  While optical fiber cable is common for links between network switches, use of fiber to the desktop is rare.

Wireless media.

In a wireless LAN, users have unrestricted movement within the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Most wireless LANs use Wi-Fi as it is built into smartphones, tablet computers and laptops. Guests are often offered Internet access via a hotspot service.

Technical aspects.

Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star.  Simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, or ADSL modem for Internet access. A LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection. Advanced LANs are characterized by their use of redundant links with switches using the spanning tree protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and their ability to segregate traffic with VLANs.  At the higher network layers, protocols such as NetBIOS, IPX/SPX, AppleTalk and others were once common, but the Internet protocol suite (TCP/IP) has prevailed as the standard of choice.  LANs can maintain connections with other LANs via leased lines, leased services, or across the Internet using virtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network (MAN) or a wide area network (WAN).

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits.

Local Area Network (též LAN, lokální síť, místní síť) označuje počítačovou síť, která pokrývá malé geografické území (např. domácnosti, malé firmy). Přenosové rychlosti jsou vysoké, řádově Gb/s. Nejrozšířenějšími technologiemi v dnešních LAN sítích jsou Ethernet a Wi-Fi (nebo také WLAN), v minulosti byly používány např. ARCNET a Token Ring.


Biography.

Born in Oslo, Aamodt is the only alpine skier to win 8 Olympic medals, and has won 5 World Championship gold medals as well as 21 individual World Cup events. Described as an all-round alpine skier, Aamodt participated in all alpine skiing disciplines in the World Cup and World Championships, and is one of only 5 male alpine skiers to have won a World Cup race in all five disciplines.  Aamodt's combined career total of twenty World Championship and Olympic medals is an all-time best. He is the second-youngest male alpine skier to win an Olympic gold medal (age 20 in 1992; Toni Sailer was two months younger in 1956). Until 2014, he was also the oldest alpine skier to win an Olympic gold medal. For almost six years, Aamodt led the all-time Marathon World Cup ranking, with a total of 13,252 points earned from 1989 to 2006 – until 14 March 2012, when Austrian Benjamin Raich overtook him with a fifth place in the downhill at the 2012 World Cup final in Schladming to total 13,281 points, earned from 1998. Another all-time best is his 231 World Cup top-ten results, 9 ahead of Benjamin Raich.  By winning the super-G race at the 2006 Olympics, Aamodt became the first male alpine skier to win four gold medals in the Olympics. (Toni Sailer and Jean-Claude Killy both swept the three alpine events at a single Olympics.)  Aamodt had 19 Olympic and World Championship medals stolen from him. The medals were taken in August 2003 by burglars who broke into a safe in his father's home. The five-time world champion and winner of four Olympic gold medals later revealed they were recovered by an anonymous helper over the internet.  Aamodt announced the conclusion of his career on live television on 6 January 2007, with hundreds of fellow athletes in attendance, at the Norwegian Sports Gala (Idrettsgallaen) where he had been selected as awardee of the year for 2006.  Aamodt now runs a ski race camp in Gaustablikk, Norway, and does public speaking.

Legacy.

In February 2015 Aamodt (and Lasse Kjus) were selected as recipients of the Legends of Honor by the Vail Valley Foundation, and inducted into the International Ski Racing Hall of Fame.

World Cup results.

Season titles.

1 overall, 1 super-G, 1 giant slalom, 1 slalom

Kjetil André Aamodt (born 2 September 1971) is a former World Cup alpine ski racer from Norway, a champion in the Olympics, World Championships, and World Cup. He is the most decorated ski racer from Norway.

Kjetil André Aamodt (2. září 1971 Oslo) je norský lyžař, dlouholetý úspěšný reprezentant v alpském lyžování. Je jediným lyžařem alpských disciplín, který vyhrál osm olympijských medailí; stal se pětkrát mistrem světa.