title: Holography

text: A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest.


title: Holography

text: The Hungarian-British physicist Dennis Gabor (in Hungarian: "Gábor Dénes") was awarded the Nobel Prize in Physics in 1971 "for his invention and development of the holographic method".


title: Holography

text: His work, done in the late 1940s, was built on pioneering work in the field of X-ray microscopy by other scientists including Mieczysław Wolfke in 1920 and William Lawrence Bragg in 1939. This discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company (BTH) in Rugby, England, and the company filed a patent in December 1947 (patent GB685286). The technique as originally invented is still used in electron microscopy, where it is known as electron holography, but optical holography did not really advance until the development of the laser in 1960. The word "holography" comes from the Greek words ("holos"; "whole") and ("graphē"; "writing" or "drawing").


title: Holography

text: A hologram is a recording of an interference pattern which can reproduce a 3D light field using diffraction. The reproduced light field can generate an image which still has the depth, parallax, and other properties of the original scene. A hologram is a photographic recording of a light field, rather than an image formed by a lens. The holographic medium, for example the object produced by a holographic process (which may be referred to as a hologram) is usually unintelligible when viewed under diffuse ambient light. It is an encoding of the light field as an interference pattern of variations in the opacity, density, or surface profile of the photographic medium. When suitably lit, the interference pattern diffracts the light into an accurate reproduction of the original light field, and the objects that were in it exhibit visual depth cues such as parallax and perspective that change realistically with the different angles of viewing. That is, the view of the image from different angles represents the subject viewed from similar angles. In this sense, holograms do not have just the illusion of depth but are truly three-dimensional images.


title: Holography

text: The development of the laser enabled the first practical optical holograms that recorded 3D objects to be made in 1962 by Yuri Denisyuk in the Soviet Union and by Emmett Leith and Juris Upatnieks at the University of Michigan, USA. Early holograms used silver halide photographic emulsions as the recording medium. They were not very efficient as the produced grating absorbed much of the incident light. Various methods of converting the variation in transmission to a variation in refractive index (known as "bleaching") were developed which enabled much more efficient holograms to be produced.


title: Holography

text: Optical holography needs a laser light to record the light field. In its early days, holography required high-power and expensive lasers, but currently, mass-produced low-cost laser diodes, such as those found on DVD recorders and used in other common applications, can be used to make holograms and have made holography much more accessible to low-budget researchers, artists and dedicated hobbyists. A microscopic level of detail throughout the recorded scene can be reproduced. The 3D image can, however, be viewed with non-laser light. In common practice, however, major image quality compromises are made to remove the need for laser illumination to view the hologram, and in some cases, to make it. Holographic portraiture often resorts to a non-holographic intermediate imaging procedure, to avoid the dangerous high-powered pulsed lasers which would be needed to optically "freeze" moving subjects as perfectly as the extremely motion-intolerant holographic recording process requires. Holograms can now also be entirely computer-generated to show objects or scenes that never existed. Most holograms produced are of static objects but systems for displaying changing scenes on a holographic volumetric display are now being developed.


title: Holography

text: Holography is a technique that enables a light field (which is generally the result of a light source scattered off objects) to be recorded and later reconstructed when the original light field is no longer present, due to the absence of the original objects. Holography can be thought of as somewhat similar to sound recording, whereby a sound field created by vibrating matter like musical instruments or vocal cords, is encoded in such a way that it can be reproduced later, without the presence of the original vibrating matter. However, it is even more similar to Ambisonic sound recording in which any listening angle of a sound field can be reproduced in the reproduction.


title: Holography

text: In laser holography, the hologram is recorded using a source of laser light, which is very pure in its color and orderly in its composition. Various setups may be used, and several types of holograms can be made, but all involve the interaction of light coming from different directions and producing a microscopic interference pattern which a plate, film, or other medium photographically records.


title: Holography

text: In one common arrangement, the laser beam is split into two, one known as the object beam and the other as the reference beam. The object beam is expanded by passing it through a lens and used to illuminate the subject. The recording medium is located where this light, after being reflected or scattered by the subject, will strike it. The edges of the medium will ultimately serve as a window through which the subject is seen, so its location is chosen with that in mind. The reference beam is expanded and made to shine directly on the medium, where it interacts with the light coming from the subject to create the desired interference pattern.


title: Holography

text: Like conventional photography, holography requires an appropriate exposure time to correctly affect the recording medium. Unlike conventional photography, during the exposure the light source, the optical elements, the recording medium, and the subject must all remain motionless relative to each other, to within about a quarter of the wavelength of the light, or the interference pattern will be blurred and the hologram spoiled. With living subjects and some unstable materials, that is only possible if a very intense and extremely brief pulse of laser light is used, a hazardous procedure which is rarely done outside of scientific and industrial laboratory settings. Exposures lasting several seconds to several minutes, using a much lower-powered continuously operating laser, are typical.


title: Holography

text: A hologram can be made by shining part of the light beam directly into the recording medium, and the other part onto the object in such a way that some of the scattered light falls onto the recording medium. A more flexible arrangement for recording a hologram requires the laser beam to be aimed through a series of elements that change it in different ways. The first element is a beam splitter that divides the beam into two identical beams, each aimed in different directions:


title: Holography

text: Several different materials can be used as the recording medium. One of the most common is a film very similar to photographic film (silver halide photographic emulsion), but with much smaller light-reactive grains (preferably with diameters less than 20 nm), making it capable of the much higher resolution that holograms require. A layer of this recording medium (e.g., silver halide) is attached to a transparent substrate, which is commonly glass, but may also be plastic.


title: Holography

text: When the two laser beams reach the recording medium, their light waves intersect and interfere with each other. It is this interference pattern that is imprinted on the recording medium. The pattern itself is seemingly random, as it represents the way in which the scene's light "interfered" with the original light source – but not the original light source itself. The interference pattern can be considered an encoded version of the scene, requiring a particular key – the original light source – in order to view its contents.


title: Holography

text: This missing key is provided later by shining a laser, identical to the one used to record the hologram, onto the developed film. When this beam illuminates the hologram, it is diffracted by the hologram's surface pattern. This produces a light field identical to the one originally produced by the scene and scattered onto the hologram.


title: Holography

text: For a better understanding of the process, it is necessary to understand interference and diffraction. Interference occurs when one or more wavefronts are superimposed. Diffraction occurs when a wavefront encounters an object. The process of producing a holographic reconstruction is explained below purely in terms of interference and diffraction. It is somewhat simplified but is accurate enough to give an understanding of how the holographic process works.


title: Holography

text: For those unfamiliar with these concepts, it is worthwhile to read those articles before reading further in this article.


title: Holography

text: A diffraction grating is a structure with a repeating pattern. A simple example is a metal plate with slits cut at regular intervals. A light wave that is incident on a grating is split into several waves; the direction of these diffracted waves is determined by the grating spacing and the wavelength of the light.


title: Holography

text: A simple hologram can be made by superimposing two plane waves from the same light source on a holographic recording medium. The two waves interfere, giving a straight-line fringe pattern whose intensity varies sinusoidally across the medium. The spacing of the fringe pattern is determined by the angle between the two waves, and by the wavelength of the light.


title: Holography

text: The recorded light pattern is a diffraction grating. When it is illuminated by only one of the waves used to create it, it can be shown that one of the diffracted waves emerges at the same angle at which the second wave was originally incident, so that the second wave has been 'reconstructed'. Thus, the recorded light pattern is a holographic recording as defined above.


title: Holography

text: If the recording medium is illuminated with a point source and a normally incident plane wave, the resulting pattern is a sinusoidal zone plate, which acts as a negative Fresnel lens whose focal length is equal to the separation of the point source and the recording plane.


title: Holography

text: When a plane wave-front illuminates a negative lens, it is expanded into a wave that appears to diverge from the focal point of the lens. Thus, when the recorded pattern is illuminated with the original plane wave, some of the light is diffracted into a diverging beam equivalent to the original spherical wave; a holographic recording of the point source has been created.


title: Holography

text: When the plane wave is incident at a non-normal angle at the time of recording, the pattern formed is more complex, but still acts as a negative lens if it is illuminated at the original angle.


title: Holography

text: To record a hologram of a complex object, a laser beam is first split into two beams of light. One beam illuminates the object, which then scatters light onto the recording medium. According to diffraction theory, each point in the object acts as a point source of light so the recording medium can be considered to be illuminated by a set of point sources located at varying distances from the medium.


title: Holography

text: The second (reference) beam illuminates the recording medium directly. Each point source wave interferes with the reference beam, giving rise to its own sinusoidal zone plate in the recording medium. The resulting pattern is the sum of all these 'zone plates', which combine to produce a random (speckle) pattern as in the photograph above.


title: Holography

text: When the hologram is illuminated by the original reference beam, each of the individual zone plates reconstructs the object wave that produced it, and these individual wavefronts are combined to reconstruct the whole of the object beam. The viewer perceives a wavefront that is identical with the wavefront scattered from the object onto the recording medium, so that it appears that the object is still in place even if it has been removed.


title: Holography

text: Early on, artists saw the potential of holography as a medium and gained access to science laboratories to create their work. Holographic art is often the result of collaborations between scientists and artists, although some holographers would regard themselves as both an artist and a scientist.


title: Holography

text: Salvador Dalí claimed to have been the first to employ holography artistically. He was certainly the first and best-known surrealist to do so, but the 1972 New York exhibit of Dalí holograms had been preceded by the holographic art exhibition that was held at the Cranbrook Academy of Art in Michigan in 1968 and by the one at the Finch College gallery in New York in 1970, which attracted national media attention. In Great Britain, Margaret Benyon began using holography as an artistic medium in the late 1960s and had a solo exhibition at the University of Nottingham art gallery in 1969. This was followed in 1970 by a solo show at the Lisson Gallery in London, which was billed as the "first London expo of holograms and stereoscopic paintings".


title: Holography

text: During the 1970s, a number of art studios and schools were established, each with their particular approach to holography. Notably, there was the San Francisco School of Holography established by Lloyd Cross, The Museum of Holography in New York founded by Rosemary (Posy) H. Jackson, the Royal College of Art in London and the Lake Forest College Symposiums organised by Tung Jeong. None of these studios still exist; however, there is the Center for the Holographic Arts in New York and the HOLOcenter in Seoul, which offers artists a place to create and exhibit work.


title: Holography

text: During the 1980s, many artists who worked with holography helped the diffusion of this so-called "new medium" in the art world, such as Harriet Casdin-Silver of the United States, Dieter Jung of Germany, and Moysés Baumstein of Brazil, each one searching for a proper "language" to use with the three-dimensional work, avoiding the simple holographic reproduction of a sculpture or object. For instance, in Brazil, many concrete poets (Augusto de Campos, Décio Pignatari, Julio Plaza and José Wagner Garcia, associated with Moysés Baumstein) found in holography a way to express themselves and to renew Concrete Poetry.


title: Holography

text: A small but active group of artists still integrate holographic elements into their work. Some are associated with novel holographic techniques; for example, artist Matt Brand employed computational mirror design to eliminate image distortion from specular holography.


title: Holography

text: The MIT Museum and Jonathan Ross both have extensive collections of holography and on-line catalogues of art holograms.


title: Holography

text: Holographic data storage is a technique that can store information at high density inside crystals or photopolymers. The ability to store large amounts of information in some kind of medium is of great importance, as many electronic products incorporate storage devices. As current storage techniques such as Blu-ray Disc reach the limit of possible data density (due to the diffraction-limited size of the writing beams), holographic storage has the potential to become the next generation of popular storage media. The advantage of this type of data storage is that the volume of the recording media is used instead of just the surface.


title: Holography

text: Currently available SLMs can produce about 1000 different images a second at 1024×1024-bit resolution which would result in about one-gigabit-per-second writing speed.


title: Holography

text: In 2005, companies such as Optware and Maxell produced a 120 mm disc that uses a holographic layer to store data to a potential 3.9 TB, a format called Holographic Versatile Disc. As of September 2014, no commercial product has been released.


title: Holography

text: Another company, InPhase Technologies, was developing a competing format, but went bankrupt in 2011 and all its assets were sold to Akonia Holographics, LLC.


title: Holography

text: While many holographic data storage models have used "page-based" storage, where each recorded hologram holds a large amount of data, more recent research into using submicrometre-sized "microholograms" has resulted in several potential 3D optical data storage solutions. While this approach to data storage can not attain the high data rates of page-based storage, the tolerances, technological hurdles, and cost of producing a commercial product are significantly lower.


title: Holography

text: In static holography, recording, developing and reconstructing occur sequentially, and a permanent hologram is produced.


title: Holography

text: There also exist holographic materials that do not need the developing process and can record a hologram in a very short time. This allows one to use holography to perform some simple operations in an all-optical way. Examples of applications of such real-time holograms include phase-conjugate mirrors ("time-reversal" of light), optical cache memories, image processing (pattern recognition of time-varying images), and optical computing.


title: Holography

text: The amount of processed information can be very high (terabits/s), since the operation is performed in parallel on a whole image. This compensates for the fact that the recording time, which is in the order of a microsecond, is still very long compared to the processing time of an electronic computer. The optical processing performed by a dynamic hologram is also much less flexible than electronic processing. On one side, one has to perform the operation always on the whole image, and on the other side, the operation a hologram can perform is basically either a multiplication or a phase conjugation. In optics, addition and Fourier transform are already easily performed in linear materials, the latter simply by a lens. This enables some applications, such as a device that compares images in an optical way.


title: Holography

text: The search for novel for dynamic holography is an active area of research. The most common materials are photorefractive crystals, but in semiconductors or semiconductor heterostructures (such as quantum wells), atomic vapors and gases, plasmas and even liquids, it was possible to generate holograms.


title: Holography

text: A particularly promising application is optical phase conjugation. It allows the removal of the wavefront distortions a light beam receives when passing through an aberrating medium, by sending it back through the same aberrating medium with a conjugated phase. This is useful, for example, in free-space optical communications to compensate for atmospheric turbulence (the phenomenon that gives rise to the twinkling of starlight).


title: Holography

text: In 1971, Lloyd Cross opened the San Francisco School of Holography and taught amateurs how to make holograms using only a small (typically 5 mW) helium-neon laser and inexpensive home-made equipment. Holography had been supposed to require a very expensive metal optical table set-up to lock all the involved elements down in place and damp any vibrations that could blur the interference fringes and ruin the hologram. Cross's home-brew alternative was a sandbox made of a cinder block retaining wall on a plywood base, supported on stacks of old tires to isolate it from ground vibrations, and filled with sand that had been washed to remove dust. The laser was securely mounted atop the cinder block wall. The mirrors and simple lenses needed for directing, splitting and expanding the laser beam were affixed to short lengths of PVC pipe, which were stuck into the sand at the desired locations. The subject and the photographic plate holder were similarly supported within the sandbox. The holographer turned off the room light, blocked the laser beam near its source using a small relay-controlled shutter, loaded a plate into the holder in the dark, left the room, waited a few minutes to let everything settle, then made the exposure by remotely operating the laser shutter.


title: Holography

text: Many of these holographers would go on to produce art holograms. In 1983, Fred Unterseher, a co-founder of the San Francisco School of Holography and a well-known holographic artist, published the "Holography Handbook", an easy-to-read guide to making holograms at home. This brought in a new wave of holographers and provided simple methods for using the then-available AGFA silver halide recording materials.


title: Holography

text: In 2000, Frank DeFreitas published the "Shoebox Holography Book" and introduced the use of inexpensive laser pointers to countless hobbyists. For many years, it had been assumed that certain characteristics of semiconductor laser diodes made them virtually useless for creating holograms, but when they were eventually put to the test of practical experiment, it was found that not only was this untrue, but that some actually provided a coherence length much greater than that of traditional helium-neon gas lasers. This was a very important development for amateurs, as the price of red laser diodes had dropped from hundreds of dollars in the early 1980s to about $5 after they entered the mass market as a component of DVD players in the late 1990s. Now, there are thousands of amateur holographers worldwide.


title: Holography

text: By late 2000, holography kits with inexpensive laser pointer diodes entered the mainstream consumer market. These kits enabled students, teachers, and hobbyists to make several kinds of holograms without specialized equipment, and became popular gift items by 2005. The introduction of holography kits with self-developing plates in 2003 made it possible for hobbyists to create holograms without the bother of wet chemical processing.


title: Holography

text: In 2006, a large number of surplus holography-quality green lasers (Coherent C315) became available and put dichromated gelatin (DCG) holography within the reach of the amateur holographer. The holography community was surprised at the amazing sensitivity of DCG to green light. It had been assumed that this sensitivity would be uselessly slight or non-existent. Jeff Blyth responded with the G307 formulation of DCG to increase the speed and sensitivity to these new lasers.


title: Holography

text: Kodak and Agfa, the former major suppliers of holography-quality silver halide plates and films, are no longer in the market. While other manufacturers have helped fill the void, many amateurs are now making their own materials. The favorite formulations are dichromated gelatin, Methylene-Blue-sensitised dichromated gelatin, and diffusion method silver halide preparations. Jeff Blyth has published very accurate methods for making these in a small lab or garage.


title: Holography

text: A small group of amateurs are even constructing their own pulsed lasers to make holograms of living subjects and other unsteady or moving objects.


title: Holography

text: Holographic interferometry (HI) is a technique that enables static and dynamic displacements of objects with optically rough surfaces to be measured to optical interferometric precision (i.e. to fractions of a wavelength of light). It can also be used to detect optical-path-length variations in transparent media, which enables, for example, fluid flow to be visualized and analyzed. It can also be used to generate contours representing the form of the surface or the isodose regions in radiation dosimetry.


title: Holography

text: The hologram keeps the information on the amplitude and phase of the field. Several holograms may keep information about the same distribution of light, emitted to various directions. The numerical analysis of such holograms allows one to emulate large numerical aperture, which, in turn, enables enhancement of the resolution of optical microscopy. The corresponding technique is called interferometric microscopy. Recent achievements of interferometric microscopy allow one to approach the quarter-wavelength limit of resolution.


title: Holography

text: The hologram is made with a modified material that interacts with certain molecules generating a change in the fringe periodicity or refractive index, therefore, the color of the holographic reflection.


title: Holography

text: Holograms are commonly used for security, as they are replicated from a master hologram that requires expensive, specialized and technologically advanced equipment, and are thus difficult to forge. They are used widely in many currencies, such as the Brazilian 20, 50, and 100-reais notes; British 5, 10, and 20-pound notes; South Korean 5000, 10,000, and 50,000-won notes; Japanese 5000 and 10,000 yen notes, Indian 50, 100, 500, and 2000 rupee notes; and all the currently-circulating banknotes of the Canadian dollar, Croatian kuna, Danish krone, and Euro. They can also be found in credit and bank cards as well as passports, ID cards, books, food packaging, DVDs, and sports equipment. Such holograms come in a variety of forms, from adhesive strips that are laminated on packaging for fast-moving consumer goods to holographic tags on electronic products. They often contain textual or pictorial elements to protect identities and separate genuine articles from counterfeits.


title: Holography

text: Holographic scanners are in use in post offices, larger shipping firms, and automated conveyor systems to determine the three-dimensional size of a package. They are often used in tandem with checkweighers to allow automated pre-packing of given volumes, such as a truck or pallet for bulk shipment of goods.


title: Holography

text: Holograms produced in elastomers can be used as stress-strain reporters due to its elasticity and compressibility, the pressure and force applied are correlated to the reflected wavelength, therefore its color. Holography technique can also be effectively used for radiation dosimetry.


title: Holography

text: High-security holograms can be used on license plates for vehicles such as cars and motorcycles. As of April 2019, holographic license plates are required on vehicles in parts of India to aid in identification and security, especially in cases of car theft. Such number plates hold electronic data of vehicles, and have a unique ID number and a sticker to indicate authenticity.


title: Holography

text: Electron holography is the application of holography techniques to electron waves rather than light waves. Electron holography was invented by Dennis Gabor to improve the resolution and avoid the aberrations of the transmission electron microscope. Today it is commonly used to study electric and magnetic fields in thin films, as magnetic and electric fields can shift the phase of the interfering wave passing through the sample. The principle of electron holography can also be applied to interference lithography.


title: Holography

text: Acoustic holography enables sound maps of an object to be generated. Measurements of the acoustic field are made at many points close to the object. These measurements are digitally processed to produce the “images” of the object.


title: Holography

text: Atomic holography has evolved out of the development of the basic elements of atom optics. With the Fresnel diffraction lens and atomic mirrors atomic holography follows a natural step in the development of the physics (and applications) of atomic beams. Recent developments including atomic mirrors and especially ridged mirrors have provided the tools necessary for the creation of atomic holograms, although such holograms have not yet been commercialized.


title: Holography

text: Holograms with x-rays are generated by using synchrotrons or x-ray free-electron lasers as radiation sources and pixelated detectors such as CCDs as recording medium. The reconstruction is then retrieved via computation. Due to the shorter wavelength of x-rays compared to visible light, this approach allows imaging objects with higher spatial resolution. As free-electron lasers can provide ultrashort and x-ray pulses in the range of femtoseconds which are intense and coherent, x-ray holography has been used to capture ultrafast dynamic processes.


title: Holography

text: Effects produced by lenticular printing, the Pepper's ghost illusion (or modern variants such as the Musion Eyeliner), tomography and volumetric displays are often confused with holograms. Such illusions have been called "fauxlography".


title: Holography

text: The Pepper's ghost technique, being the easiest to implement of these methods, is most prevalent in 3D displays that claim to be (or are referred to as) "holographic". While the original illusion, used in theater, involved actual physical objects and persons, located offstage, modern variants replace the source object with a digital screen, which displays imagery generated with 3D computer graphics to provide the necessary depth cues. The reflection, which seems to float mid-air, is still flat however, thus less realistic than if an actual 3D object was being reflected.


title: Holography

text: Examples of this digital version of Pepper's ghost illusion include the Gorillaz performances in the 2005 MTV Europe Music Awards and the 48th Grammy Awards; and Tupac Shakur's virtual performance at Coachella Valley Music and Arts Festival in 2012, rapping alongside Snoop Dogg during his set with Dr. Dre.


title: Holography

text: Swedish supergroup ABBA returned to the stage in May 2022, as digital avatars performing much-loved hits using technology which is an updated version of Pepper’s Ghost.


title: Holography

text: An even simpler illusion can be created by rear-projecting realistic images into semi-transparent screens. The rear projection is necessary because otherwise the semi-transparency of the screen would allow the background to be illuminated by the projection, which would break the illusion.


title: Holography

text: Crypton Future Media, a music software company that produced Hatsune Miku, one of many Vocaloid singing synthesizer applications, has produced concerts that have Miku, along with other Crypton Vocaloids, performing on stage as "holographic" characters. These concerts use rear projection onto a semi-transparent DILAD screen to achieve its "holographic" effect.


title: Holography

text: In 2011, in Beijing, apparel company Burberry produced the "Burberry Prorsum Autumn/Winter 2011 Hologram Runway Show", which included life size 2-D projections of models. The company's own video shows several centered and off-center shots of the main 2-dimensional projection screen, the latter revealing the flatness of the virtual models. The claim that holography was used was reported as fact in the trade media.


title: Holography

text: In Madrid, on 10 April 2015, a public visual presentation called "Hologramas por la Libertad" (Holograms for Liberty), featuring a ghostly virtual crowd of demonstrators, was used to protest a new Spanish law that prohibits citizens from demonstrating in public places. Although widely called a "hologram protest" in news reports, no actual holography was involved – it was yet another technologically updated variant of the Pepper's Ghost illusion.


title: Holography

text: Holography is distinct from specular holography which is a technique for making three-dimensional images by controlling the motion of specularities on a two-dimensional surface. It works by reflectively or refractively manipulating bundles of light rays, not by using interference and diffraction.


title: Holography

text: Holography has been widely referred to in movies, novels, and TV, usually in science fiction, starting in the late 1970s. Science fiction writers absorbed the urban legends surrounding holography that had been spread by overly-enthusiastic scientists and entrepreneurs trying to market the idea. This had the effect of giving the public overly high expectations of the capability of holography, due to the unrealistic depictions of it in most fiction, where they are fully three-dimensional computer projections that are sometimes tactile through the use of force fields. Examples of this type of depiction include the hologram of Princess Leia in "Star Wars", Arnold Rimmer from "Red Dwarf", who was later converted to "hard light" to make him solid, and the Holodeck and from "Star Trek".


title: Holography

text: Holography served as an inspiration for many video games with the science fiction elements. In many titles, fictional holographic technology has been used to reflect real life misrepresentations of potential military use of holograms, such as the "mirage tanks" in "" that can disguise themselves as trees. Player characters are able to use holographic decoys in games such as "" and "Crysis 2" to confuse and distract the enemy. "Starcraft" ghost agent Nova has access to "holo decoy" as one of her three primary abilities in "Heroes of the Storm."


title: Holography

text: Fictional depictions of holograms have, however, inspired technological advances in other fields, such as augmented reality, that promise to fulfill the fictional depictions of holograms by other means.


title: Celecoxib

text: Celecoxib, sold under the brand name Celebrex among others, is a COX-2 inhibitor and nonsteroidal anti-inflammatory drug (NSAID). It is used to treat the pain and inflammation in osteoarthritis, acute pain in adults, rheumatoid arthritis, ankylosing spondylitis, painful menstruation, and juvenile rheumatoid arthritis. It may also be used to decrease the risk of colorectal adenomas in people with familial adenomatous polyposis. It is taken by mouth. Benefits are typically seen within an hour.


title: Celecoxib

text: Common side effects include abdominal pain, nausea, and diarrhea. Serious side effects may include heart attacks, strokes, gastrointestinal perforation, gastrointestinal bleeding, kidney failure, and anaphylaxis. Use is not recommended in people at high risk for heart disease. The risks are similar to other NSAIDs, such as ibuprofen and naproxen. Use in the later part of pregnancy or during breastfeeding is not recommended.


title: Celecoxib

text: Celecoxib was patented in 1993 and came into medical use in 1999. It is available as a generic medication. In 2020, it was the 98th most commonly prescribed medication in the United States, with more than 7million prescriptions.


title: Celecoxib

text: Celecoxib is indicated for the treatment of osteoarthritis, rheumatoid arthritis, acute pain, musculoskeletal pain, painful menstruation, ankylosing spondylitis, juvenile rheumatoid arthritis, and to reduce the number of colon and rectal polyps in people with familial adenomatous polyposis. It may be used in children with juvenile rheumatoid arthritis who are older than two years of age and weigh more than 10 kg (22 lb).


title: Celecoxib

text: For postoperative pain, it is more or less equal to ibuprofen. For pain relief, it is similar to paracetamol (acetaminophen), which is the first line treatment for osteoarthritis.


title: Celecoxib

text: Evidence of effects are not clear as a number of studies done by the manufacturer have not been released for independent analysis.


title: Celecoxib

text: It has been used to reduce colon and rectal polyps in people with familial adenomatous polyposis, but it is not known if it decreases rates of cancer, so it is not a good choice for this reason.


title: Celecoxib

text: People with prior history of ulcer disease or GI bleeding require special precaution. Moderate to severe liver impairment or GI toxicity can occur with or without warning symptoms in people treated with NSAIDs.


title: Celecoxib

text: In October 2020, the U.S. Food and Drug Administration (FDA) required the drug label to be updated for all nonsteroidal anti-inflammatory medications to describe the risk of kidney problems in unborn babies that result in low amniotic fluid. They recommend avoiding NSAIDs in pregnant women at 20 weeks or later in pregnancy.


title: Celecoxib

text: Celecoxib contains a sulfonamide moiety and may cause allergic reactions in those allergic to other sulfonamide-containing drugs. This is in addition to the contraindication in people with severe allergies to other NSAIDs. However, it has a low (reportedly 4%) chance of inducing cutaneous reactions among persons who have a history of such reactions to aspirin or nonselective NSAIDs. NSAIDs may cause serious skin adverse events, including exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis; events may occur without warning and in patients without prior known sulfa allergy. Use should be discontinued at first sign of rash (or any other hypersensitivity).


title: Celecoxib

text: A 2013 meta-analysis of hundreds of clinical trials found that coxibs (the class of drugs that includes celecoxib) increase the risk of major cardiovascular problems by about 37% over placebo. In 2016, a randomized trial provided strong evidence that treatment with celecoxib is not more likely to result in poor cardiovascular outcomes than treatment with naproxen or ibuprofen. As a result, in 2018 an FDA advisory panel concluded that celecoxib poses no greater risk for causing heart attacks and strokes than the commonly-used NSAIDs ibuprofen or naproxen and recommended that the FDA consider changing its advice to physicians regarding celecoxib's safety.


title: Celecoxib

text: The COX-2 inhibitor rofecoxib (Vioxx) was removed from the market in 2004 due to its risk. Like all NSAIDs on the US market, celecoxib carries an FDA-mandated "black box warning" for cardiovascular and gastrointestinal risk. In February 2007, the American Heart Association warned that with respect to "patients with a prior history of or at high risk for cardiovascular disease... use of COX-2 inhibitors for pain relief should be limited to patients for whom there are no appropriate alternatives, and then, only in the lowest dose and for the shortest duration necessary."


title: Celecoxib

text: In 2005, a study published in the "Annals of Internal Medicine" found that cardiovascular effects of COX-2 inhibitors differ, depending on the drug. Other COX-2-selective inhibitors, such as rofecoxib, have significantly higher myocardial infarction rates than celecoxib. In April 2005, after an extensive review of data, the FDA concluded it was likely "that there is a 'class effect' for increased CV risk for all NSAIDs". In a 2006 meta-analysis of randomized control studies, the cerebrovascular events associated with COX-2 inhibitors were examined, but no significant risks were found when compared to nonselective NSAIDs or placebos.


title: Celecoxib

text: Celecoxib is predominantly metabolized by cytochrome P450 2C9. Caution must be exercised with concomitant use of 2C9 inhibitors, such as fluconazole, which can greatly elevate celecoxib serum levels. If used concomitantly with lithium, celecoxib increases lithium plasma levels. If used concomitantly with warfarin, celecoxib may result in increased risk of bleeding complications. The risk of bleeding and gastric ulcers also increase further when SSRIs are used in combination with celecoxib. The drug may increase the risk of kidney failure with angiotensin-converting enzyme-inhibitors, such as lisinopril, and diuretics, such as hydrochlorothiazide.


title: Celecoxib

text: In the US FDA's pregnancy categories, the drug is category C prior to 30 weeks gestation, and category D starting at 30 weeks gestation.


title: Celecoxib

text: A highly selective reversible inhibitor of the COX-2 isoform of cyclooxygenase, celecoxib inhibits the transformation of arachidonic acid to prostaglandin precursors. Therefore, it has analgesic and anti-inflammatory properties. Nonselective NSAIDs (such as aspirin, naproxen, and ibuprofen) inhibit both COX-1 and COX-2. Inhibition of COX-1 (which celecoxib does not inhibit at therapeutic concentrations) inhibits the production of prostaglandins and the production of thromboxane A2, a platelet activator. COX-1 is traditionally defined as a constitutively expressed "housekeeping" enzyme and plays a role in the protection of the gastrointestinal mucosa, kidney hemodynamics, and platelet thrombogenesis. COX-2, on the contrary, is extensively expressed in cells involved in inflammation and is upregulated by bacterial lipopolysaccharides, cytokines, growth factors, and tumor promoters. Celecoxib is approximately 10-20 times more selective for COX-2 inhibition over COX-1. It binds with its polar sulfonamide side chain to a hydrophilic side pocket region close to the active COX-2 binding site. In theory, this selectivity allows celecoxib and other COX-2 inhibitors to reduce inflammation (and pain) while minimizing gastrointestinal adverse drug reactions (e.g. stomach ulcers) that are common with nonselective NSAIDs.


title: Celecoxib

text: For its use in reducing colon polyps, celecoxib affects genes and pathways involved in inflammation and malignant transformation in tumors, but not normal tissues.


title: Celecoxib

text: The Searle research group found the two appropriately substituted aromatic rings must reside on adjacent positions about the central ring for adequate COX-2 inhibition. Various modifications can be made to the 1,5-diarylpyrazole moiety to deduce the structure-activity relationship of celecoxib. A para-sulfamoylphenyl at position 1 of the pyrazole was found to have a higher potency for COX-2 selective inhibition than a para-methoxyphenyl (see structures 1 and 2, below). In addition, a 4-(methylsulfonyl)phenyl or 4-sulfamoylphenyl is known to be necessary for COX-2 inhibition. For instance, replacing either of these entities with a –SONHCH substituent diminishes COX-2 inhibitory activity as noted with a very high inhibitory concentration-50 (see structures 3 – 5). At the 3-position of the pyrazole, a trifluoromethyl or difluoromethyl provides superior selectivity and potency compared to a fluoromethyl or methyl substitution (see structures 6 – 9).


title: Celecoxib

text: Celecoxib is compound 22; the 4-sulfamoylphenyl on the 1-pyrazol substituent is required for COX-2 inhibition and the 4-methyl on the 5-pyrazol system has low steric hindrance to maximize potency, while the 3-trifluoromethyl group provides superior selectivity and potency. To explain the selectivity of celecoxib, it is necessary to analyze the free energy of binding difference between the drug molecule and COX-1 compared to COX-2 enzymes. The structural modifications highlight the importance of binding to residue 523 in the side binding pocket of the cyclooxygenase enzyme, which is an isoleucine in COX-1 and a valine in COX-2. This mutation appears to contribute to COX-2 selectivity by creating steric hindrance between the sulfonamide oxygen and the methyl group of Ile523 that effectively destabilizes the celecoxib-COX-1 complex.


title: Celecoxib

text: It was initially marketed by Pfizer for arthritis. Celecoxib and other COX-2 selective inhibitors, valdecoxib, parecoxib, and mavacoxib, were discovered by a team at the Searle division of Monsanto led by John Talley.


title: Celecoxib

text: Two lawsuits arose over discovery of celecoxib. Daniel L. Simmons of Brigham Young University (BYU) discovered the COX-2 enzyme in 1988, and in 1991, BYU entered into a collaboration with Monsanto to develop drugs to inhibit it. Monsanto's pharmaceutical division was later purchased by Pfizer, and in 2006, BYU sued Pfizer for breach of contract, claiming Pfizer did not properly pay contractual royalties back to BYU. A settlement was reached in April 2012, in which Pfizer agreed to pay $450 million. Other important discoveries in COX-2 were made at University of Rochester, which patented the discoveries. When the patent issued, the university sued Searle (later Pfizer) in a case called, "University of Rochester v. G.D. Searle & Co.", 358 F.3d 916 (Fed. Cir. 2004). The court ruled in favor of Searle in 2004, holding in essence that the university had claimed a method requiring, yet provided no written description of, a compound that could inhibit COX-2 and therefore the patent was invalid.


title: Celecoxib

text: According to the National Academy of Sciences, Philip Needleman, who was vice president of Monsanto in 1989 and president of Searle in 1993 oversaw research into COX-2 that led to the development of the anti-inflammatory drug celecoxib (Celebrex). He became senior executive vice president and chief scientist of Pharmacia from 2000 to 2003. Celecoxib was discovered and developed by G. D. Searle & Company and was approved by the FDA on 31 December 1998. It was co-promoted by Monsanto Company (parent company of Searle) and Pfizer under the brand name Celebrex. Monsanto merged with Pharmacia, from which the Medical Research Division was acquired by Pfizer, giving Pfizer ownership of Celebrex. The drug was at the core of a major patent dispute that was resolved in Searle's favor (later Pfizer) in 2004. In "University of Rochester v. G.D. Searle & Co.", 358 F.3d 916 (Fed. Cir. 2004), the University of Rochester claimed that United States Pat. No. 6,048,850 (which claimed a method of inhibiting COX-2 in humans using a compound, without actually disclosing what that compound might be) covered drugs such as celecoxib. The court ruled in favor of Searle, holding in essence that the university had claimed a method requiring, yet provided no written description of, a compound that could inhibit COX-2 and therefore the patent was invalid.


title: Celecoxib

text: After the withdrawal of rofecoxib from the market in September 2004, celecoxib enjoyed a robust increase in sales. However, the results of the APC trial in December of that year raised concerns that Celebrex might carry risks similar to those of rofecoxib, and Pfizer announced a moratorium on direct-to-consumer advertising of Celebrex soon afterwards. Sales reached $2 billion in 2006. Prior to its availability in generic form, it was one of Pfizer's "best-selling drugs, amounting to more than $2.5 billion in sales [by 2012], and was prescribed to 2.4 million" people in 2011. By 2012, 33 million Americans had taken celecoxib.


title: Celecoxib

text: Pfizer resumed advertising Celebrex in magazines in 2006, and resumed television advertising in April 2007 with an unorthodox, -minute advertisement which extensively discussed the adverse effects of Celebrex in comparison with other anti-inflammatory drugs. The ad drew criticism from the consumer advocacy group Public Citizen, which called the ad's comparisons misleading. Pfizer responded to Public Citizen's concerns with assurances that they are truthfully advertising the risk and benefits of Celebrex as set forth by the FDA.


title: Celecoxib

text: Pfizer and its partner, Pharmacia presented findings from their study that Celebrex was "better in protecting the stomach from serious complications than other drugs." This became Celebrex's main selling point. However, following federal investigations it was revealed that Pfizer and Pharmacia "only presented the results from the first six months of a year long study rather than the whole thing." These partial results were then published in The Journal of the American Medical Association. In 2001, the US Food and Drug Administration (FDA) released the full results of the Pfizer and Pharmacia study which showed that they had withheld crucial data. By 2012, a federal judge unsealed "thousands of pages of internal documents and depositions" in a "long-running securities fraud case against Pfizer."


title: Celecoxib

text: On 11 March 2009, Scott S. Reuben, former chief of acute pain at Baystate Medical Center, Springfield, Massachusetts, revealed that the data for 21 studies he had authored for the efficacy of the drug (along with others such as Vioxx) had been fabricated. The analgesic effects of the drugs had been exaggerated. Reuben was also a former paid spokesperson for Pfizer. Although from 2002 to 2007 Pfizer underwrote much of Dr. Reuben's research and "many of his trials found that Celebrex and Lyrica, Pfizer drugs, were effective against postoperative pain," Pfizer was not aware of the fraudulent data. None of the retracted studies were submitted to either the US Food and Drug Administration or the European Union's regulatory agencies prior to the drug's approval. Although Pfizer issued a public statement declaring, "It is very disappointing to learn about Dr. Scott Reuben's alleged actions. When we decided to support Dr. Reuben's research, he worked for a credible academic medical center and appeared to be a reputable investigator", the documents unsealed in 2012, revealed that by February 2000, Pharmacia employees had devised a strategy to present the findings.


title: Celecoxib

text: Pfizer markets celecoxib under the brand name Celebrex, and it is available as oral capsules containing 50, 100, 200 or 400 mg of celecoxib.


title: Celecoxib

text: It is legally available in many jurisdictions as a generic under several brand names. In the US, celecoxib was covered by three patents, two of which expired on 30 May 2014, and one of which (US RE44048) was due to expire 2 December 2015. On 13 March 2014, that patent was found to be invalid for double patenting. Upon the patent expiry on 30 May 2014, the FDA approved the first versions of generic celecoxib.


title: Celecoxib

text: On the theory that inflammation plays a role in the pathogenesis of major mental disorders, celecoxib has been trialed for a number of psychiatric disorders, including major depression, bipolar disorder, and schizophrenia.


title: Celecoxib

text: A meta-analysis considering trials of celecoxib as an adjunctive treatment in bipolar disorder was inconclusive citing low evidence quality.


title: Celecoxib

text: It has been used to reduce colon and rectal polyps in people with familial adenomatous polyposis, but it is not known if it decreases rates of cancer, so it is not a good choice for this reason.


title: Celecoxib

text: The use of celecoxib to reduce the risk of colorectal cancer has been investigated, but neither celecoxib nor any other drug is indicated for this use. Small-scale clinical trials in very high-risk people (belonging to FAP families) showed celecoxib can prevent polyp growth. Hence, large-scale randomized clinical trials were undertaken. Results show a 33 to 45% polyp recurrence reduction in people treated with celecoxib each day. However, serious cardiovascular events were significantly more frequent in the celecoxib-treated groups. Aspirin shows a similar (and possibly larger) protective effect, has demonstrated cardioprotective effects and is significantly cheaper, but no head-to-head clinical trials have compared the two drugs.


title: Celecoxib

text: Different from cancer prevention, cancer treatment is focused on the therapy of tumors that have already formed and have established themselves inside the patient. Many studies are going on to determine whether celecoxib might be useful for this latter condition. However, during molecular studies in the laboratory, it became apparent that celecoxib could interact with other intracellular components besides its most famous target, COX-2. The discovery of these additional targets has generated much controversy, and the initial assumption that celecoxib reduces tumor growth primarily by the inhibition of COX-2 became contentious.


title: Celecoxib

text: Certainly, the inhibition of COX-2 is paramount for the anti-inflammatory and analgesic function of celecoxib. However, whether inhibition of COX-2 also plays a dominant role in this drug's anticancer effects is unclear. For example, a recent study with malignant tumor cells showed celecoxib could inhibit the growth of these cells "in vitro", but COX-2 played no role in this outcome; even more strikingly, the anticancer effects of celecoxib were also obtained with the use of cancer cell types that do not even contain COX-2. Karen Seibert and colleagues have published research showing antiangiogenic and antitumor activity of celecoxib in animal models.


title: Celecoxib

text: Additional support for the idea that other targets besides COX-2 are important for celecoxib's anticancer effects has come from studies with chemically modified versions of celecoxib. Several dozen analogs of celecoxib were generated with small alterations in their chemical structures. Some of these analogs retained COX-2 inhibitory activity, whereas many others did not. However, when the ability of all these compounds to kill tumor cells in cell culture was investigated, the antitumor potency did not at all depend on whether or not the respective compound could inhibit COX-2, showing the inhibition of COX-2 was not required for the anticancer effects. One of these compounds, 2,5-dimethyl-celecoxib, which entirely lacks the ability to inhibit COX-2, actually displayed stronger anticancer activity than celecoxib.


title: Lou Gramm

text: Lou Gramm (born Louis Andrew Grammatico; 2 May 1950) is an American singer-songwriter, best known for being the lead singer of the rock band Foreigner from 1977 to 1990 and 1992 to 2003 during which time the band had numerous successful albums and singles.


title: Lou Gramm

text: Louis Andrew Grammatico was born on 2 May 1950, in Rochester, New York, the son of Nikki (née Masetta), a singer, and Bennie Grammatico, a band leader and trumpeter. He attended Gates-Chili High School in Rochester, graduating with the class of 1968, and majored in education and art at Monroe Community College.


title: Lou Gramm

text: Gramm became front man for the band Black Sheep. Black Sheep was the first American band signed to the Chrysalis label, which released their first single, "Stick Around" (1974). Soon after this initial bit of success, Black Sheep signed with Capitol Records, releasing two albums in succession: "Black Sheep" (1975) and "Encouraging Words" (late 1975). They were the opening act for Kiss when an accident with their equipment truck on the ice-covered New York State Thruway suddenly ended the band's tour on Christmas Eve, 1975. Unable to support its albums with live performances, Black Sheep disbanded.


title: Lou Gramm

text: A year earlier, Gramm met his future bandmate Mick Jones. Jones was in Rochester performing with the band Spooky Tooth, and Gramm had given Jones a copy of Black Sheep's first album ("S/T"). It was early in 1976, not long after Black Sheep's truck accident, when Jones, in search of a lead singer for a new band he was assembling, expressed his interest in Gramm and invited him to audition.


title: Lou Gramm

text: Gramm traveled to New York to audition and got the job. Lou Grammatico then became Lou Gramm. The band, which was initially known as "Trigger," was later renamed Foreigner. With Foreigner, Gramm became one of the most successful rock vocalists of the late 1970s and 1980s.


title: Lou Gramm

text: Foreigner's first eight singles cracked the Billboard Top 20, making them the first band since The Beatles to achieve this milestone. Gramm performed vocals on all of Foreigner's hits including "Urgent", "Juke Box Hero", "Break It Up", "Say You Will", and "I Don't Want to Live Without You". He co-wrote most of the band's songs, including the hit ballads "Waiting for a Girl Like You", which spent ten weeks at #2 on the 1981/82 American Hot 100, and "I Want to Know What Love Is", which was a number one hit in eight countries.


title: Lou Gramm

text: Gramm and Jones had a volatile chemistry. Gramm wanted the band to remain true to its purer rock origins, favoring music with a solid drum and guitar structure, whereas Jones embraced the 1980s style of synthesizer ballads. Gramm has called the "4" album (1981) the high point of his work with Foreigner. Foreigner's next album, "Agent Provocateur" (1984), took three years to release due to the ongoing creative differences between Jones and Gramm. The band released "Inside Information" in 1987.


title: Lou Gramm

text: Gramm released his first solo album, "Ready or Not", in January 1987 to critical acclaim. The single "Midnight Blue" reached the top five.


title: Lou Gramm

text: Also in 1987, Gramm contributed the song "Lost in the Shadows" to the soundtrack for the comedy horror film "The Lost Boys".


title: Lou Gramm

text: A second solo effort, "Long Hard Look" (October 1989), that included the top ten hit "Just Between You and Me" as well as "True Blue Love", reached the Top 40. The album also included "Hangin' on My Hip", which was featured in the 1990 film "Navy SEALs".


title: Lou Gramm

text: Gramm announced his departure from Foreigner in May 1990 due to differences with Jones, and to focus on his solo career.


title: Lou Gramm

text: Gramm also formed Shadow King with close friend and former Black Sheep bassist Bruce Turgon; their 1991 self-titled album was released by Atlantic Records. Despite positive reviews, the group did not enjoy the level of marketing and promotional support necessary to sustain a new project and soon disbanded. Also in 1991, Gramm contributed the song "One Dream" to the movie "".


title: Lou Gramm

text: Gramm rejoined Foreigner in May 1992 after working out his differences with Jones during the Los Angeles riots. In 1995, Foreigner released the album "Mr. Moonlight" on the Rhythm Safari label which, although relatively successful in Europe, was not as widely marketed or distributed in the U.S. Still, "Until the End of Time" made inroads at adult contemporary radio, peaking at number 8.


title: Lou Gramm

text: In 1996, Jones invited Gramm to perform backing vocals on a cover version of "I Want to Know What Love Is" he was producing for the Australian singer Tina Arena. The song went on to become a major hit again throughout Europe.


title: Lou Gramm

text: In April 1997, on the eve of a Japan tour, Gramm was diagnosed with a benign brain tumor and underwent surgery. He continued to work with Jones throughout his illness. By 1998, Gramm was back touring with Foreigner.


title: Lou Gramm

text: Gramm was inducted to the Songwriters Hall of Fame on 13 June 2013. On 20 July 2017, Gramm joined Foreigner for three songs during an encore at Jones Beach Theatre in Long Island, New York. On 29 December 2018, Gramm announced on stage in Schenectady, New York that he was retiring from touring. However, he stated that he would continue to release studio music and perform occasional live shows including The Lopen, a celebrity concert produced by Howard Perl Entertainment to benefit children at Akron Children's Hospital.


title: Lou Gramm

text: In 2019, Gramm toured on a bill with Asia Featuring John Payne, where they also acted as his back-up group. Gramm performed lead vocals on the track "Sometimes" on the 2019 album "The Secret" by Alan Parsons.


title: Lou Gramm

text: Gramm told RockBandReviews.com in 2019 that he was planning to release some new solo material later that year. "I'm working on some things now that were extra songs on my solo albums," he said. "If there's 10 songs on the album, you usually record 13 and pick the best 10, or the 10 that are finished. So the other three have been siting around for 25, 30 years, and I went back recently and listened to them, and they sounded so good that I finished them. Starting in about two months, maybe three months, I'm gonna be releasing three songs on downloads and see how that works out. So those songs will be heard for the first time. And then in another three or four months, there's gonna be three more new songs released. So that could be going on for six or eight months, and we'll see what happens."


title: Lou Gramm

text: Gramm also said that he is "thinking about" releasing a greatest-hits package of his non-Foreigner works.


title: Lou Gramm

text: In 1992, Gramm, after having completed a stint in drug rehabilitation, became a born again Christian.


title: Lou Gramm

text: In April 1997, Gramm was diagnosed with a type of brain tumor called a craniopharyngioma. Although the tumor was benign, the resulting surgery damaged his pituitary gland. In addition, the recovery program had caused Gramm to gain weight, and likewise affected his stamina and voice.


title: Lou Gramm

text: Along with his love for music, he developed an affinity for fast cars. In Rochester in the late 1960s and early '70s, Gramm remembers, it wasn't difficult to find a summer night drag race. Gramm's vehicle of choice: A Chevy Nova 396, 375-horsepower, factory-printed.


title: Lou Gramm

text: As of 2017, Gramm is married to Robyn Grammatico. They have a daughter. He also has four children from previous marriages.


title: Swift (programming language)

text: Swift is a general-purpose, multi-paradigm, compiled programming language developed by Apple Inc. and the open-source community. First released in 2014, Swift was developed as a replacement for Apple's earlier programming language Objective-C, as Objective-C had been largely unchanged since the early 1980s and lacked modern language features. Swift works with Apple's Cocoa and Cocoa Touch frameworks, and a key aspect of Swift's design was the ability to interoperate with the huge body of existing Objective-C code developed for Apple products over the previous decades. It was built with the open source LLVM compiler framework and has been included in Xcode since version 6, released in 2014. On Apple platforms, it uses the Objective-C runtime library, which allows C, Objective-C, C++ and Swift code to run within one program.


title: Swift (programming language)

text: Apple intended Swift to support many core concepts associated with Objective-C, notably dynamic dispatch, widespread late binding, extensible programming and similar features, but in a "safer" way, making it easier to catch software bugs; Swift has features addressing some common programming errors like null pointer dereferencing and provides syntactic sugar to help avoid the pyramid of doom. Swift supports the concept of protocol extensibility, an extensibility system that can be applied to types, structs and classes, which Apple promotes as a real change in programming paradigms they term "protocol-oriented programming" (similar to traits).


title: Swift (programming language)

text: Swift was introduced at Apple's 2014 Worldwide Developers Conference (WWDC). It underwent an upgrade to version 1.2 during 2014 and a major upgrade to Swift 2 at WWDC 2015. Initially a proprietary language, version 2.2 was made open-source software under the Apache License 2.0 on December 3, 2015, for Apple's platforms and Linux.


title: Swift (programming language)

text: Through version 3.0 the syntax of Swift went through significant evolution, with the core team making source stability a focus in later versions. In the first quarter of 2018 Swift surpassed Objective-C in measured popularity.


title: Swift (programming language)

text: Swift 4.0, released in 2017, introduced several changes to some built-in classes and structures. Code written with previous versions of Swift can be updated using the migration functionality built into Xcode. Swift 5, released in March 2019, introduced a stable binary interface on Apple platforms, allowing the Swift runtime to be incorporated into Apple operating systems. It is source compatible with Swift 4.


title: Swift (programming language)

text: Swift 5.1 was officially released in September 2019. Swift 5.1 builds on the previous version of Swift 5 by extending the stable features of the language to compile-time with the introduction of module stability. The introduction of module stability makes it possible to create and share binary frameworks that will work with future releases of Swift.


title: Swift (programming language)

text: Swift 5.5, officially announced by Apple at the 2021 WWDC, significantly expands language support for concurrency and asynchronous code, notably introducing a unique version of the actor model.


title: Swift (programming language)

text: Development of Swift started in July 2010 by Chris Lattner, with the eventual collaboration of many other programmers at Apple. Swift took language ideas "from Objective-C, Rust, Haskell, Ruby, Python, C#, CLU, and far too many others to list". On June 2, 2014, the Apple Worldwide Developers Conference (WWDC) application became the first publicly released app written with Swift. A beta version of the programming language was released to registered Apple developers at the conference, but the company did not promise that the final version of Swift would be source code compatible with the test version. Apple planned to make source code converters available if needed for the full release.


title: Swift (programming language)

text: "The Swift Programming Language", a free 500-page manual, was also released at WWDC, and is available on the Apple Books Store and the official website.


title: Swift (programming language)

text: Swift reached the 1.0 milestone on September 9, 2014, with the "Gold Master" of Xcode 6.0 for iOS. Swift 1.1 was released on October 22, 2014, alongside the launch of Xcode 6.1. Swift 1.2 was released on April 8, 2015, along with Xcode 6.3. Swift 2.0 was announced at WWDC 2015, and was made available for publishing apps in the App Store on September 21, 2015. Swift 3.0 was released on September 13, 2016. Swift 4.0 was released on September 19, 2017. Swift 4.1 was released on March 29, 2018.


title: Swift (programming language)

text: Swift won first place for "Most Loved Programming Language" in the Stack Overflow Developer Survey 2015 and second place in 2016.


title: Swift (programming language)

text: On December 3, 2015, the Swift language, supporting libraries, debugger, and package manager were open-sourced under the Apache 2.0 license with a Runtime Library Exception, and Swift.org was created to host the project. The source code is hosted on GitHub, where it is easy for anyone to get the code, build it themselves, and even create pull requests to contribute code back to the project.


title: Swift (programming language)

text: In December 2015, IBM announced its Swift Sandbox website, which allows developers to write Swift code in one pane and display output in another. The Swift Sandbox was deprecated in January 2018.


title: Swift (programming language)

text: During the WWDC 2016, Apple announced an iPad exclusive app, named Swift Playgrounds, intended to teach people how to code in Swift. The app is presented in a 3D video game-like interface which provides feedback when lines of code are placed in a certain order and executed.


title: Swift (programming language)

text: In January 2017, Chris Lattner announced his departure from Apple for a new position with Tesla Motors, with the Swift project lead role going to team veteran Ted Kremenek.


title: Swift (programming language)

text: During WWDC 2019, Apple announced SwiftUI with Xcode 11, which provides a framework for declarative UI structure design across all Apple platforms.


title: Swift (programming language)

text: Official downloads for the Ubuntu distribution of Linux have been available since Swift 2.2, with more distros added since Swift 5.2.4, CentOS and Amazon Linux. There is an unofficial SDK and native toolchain package for Android too.


title: Swift (programming language)

text: The platforms Swift supports are Apple's operating systems (Darwin, iOS, iPadOS, macOS, tvOS, watchOS), Linux, Windows, and Android.


title: Swift (programming language)

text: Swift is an alternative to the Objective-C language that employs modern programming-language theory concepts and strives to present a simpler syntax. During its introduction, it was described simply as "Objective-C without the baggage of C".


title: Swift (programming language)

text: By default, Swift does not expose pointers and other unsafe accessors, in contrast to Objective-C, which uses pointers pervasively to refer to object instances. Also, Objective-C's use of a Smalltalk-like syntax for making method calls has been replaced with a dot-notation style and namespace system more familiar to programmers from other common object-oriented (OO) languages like Java or C#. Swift introduces true named parameters and retains key Objective-C concepts, including protocols, closures and categories, often replacing former syntax with cleaner versions and allowing these concepts to be applied to other language structures, like enumerated types (enums).


title: Swift (programming language)

text: Swift supports closures (known as lambdas in other languages). Closures are self-contained blocks of functionality that can be passed around and used in code, and can also be used as anonymous functions. Here are some examples:


title: Swift (programming language)

text: Under the Cocoa and Cocoa Touch environments, many common classes were part of the Foundation Kit library. This included the NSString string library (using Unicode, UTF-8 in Swift 5, changed from UTF-16), the NSArray and NSDictionary collection classes, and others. Objective-C provided various bits of syntactic sugar to allow some of these objects to be created on-the-fly within the language, but once created, the objects were manipulated with object calls. For instance, in Objective-C concatenating two NSStrings required method calls similar to this:


title: Swift (programming language)

text: str = [str stringByAppendingString:@" world"]; In Swift, many of these basic types have been promoted to the language's core, and can be manipulated directly. For instance, strings are invisibly bridged to NSString (when Foundation is imported) and can now be concatenated with the codice_2 operator, allowing greatly simplified syntax; the prior example becoming:


title: Swift (programming language)

text: Swift supports five access control levels for symbols: , , , , and . Unlike many object-oriented languages, these access controls ignore inheritance hierarchies: indicates that a symbol is accessible only in the immediate scope, indicates it is accessible only from within the file, indicates it is accessible within the containing module, indicates it is accessible from any module, and (only for classes and their methods) indicates that the class may be subclassed outside of the module.


title: Swift (programming language)

text: An important new feature in Swift is option types, which allow references or values to operate in a manner similar to the common pattern in C, where a pointer may refer to a value or may be null. This implies that non-optional types cannot result in a null-pointer error; the compiler can ensure this is not possible.


title: Swift (programming language)

text: Optional types are created with the codice_3 mechanism—to make an Integer that is nullable, one would use a declaration similar to codice_4. As in C#, Swift also includes syntactic sugar for this, allowing one to indicate a variable is optional by placing a question mark after the type name, codice_5. Variables or constants that are marked optional either have a value of the underlying type or are codice_6. Optional types "wrap" the base type, resulting in a different instance. codice_7 and codice_8 are fundamentally different types, the latter has more in common with codice_9 than codice_7.


title: Swift (programming language)

text: To access the value inside, assuming it is not nil, it must be "unwrapped" to expose the instance inside. This is performed with the codice_11 operator:


title: Swift (programming language)

text: In this case, the codice_11 operator unwraps codice_13 to expose the instance inside, allowing the method call to be made on it. If codice_13 is nil, a null-pointer error occurs. This can be annoying in practice, so Swift also includes the concept of optional chaining to test whether the instance is nil and then unwrap it if it is non-null:


title: Swift (programming language)

text: In this case the runtime calls codice_15 only if codice_13 is not nil, suppressing the error. Normally this requires the programmer to test whether codice_17 is nil before proceeding. The origin of the term "chaining" comes from the more common case where several method calls/getters are chained together. For instance:


title: Swift (programming language)

text: Swift 2 introduced the new keyword codice_1 for cases in which code should stop executing if some condition is unmet:


title: Swift (programming language)

text: Using codice_1 has three benefits. While the syntax can act as an codice_21 statement, its primary benefit is inferring non-nullability. Where an codice_21 statement requires a case, codice_1 assumes the case based on the condition provided. Also, since codice_1 contains no scope, with exception of the codice_25 closure, codice_26 is presented as an unwrapped optional to the guard's super-scope. Lastly, if the codice_1 statement's test fails, Swift requires the codice_25 to exit the current method or loop, ensuring codice_26 never is accessed when codice_6. This is performed with the keywords codice_31, codice_32, codice_33, or codice_34, or by calling a function returning a codice_35 (e.g. codice_36).


title: Swift (programming language)

text: Objective-C was weakly typed and allowed any method to be called on any object at any time. If the method call failed, there was a default handler in the runtime that returned nil. That meant that no unwrapping or testing was needed, the equivalent statement in Objective-C:


title: Swift (programming language)

text: Would return nil, and this could be tested. However, this also demanded that all method calls be dynamic, which introduces significant overhead. Swift's use of optionals provides a similar mechanism for testing and dealing with nils, but does so in a way that allows the compiler to use [[static dispatch]] because the unwrapping action is called on a defined instance (the wrapper), versus occurring in the runtime dispatch system.


title: Swift (programming language)

text: In many object-oriented languages, objects are represented internally in two parts. The object is stored as a block of data placed on the [[Heap (data structure)|heap]], while the name (or "handle") to that object is represented by a [[Pointer (computer programming)|pointer]]. Objects are passed between methods by copying the value of the pointer, allowing the same underlying data on the heap to be accessed by anyone with a copy. In contrast, basic types like integers and floating-point values are represented directly; the handle contains the data, not a pointer to it, and that data is passed directly to methods by copying. These styles of access are termed "pass-by-reference" in the case of objects, and "pass-by-value" for basic types.


title: Swift (programming language)

text: Both concepts have their advantages and disadvantages. Objects are useful when the data is large, like the description of a window or the contents of a document. In these cases, access to that data is provided by copying a 32- or 64-bit value, versus copying an entire data structure. However, smaller values like integers are the same size as pointers (typically both are one [[Word (computer architecture)|word]]), so there is no advantage to passing a pointer, versus passing the value. Also, pass-by-reference inherently requires a dereferencing operation, which can produce noticeable overhead in some operations, typically those used with these basic value types, like mathematics.


title: Swift (programming language)

text: Similarly to C# and in contrast to most other OO languages, Swift offers built-in support for objects using either pass-by-reference or pass-by-value semantics, the former using the codice_37 declaration and the latter using codice_38. Structs in Swift have almost all the same features as classes: methods, implementing protocols and using the extension mechanisms. For this reason, Apple terms all data generically as "instances", versus objects or values. Structs do not support inheritance, however.


title: Swift (programming language)

text: The programmer is free to choose which semantics are more appropriate for each data structure in the application. Larger structures like windows would be defined as classes, allowing them to be passed around as pointers. Smaller structures, like a 2D point, can be defined as structs, which will be pass-by-value and allow direct access to their internal data with no dereference. The performance improvement inherent to the pass-by-value concept is such that Swift uses these types for almost all common data types, including codice_39 and codice_40, and types normally represented by objects, like codice_7 and codice_42. Using value types can result in significant performance improvements in user applications as well.


title: Swift (programming language)

text: To ensure that even the largest structs do not cause a performance penalty when they are handed off, Swift uses [[copy on write]] so that the objects are copied only if and when the program attempts to change a value in them. This means that the various accessors have what is in effect a pointer to the same data storage. So while the data is physically stored as one instance in memory, at the level of the application, these values are separate and physical separation is enforced by copy on write only if needed.


title: Swift (programming language)

text: A key feature of Objective-C is its support for "categories", methods that can be added to extend classes at runtime. Categories allow extending classes in-place to add new functions with no need to subclass or even have access to the original [[source code]]. An example might be to add [[spell checker]] support to the base codice_43 class, which means all instances of NSString in the application gain spell checking. The system is also widely used as an organizational technique, allowing related code to be gathered into library-like extensions. Swift continues to support this concept, although they are now termed "extensions", and declared with the keyword codice_44. Unlike Objective-C, Swift can also add new properties accessors, types, and enums to extant instances .


title: Swift (programming language)

text: Another key feature of Objective-C is its use of [[Protocol (object-oriented programming)|"protocols"]], known in most modern languages as "interfaces". Protocols promise that a particular class implements a set of methods, meaning that other objects in the system can call those methods on any object supporting that protocol. This is often used in modern OO languages as a substitute for [[multiple inheritance]], although the feature sets are not entirely similar. A common example of a protocol in Cocoa is the codice_45 protocol, which defines one method, codice_46, that implements [[object copying#deep copy|deep copying]] on objects.


title: Swift (programming language)

text: In Objective-C, and most other languages implementing the protocol concept, it is up to the programmer to ensure that the required methods are implemented in each class. Swift adds the ability to add these methods using extensions, and to use [[generic programming]] (generics) to implement them. Combined, these allow protocols to be written once and support a wide variety of instances. Also, the extension mechanism can be used to add protocol conformance to an object that does not list that protocol in its definition.


title: Swift (programming language)

text: For example, a protocol might be declared called codice_47, which ensures that instances that conform to the protocol implement a codice_48 method that returns a codice_7. In Swift, this can be declared with code like this:


title: Swift (programming language)

text: In Swift, like many modern languages supporting interfaces, protocols can be used as types, which means variables and methods can be defined by protocol instead of their specific type:


title: Swift (programming language)

text: It does not matter what sort of instance codice_50 is, the compiler will ensure that it conforms to the protocol and thus this code is safe. This syntax also means that collections can be based on protocols also, like codice_51.


title: Swift (programming language)

text: As Swift treats structs and classes as similar concepts, both extensions and protocols are extensively used in Swift's runtime to provide a rich API based on structs. For instance, Swift uses an extension to add the codice_52 protocol to many of their basic types, like Strings and Arrays, allowing them to be compared with the codice_53 operator. A concrete example of how all of these features interact can be seen in the concept of "default protocol implementations":


title: Swift (programming language)

text: This function defines a method that works on any instance conforming to codice_52, providing a "not equals" function. Any instance, class or struct, automatically gains this implementation simply by conforming to codice_52. As many instances gain codice_52 through their base implementations or other generic extensions, most basic objects in the runtime gain equals and not equals with no code.


title: Swift (programming language)

text: This combination of protocols, defaults, protocol inheritance, and extensions allows many of the functions normally associated with classes and inheritance to be implemented on value types. Properly used, this can lead to dramatic performance improvements with no significant limits in API. This concept is so widely used within Swift that Apple has begun calling it a "protocol-oriented programming language". They suggest addressing many of the problem domains normally solved through classes and inheritance using protocols and structs instead.


title: Swift (programming language)

text: On Apple systems, Swift uses the same runtime as the extant [[Objective-C]] system, but requires iOS 7 or macOS 10.9 or higher. It also depends on [[Grand Central Dispatch]]. Swift and Objective-C code can be used in one program, and by extension, C and C++ also. In contrast to C, [[C++]] code cannot be used directly from Swift. An Objective-C or C wrapper must be created between Swift and C++. In the case of Objective-C, Swift has considerable access to the object model, and can be used to subclass, extend and use Objective-C code to provide protocol support. The converse is not true: a Swift class cannot be subclassed in Objective-C.


title: Swift (programming language)

text: To aid development of such programs, and the re-use of extant code, Xcode 6 and higher offers a semi-automated system that builds and maintains a "bridging header" to expose Objective-C code to Swift. This takes the form of an additional [[header file]] that simply defines or imports all of the Objective-C symbols that are needed by the project's Swift code. At that point, Swift can refer to the types, functions, and variables declared in those imports as though they were written in Swift. Objective-C code can also use Swift code directly, by importing an automatically maintained header file with Objective-C declarations of the project's Swift symbols. For instance, an Objective-C file in a mixed project called "MyApp" could access Swift classes or functions with the code codice_57. Not all symbols are available through this mechanism, however—use of Swift-specific features like generic types, non-object optional types, sophisticated enums, or even Unicode identifiers may render a symbol inaccessible from Objective-C.


title: Swift (programming language)

text: Swift also has limited support for "attributes", metadata that is read by the development environment, and is not necessarily part of the compiled code. Like Objective-C, attributes use the codice_58 syntax, but the currently available set is small. One example is the codice_59 attribute, which marks a given value in the code as an "outlet", available for use within [[Interface Builder]] (IB). An "outlet" is a device that binds the value of the on-screen display to an object in code.


title: Swift (programming language)

text: On non-Apple systems, Swift does not depend on an Objective-C runtime or other Apple system libraries; a set of Swift "Corelib" implementations replace them. These include a "swift-corelibs-foundation" to stand in for the [[Foundation Kit]], a "swift-corelibs-libdispatch" to stand in for the Grand Central Dispatch, and an "swift-corelibs-xctest" to stand in for the XCTest APIs from [[Xcode]].


title: Swift (programming language)

text: As of 2019, with Xcode 11, Apple has also added a major new UI paradigm called SwiftUI. SwiftUI replaces the older [[Interface Builder]] paradigm with a new declarative development paradigm.


title: Swift (programming language)

text: Swift uses [[Automatic Reference Counting]] (ARC) to [[Memory management|manage memory]]. Apple used to require manual memory management in Objective-C, but introduced ARC in 2011 to allow for easier memory allocation and deallocation. One problem with ARC is the possibility of creating a "[[Reference counting#reference cycle|strong reference cycle]]", where objects reference each other in a way that you can reach the object you started from by following references (e.g. A references B, B references A). This causes them to become leaked into memory as they are never released. Swift provides the keywords codice_60 and codice_61 to prevent strong reference cycles. Typically a parent-child relationship would use a strong reference while a child-parent would use either codice_60 reference, where parents and children can be unrelated, or codice_61 where a child always has a parent, but parent may not have a child. Weak references must be optional variables, since they can change and become codice_6.


title: Swift (programming language)

text: A closure within a class can also create a strong reference cycle by capturing self references. Self references to be treated as weak or unowned can be indicated using a "capture list."


title: Swift (programming language)

text: A key element of the Swift system is its ability to be cleanly debugged and run within the development environment, using a [[read–eval–print loop]] (REPL), giving it interactive properties more in common with the scripting abilities of Python than traditional [[system programming]] languages. The REPL is further enhanced with [[Swift Playgrounds|playgrounds]], interactive views running within the Xcode environment that respond to code or debugger changes on-the-fly. Playgrounds allow programmers to add in Swift code along with markdown documentation. If some code changes over time or with regard to some other ranged input value, the view can be used with the Timeline Assistant to demonstrate the output in an animated way. In addition, Xcode has debugging features for Swift development including breakpoints, step through and step over statements, as well as UI element placement breakdowns for app developers.


title: Swift (programming language)

text: Apple says that Swift is "an industrial-quality programming language that's as expressive and enjoyable as a scripting language".


title: Swift (programming language)

text: Many of the features introduced with Swift have well-known performance and safety trade-offs. Apple has implemented [[Optimizing compiler|optimizations]] that reduce this overhead.


title: Swift (programming language)

text: Swift is considered a [[List of C-family programming languages|C family programming language]] and is similar to C in various ways:


title: Swift (programming language)

text: Since the language is open-source, there are prospects of it being ported to the web. Some web frameworks have already been developed, such as [[IBM]]'s [[Kitura]], [[Perfect (server framework)|Perfect]] and [[Vapor (Server-side Swift)|Vapor]].


title: Swift (programming language)

text: An official "Server APIs" work group has also been started by Apple, with members of the Swift developer community playing a central role.


title: Swift (programming language)

text: A second free implementation of Swift that targets [[Cocoa (API)|Cocoa]], [[Microsoft]]'s [[Common Language Infrastructure]] ([[.NET Framework|.NET]]), and the [[Java (software platform)|Java]] and [[Android (operating system)|Android]] platform exists as part of the "Elements Compiler" from [[RemObjects Software]].


title: Swift (programming language)

text: By combining [[toolchain]]s from LLVM and [[Macintosh Programmer's Workshop]], it is possible to run a very small subset of the language on [[Mac OS 9]].


title: Executive (government)

text: The executive (short for executive branch or executive power) is the part of government that enforces law, and has responsibility for the governance of a state.


title: Executive (government)

text: In political systems based on the principle of separation of powers, authority is distributed among several branches (executive, legislative, judicial)—an attempt to prevent the concentration of power in the hands of a single group of people. In such a system, the executive does not pass laws (the role of the legislature) or interpret them (the role of the judiciary). Instead, the executive enforces the law as written by the legislature and interpreted by the judiciary. The executive can be the source of certain types of law, such as a decree or executive order. Executive bureaucracies are commonly the source of regulations.


title: Executive (government)

text: In political systems that use fusion of powers, which typically includes parliamentary systems, only the executive is typically referred to as the government (with the legislature often referred to as "Parliament" or simply "the legislature") which typically is either a part of or requires the confidence of (requires the support/approval of) the legislature and is therefore fused to the legislative power instead of being independent. In systems where the legislature is sovereign, the powers of and the organization of the executive are completely dependent on what powers the legislature grants it and the actions of the executive may or may not be subject to judicial review, something which is also controlled by the legislature. The executive may also have legislative or judicial powers in systems where the legislature is sovereign, which is often why the executive is instead referred to as the government since it often possesses non-executive powers.


title: Executive (government)

text: In parliamentary systems, the executive is responsible to the elected legislature, i.e. must maintain the confidence of the legislature (or one part of it, if bicameral). In certain circumstances (varying by state), the legislature can express its lack of confidence in the executive, which causes either a change in governing party or group of parties or a general election. Parliamentary systems have a head of government (who leads the executive, often called ministers) normally distinct from the head of state (who continues through governmental and electoral changes). In the Westminster type of parliamentary system, the principle of separation of powers is not as entrenched as in some others. Members of the executive (ministers), are also members of the legislature, and hence play an important part in both the writing and enforcing of law. In presidential systems, the directly elected head of government appoints the ministers. The ministers can be directly elected by voters.


title: Executive (government)

text: In this context, the executive consists of a leader or leader of an office or multiple offices. Specifically, the top leadership roles of the executive branch may include:


title: Executive (government)

text: In a parliamentary system, a cabinet minister responsible to the legislature is the head of government, while the head of state is usually a largely ceremonial monarch or president.


title: 51st state

text: 51st state in American political discourse refers to areas considered candidates for U.S. statehood, joining the 50 states that have constituted the United States since 1959. The phrase has been applied to external territories as well as parts of existing states which would be admitted as separate states in their own right.


title: 51st state

text: Voters in the District of Columbia and Puerto Rico have both voted for statehood in referendums. As statehood candidates, their admission to the Union requires congressional approval. American Samoa, Guam, the Northern Mariana Islands, and the United States Virgin Islands are also U.S. territories and could potentially become U.S. states.


title: 51st state

text: The phrase can be used in a positive sense, meaning that a region or territory is so aligned, supportive, and conducive with the United States, that it is like a U.S. state, or in a pejorative sense, meaning an area or region is under excessive American cultural or military influence or control. People who believe their local or national culture has become too Americanized sometimes use the term in reference to their own countries. Before Alaska and Hawaii became states of the United States in 1959, the corresponding expression was "the 49th state".


title: 51st state

text: Article IV, Section 3, Clause 1 of the United States Constitution authorizes Congress to admit new states into the United States (beyond the thirteen already in existence at the time the Constitution went into effect in 1788). Historically, most new states brought into being by Congress have been established from an organized incorporated territory, created and governed by Congress. In some cases, an entire territory became a state; in others, some part of a territory became a state. As defined in a 1953 U.S. Senate Committee on Interior and Insular Affairs, the traditionally accepted requirements for statehood are:


title: 51st state

text: In most cases, the organized government of a territory made known the sentiment of its population in favor of statehood, usually by referendum. Congress then directed that government to organize a constitutional convention to write a state constitution. Upon acceptance of that constitution by the people of the territory and then by Congress, a joint resolution would be adopted granting statehood. The President would then issue a proclamation announcing the addition of a new state to the Union. While Congress, which has ultimate authority over the admission of new states, has usually followed this procedure, there have been occasions (because of unique, case-specific circumstances) when it did not.


title: 51st state

text: A simple majority in each House of Congress is required to pass statehood legislation; however, in the United States Senate, the filibuster requires 60 votes to invoke cloture. Some statehood advocacy organizations have called for amending or abolishing the filibuster as a path to achieve statehood. As with other legislation, the President can sign or veto statehood bills that pass, and Congress has the power to override a veto with a two-thirds majority.


title: 51st state

text: If a new U.S. state were to be admitted, it would require a new design of the flag to accommodate an additional star for the 51st state. However, according to the U.S. Army Institute of Heraldry, an existing United States flag never becomes obsolete. In the event that a new state is added to the Union and a 51-star flag is approved, any previously approved American flag (such as the 50-star flag) may continue to be used and displayed until no longer serviceable.


title: 51st state

text: The District of Columbia is often mentioned as a candidate for statehood. In Federalist No. 43 of "The Federalist Papers", James Madison considered the implications of the definition of the "seat of government" found in the United States Constitution. Although he noted potential conflicts of interest, and the need for a "municipal legislature for local purposes", Madison did not address the district's role in national voting. Legal scholars disagree on whether a simple act of Congress can admit the District as a state, due to its status as the seat of government of the United States, which Article I, Section 8 of the Constitution requires to be under the exclusive jurisdiction of Congress; depending on the interpretation of this text, admission of the full District as a state may require a Constitutional amendment, which is much more difficult to enact.


title: 51st state

text: The District of Columbia residents who support the statehood movement sometimes use the slogan "Taxation without representation" to denote their lack of Congressional representation. The phrase is a shortened version of the Revolutionary War protest motto "no taxation without representation" omitting the initial "No", and is now printed on newly issued District of Columbia license plates (although a driver may choose to have the District of Columbia website address instead). President Bill Clinton's presidential limousine had the "Taxation without representation" license plate late in his term, while President George W. Bush had the vehicle's plates changed shortly after beginning his term in office. President Barack Obama had the license plates changed back to the protest style shortly before his second-term inauguration. President Donald Trump eventually removed the license plate and signaled opposition to DC statehood.


title: 51st state

text: This position was carried by the D.C. Statehood Party, a political party; it has since merged with the local Green Party affiliate to form the D.C. Statehood Green Party. The nearest this movement ever came to success was in 1978, when Congress passed the District of Columbia Voting Rights Amendment. Two years later in 1980, local citizens passed an initiative written and filed by J. Edward Guinan calling for a constitutional convention for a new state. In 1982, voters ratified the constitution of the state, which was to be called New Columbia. The drive for statehood stalled in 1985, however, when the District of Columbia Voting Rights Amendment failed because not enough states ratified the amendment within the seven-year span specified.