Cork has been culturally diverse for many years, from Huguenot communities in the 17th century, through to Eastern European communities and a smaller numbers from African and Asian nations in the 20th and 21st centuries. This is reflected in the multi-cultural restaurants and shops, including specialist shops for East-European or Middle-Eastern food, Chinese and Thai restaurants, French patisseries, Indian buffets, and Middle Eastern kebab houses. Cork saw some Jewish immigration from Lithuania and Russia in the late 19th century. Jewish citizens such as Gerald Goldberg (several times Lord Mayor), David Marcus (novelist) and Louis Marcus (documentary maker) played notable roles in 20th century Cork. Today, the Jewish community is relatively small in population, although the city still has a Jewish quarter and synagogue. Cork also features various Christian churches, as well as a mosque. Some Catholic masses around the city are said in Polish, Filipino, Lithuanian, Romanian and other languages, in addition to the traditional Latin and local Irish and English language services.


The Cork accent, part of the Southwest dialect of Hiberno-English, displays various features which set it apart from other accents in Ireland. Patterns of tone and intonation often rise and fall, with the overall tone tending to be more high-pitched than other Irish accents. English spoken in Cork has a number of dialect words that are peculiar to the city and environs. Like standard Hiberno-English, some of these words originate from the Irish language, but others through other languages Cork's inhabitants encountered at home and abroad. The Cork accent displays varying degrees of rhoticity, usually depending on the social-class of the speaker.


The city's FM radio band features RTÉ Radio 1, RTÉ 2fm, RTÉ lyric fm, RTÉ Raidió na Gaeltachta, Today FM, 4fm, Newstalk and the religious station Spirit Radio. There are also local stations such as Cork's 96FM, Cork's Red FM, C103, CUH 102.0FM, UCC 98.3FM (formerly Cork Campus Radio 97.4fm) and Christian radio station Life 93.1FM. Cork also has a temporary licensed city-wide community station 'Cork FM Community Radio' on 100.5FM, which is currently on-air on Saturdays and Sundays only. Cork has also been home to pirate radio stations, including South Coast Radio and ERI in the 1980s. Today some small pirates stations remain. A number of neighbouring counties radio stations can be heard in parts of Cork City including Radio Kerry at 97.0 and WLR FM on 95.1.


Cork is home to one of Ireland's main national newspapers, the Irish Examiner (formerly the Cork Examiner). It also prints the Evening Echo, which for decades has been connected to the Echo Boys, who were poor and often homeless children who sold the newspaper. Today, the shouts of the vendors selling the Echo can still be heard in various parts of the city centre. One of the biggest free newspapers in the city is the Cork Independent. The city's University publishes the UCC Express and Motley magazine.


Cork features architecturally notable buildings originating from the Medieval to Modern periods. The only notable remnant of the Medieval era is the Red Abbey. There are two cathedrals in the city; St. Mary's Cathedral and Saint Fin Barre's Cathedral. St Mary's Cathedral, often referred to as the North Cathedral, is the Catholic cathedral of the city and was begun in 1808. Its distinctive tower was added in the 1860s. St Fin Barre's Cathedral serves the Protestant faith and is possibly the more famous of the two. It is built on the foundations of an earlier cathedral. Work began in 1862 and ended in 1879 under the direction of architect William Burges.


St. Patrick's Street, the main street of the city which was remodelled in the mid-2000s, is known for the architecture of the buildings along its pedestrian-friendly route and is the main shopping thoroughfare. The reason for its curved shape is that it originally was a channel of the River Lee that was built over on arches. The General Post Office, with its limestone façade, is on Oliver Plunkett Street, on the site of the Theatre Royal which was built in 1760 and burned down in 1840. The English circus proprietor Pablo Fanque rebuilt an amphitheatre on the spot in 1850, which was subsequently transformed into a theatre and then into the present General Post Office in 1877.  The Grand Parade is a tree-lined avenue, home to offices, shops and financial institutions. The old financial centre is the South Mall, with several banks whose interior derive from the 19th century, such as the Allied Irish Bank's which was once an exchange.


Many of the city's buildings are in the Georgian style, although there are a number of examples of modern landmark structures, such as County Hall tower, which was, at one time the tallest building in Ireland until being superseded by another Cork City building: The Elysian. Across the river from County Hall is Ireland's longest building; built in Victorian times, Our Lady's Psychiatric Hospital has now been renovated and converted into a residential housing complex called Atkins Hall, after its architect William Atkins.


Other notable places include Elizabeth Fort, the Cork Opera House, Christ Church on South Main Street (now the Triskel Arts Centre and original site of early Hiberno-Norse church), St Mary's Dominican Church on Popes Quay and Fitzgerald's Park to the west of the city, which contains the Cork Public Museum. Other popular tourist attractions include the grounds of University College Cork, through which the River Lee flows, the Women's Gaol at Sundays Well (now a heritage centre) and the English Market. This covered market traces its origins back to 1610, and the present building dates from 1786.


While local government in Ireland has limited powers in comparison with other countries, the council has responsibility for planning, roads, sanitation, libraries, street lighting, parks, and a number of other important functions. Cork City Council has 31 elected members representing six electoral wards. The members are affiliated to the following political parties: Fine Gael (5 members), Fianna Fáil (10 members), Sinn Féin (8 members), Anti-Austerity Alliance (3 members), Workers' Party (1 member), Independents (4 members). Certain councillors are co-opted to represent the city at the South-West Regional Authority. A new Lord Mayor of Cork is chosen in a vote by the elected members of the council under a D'Hondt system count.


The retail trade in Cork city includes a mix of both modern, state of the art shopping centres and family owned local shops. Department stores cater for all budgets, with expensive boutiques for one end of the market and high street stores also available. Shopping centres can be found in many of Cork's suburbs, including Blackpool, Ballincollig, Douglas, Ballyvolane, Wilton and Mahon Point. Others are available in the city centre. These include the recently[when?] completed development of two large malls The Cornmarket Centre on Cornmarket Street, and new the retail street called "Opera Lane" off St. Patrick's Street/Academy Street. The Grand Parade scheme, on the site of the former Capitol Cineplex, was planning-approved for 60,000 square feet (5,600 m2) of retail space, with work commencing in 2016. Cork's main shopping street is St. Patrick's Street and is the most expensive street in the country per sq. metre after Dublin's Grafton Street. As of 2015[update] this area has been impacted by the post-2008 downturn, with many retail spaces available for let.[citation needed] Other shopping areas in the city centre include Oliver Plunkett St. and Grand Parade. Cork is also home to some of the country's leading department stores with the foundations of shops such as Dunnes Stores and the former Roches Stores being laid in the city. Outside the city centre is Mahon Point Shopping Centre.


Cork City is at the heart of industry in the south of Ireland. Its main area of industry is pharmaceuticals, with Pfizer Inc. and Swiss company Novartis being big employers in the region. The most famous product of the Cork pharmaceutical industry is Viagra. Cork is also the European headquarters of Apple Inc. where over 3,000 staff are involved in manufacturing, R&D and customer support. Logitech and EMC Corporation are also important IT employers in the area. Three hospitals are also among the top ten employers in the city (see table below).


The city is also home to the Heineken Brewery that brews Murphy's Irish Stout and the nearby Beamish and Crawford brewery (taken over by Heineken in 2008) which have been in the city for generations. 45% of the world's Tic Tac sweets are manufactured at the city's Ferrero factory. For many years, Cork was the home to Ford Motor Company, which manufactured cars in the docklands area before the plant was closed in 1984. Henry Ford's grandfather was from West Cork, which was one of the main reasons for opening up the manufacturing facility in Cork. But technology has replaced the old manufacturing businesses of the 1970s and 1980s, with people now working in the many I.T. centres of the city – such as Amazon.com, the online retailer, which has set up in Cork Airport Business Park.


Public bus services within the city are provided by the national bus operator Bus Éireann. City routes are numbered from 201 through to 219 and connect the city centre to the principal suburbs, colleges, shopping centres and places of interest. Two of these bus routes provide orbital services across the Northern and Southern districts of the city respectively. Buses to the outer suburbs, such as Ballincollig, Glanmire, Midleton and Carrigaline are provided from the city's bus terminal at Parnell Place in the city centre. Suburban services also include shuttles to Cork Airport, and a park and ride facility in the south suburbs only.


The Cork area has seen improvements in road infrastructure in recent years. For example, the Cork South Link dual carriageway was built in the early 1980s, to link the Kinsale Road roundabout with the city centre. Shortly afterwards, the first sections of the South Ring dual carriageway were opened. Work continued through the 1990s on extending the N25 South Ring Road, with the opening of the Jack Lynch Tunnel under the River Lee being a significant addition. The Kinsale Road flyover opened in August 2006 to remove a bottleneck for traffic heading to Cork Airport or Killarney. Other projects completed at this time include the N20 Blackpool bypass and the N20 Cork to Mallow road projects. The N22 Ballincollig dual carriageway bypass, which links to the Western end of the Cork Southern Ring road was opened in September 2004. City Centre road improvements include the Patrick Street project - which reconstructed the street with a pedestrian focus. The M8 motorway links Cork with Dublin.


Cork was one of the most rail-oriented cities in Ireland, featuring eight stations at various times. The main route, still much the same today, is from Dublin Heuston. Originally terminating on the city's outskirts at Blackpool, the route now reaches the city centre terminus of Kent Station via Glanmire tunnel. Now a through station, the line through Kent connects the towns of Cobh and Midleton east of the city. This also connected to the seaside town of Youghal, until the 1980s.[citation needed]


Within the city there have been two tram networks in operation. A proposal to develop a horse-drawn tram (linking the city's railway termini) was made by American George Francis Train in the 1860s, and implemented in 1872 by the Cork Tramway Company. However, the company ceased trading in 1875 after Cork Corporation refused permission to extend the line, mainly because of objections from cab operators to the type of tracks which – although they were laid to the Irish national railway gauge of 5 ft 3in – protruded from the road surface.[citation needed]


The Cork Suburban Rail system also departs from Kent Station and provides connections to parts of Metropolitan Cork. Stations include Little Island, Mallow, Midleton, Fota and Cobh. In July 2009 the Glounthaune to Midleton line was reopened, with new stations at Carrigtwohill and Midleton (with future stations planned for Kilbarry, Monard, Carrigtwohill West and Blarney). Little Island Railway Station serves Cork's Eastern Suburbs, while Kilbarry Railway Station is planned to serve the Northern Suburbs.


The National Maritime College of Ireland is also located in Cork and is the only college in Ireland in which Nautical Studies and Marine Engineering can be undertaken. CIT also incorporates the Cork School of Music and Crawford College of Art and Design as constituent schools. The Cork College of Commerce is the largest post-Leaving Certificate college in Ireland and is also the biggest provider of Vocational Preparation and Training courses in the country.[citation needed] Other 3rd level institutions include Griffith College Cork, a private institution, and various other colleges.


Research institutes linked to the third level colleges in the city support the research and innovation capacity of the city and region. Examples include the Tyndall National Institute (ICT hardware research), IMERC (Marine Energy), Environmental Research Institute, NIMBUS (Network Embedded Systems); and CREATE (Advanced Therapeutic Engineering). UCC and CIT also have start-up company incubation centres. In UCC, the IGNITE Graduate Business Innovation Centre aims to foster and support entrepreneurship. In CIT, The Rubicon Centre is a business innovation hub that is home to 57 knowledge based start-up companies.


Hurling and football are the most popular spectator sports in the city. Hurling has a strong identity with city and county – with Cork winning 30 All-Ireland Championships. Gaelic football is also popular, and Cork has won 7 All-Ireland Senior Football Championship titles. There are many Gaelic Athletic Association clubs in Cork City, including Blackrock National Hurling Club, St. Finbarr's, Glen Rovers, Na Piarsaigh and Nemo Rangers. The main public venues are Páirc Uí Chaoimh and Páirc Uí Rinn (named after the noted Glen Rovers player Christy Ring). Camogie (hurling for ladies) and women's gaelic football are increasing in popularity.


There are a variety of watersports in Cork, including rowing and sailing. There are five rowing clubs training on the river Lee, including Shandon BC, UCC RC, Pres RC, Lee RC, and Cork BC. Naomhóga Chorcaí is a rowing club whose members row traditional naomhóga on the Lee in occasional competitions. The "Ocean to City" race has been held annually since 2005, and attracts teams and boats from local and visiting clubs who row the 24 kilometres (15 mi) from Crosshaven into Cork city centre. The decision to move the National Rowing Center to Inniscarra has boosted numbers involved in the sport.[citation needed] Cork's maritime sailing heritage is maintained through its sailing clubs. The Royal Cork Yacht Club located in Crosshaven (outside the city) is the world's oldest yacht club, and "Cork Week" is a notable sailing event.


The most notable cricket club in Cork is Cork County Cricket Club, which was formed in 1874. Although located within the Munster jurisdiction, the club plays in the Leinster Senior League. The club plays at the Mardyke, a ground which has hosted three first-class matches in 1947, 1961 and 1973. All three involved Ireland playing Scotland. The Cork Cricket Academy operates within the city, with the stated aim of introducing the sport to schools in the city and county. Cork's other main cricket club, Harlequins Cricket Club, play close to Cork Airport.


The city is also the home of road bowling, which is played in the north-side and south-west suburbs. There are also boxing and martial arts clubs (including Brazilian jiu-jitsu, Karate, Muay Thai and Taekwondo) within the city. Cork Racing, a motorsport team based in Cork, has raced in the Irish Formula Ford Championship since 2005. Cork also hosts one of Ireland's most successful Australian Rules Football teams, the Leeside Lions, who have won the Australian Rules Football League of Ireland Premiership four times (in 2002, 2003, 2005 and 2007). There are also inline roller sports, such as hockey and figure skating, which transfer to the ice over the winter season.[citation needed]


Galicia (English i/ɡəˈlɪsiə/, /ɡəˈlɪʃə/; Galician: [ɡaˈliθja] ( listen), [ħaˈliθja], or [ħaˈlisja]; Spanish: [ɡaˈliθja]; Galician and Portuguese: Galiza, [ɡaˈliθa] ( listen), [ħaˈliθa] or [ħaˈlisa]) is an autonomous community of Spain and historic nationality under Spanish law. Located in the North-West of the Iberian Peninsula, it comprises the provinces of A Coruña, Lugo, Ourense and Pontevedra, being bordered by Portugal to the south, the Spanish autonomous communities of Castile and León and Asturias to the east, and the Atlantic Ocean to the west and the north. It had a population of 2,765,940 in 2013 and has a total area of 29,574 km2 (11,419 sq mi). Galicia has over 1,660 km (1,030 mi) of coastline, including its offshore islands and islets, among them Cíes Islands, Ons, Sálvora, Cortegada, and—the largest and most populated—A Illa de Arousa.


The area now called Galicia was first inhabited by humans during the Middle Paleolithic period, and it takes its name from the Gallaeci, the Celtic peoples living north of the Douro river during the last millennium BC, in a region largely coincidental with that of the Iron Age local Castro culture. Galicia was incorporated into the Roman Empire at the end of the Cantabrian Wars in 19 BC, being turned into a Roman province in the 3rd century AD. In 410, the Germanic Suebi established a kingdom with its capital in Braga (Portugal) which was incorporated into that of the Visigoths in 585. In 711, the Arabs invaded the Iberian Peninsula, taking the Visigoth kingdom, but soon in 740 Galicia was incorporated into the Christian kingdom of Asturias. During the Middle Ages, the kingdom of Galicia was occasionally ruled by its own kings, but most of the time it was leagued to the kingdom of Leon and later to that of Castile, while maintaining its own legal and customary practices and personality. From the 13th century on, the kings of Castile, as kings of Galicia, appointed an Adiantado-mór, whose attributions passed to the Governor and Captain General of the Kingdom of Galiza from the last years of the 15th century. The Governor also presided the Real Audiencia do Reino de Galicia, a royal tribunal and government body. From the 16th century, the representation and voice of the kingdom was held by an assembly of deputies and representatives of the cities of the kingdom, the Cortes or Junta of the Kingdom of Galicia, an institution which was forcibly discontinued in 1833 when the kingdom was divided into four administrative provinces with no legal mutual links. During the 19th and 20th centuries, demand grew for self-government and for the recognition of the personality of Galicia, a demand which led to the frustrated Statute of Autonomy of 1936, and to the Statute of Autonomy of 1981, currently in force.


The interior of Galicia is characterized by its hilly landscape, although mountain ranges rise to 2,000 m (6,600 ft) in the east and south. The coastal areas are mostly an alternate series of rías (submerged valleys where the sea penetrates tens of kilometres inland) and cliffs. The climate of Galicia is temperate and rainy, but it is also markedly drier in the summer, being usually classified as Oceanic in the west and north, and Mediterranean in the southeast. Its topographic and climatic conditions have made animal husbandry and farming the primary source of Galicia's wealth for most of its history. With the exception of shipbuilding and food processing, Galicia was largely a semi-subsistence farming and fishing economy and did not experience significant industrialization until after the mid-20th century. In 2012, the gross domestic product at purchasing power parity was €56,000 million, with a nominal GDP per capita of €20,700. The population is largely concentrated in two coastal areas: from Ferrol to A Coruña in the northwest and from Pontevedra to Vigo in the southwest. To a lesser extent, there are smaller populations around the interior cities of Lugo, Ourense and Santiago de Compostela. The political capital is Santiago de Compostela, in the province of A Coruña. Vigo, in the province of Pontevedra, is the most populous municipality with 294,997 (2014), while A Coruña is the most populous city with 215.227 (2014).


The name evolved during the Middle Ages from Gallaecia, sometimes written Galletia, to Gallicia. In the 13th century, with the written emergence of the Galician language, Galiza became the most usual written form of the name of the country, being replaced during the 15th and 16th centuries by the current form, Galicia, which coincides with the Castilian Spanish name. The historical denomination Galiza became popular again during the end of the 19th and the first three-quarters of the 20th century, being still used with some frequency today, although not by the Xunta de Galicia, the local devolved government. The Royal Galician Academy, the institution responsible for regulating the Galician language, whilst recognizing it as a legitimate current denomination, has stated that the only official name of the country is Galicia.


Although the etymology of the name has been studied since the 7th century by authors like Isidore of Seville —who wrote that "Galicians are called so, because of their fair skin, as the Gauls", relating the name to the Greek word for milk—, currently scholars derive the name of the ancient Callaeci either from Proto-Indo-European *kal-n-eH2 'hill', through a local relational suffix -aik-, so meaning 'the hill (people)'; or either from Proto-Celtic *kallī- 'forest', so meaning 'the forest (people)'. In any case, Galicia, being per se a derivation of the ethnic name Kallaikói, would mean 'the land of the Galicians'.


The oldest attestation of human presence in Galicia has been found in the Eirós Cave, in the municipality of Triacastela, which has preserved animal remains and Neanderthal stone objects from the Middle Paleolithic. The earliest culture to have left significant architectural traces is the Megalithic culture which expanded along the western European coasts during the Neolithic and Calcolithic eras. Thousands of Megalithic tumuli are distributed throughout the country, but mostly along the coastal areas. Within each tumulus is a stone burial chamber known locally as anta (dolmen), frequently preceded by a corridor. Galicia was later fully affected by the Bell Beaker culture. While its rich mineral deposits - tin and gold - led to the development of Bronze Age metallurgy, and to the commerce of bronze and gold items all along the Atlantic façade of Western Europe, where a common elite's culture evolved during the Atlantic Bronze Age.


The Castro culture ('Culture of the Castles') developed during the Iron Age, and flourished during the second half of the first millennium BC. It is usually considered a local evolution of the Atlantic Bronze Age, with later developments and influences and overlapping into the Roman era. Geographically, it corresponds to the people Roman called Gallaeci, which were composed by a large series of nations or tribes, among them the Artabri, Bracari, Limici, Celtici, Albiones and Lemavi. They were capable fighters: Strabo described them as the most difficult foes the Romans encountered in conquering Lusitania, while Appian mentions their warlike spirit, noting that the women bore their weapons side by side with their men, frequently preferring death to captivity. According to Pomponius Mela all the inhabitants of the coastal areas were Celtic people.


Gallaeci lived in castros. These were usually annular forts, with one or more concentric earthen or stony walls, with a trench in front of each one. They were frequently located at hills, or in seashore cliffs and peninsulas. Some well known castros can be found, in the seashore, at Fazouro, Santa Tegra, Baroña and O Neixón, and inland at San Cibrao de Lás, Borneiro, Castromao, and Viladonga. Some other distinctive features, such as temples, baths, reservoirs, warrior statues and decorative carvings have been found associated to this culture, together with rich gold and metalworking traditions.


Later the Muslims invaded Spain (711), but the Arabs and Moors never managed to have any real control over Galicia, which was later incorporated into the expanding Christian Kingdom of Asturias, usually known as Gallaecia or Galicia (Yillīqiya and Galīsiya) by Muslim Chroniclers, as well as by many European contemporaries. This era consolidated Galicia as a Christian society which spoke a Romance language. During the next century Galician noblemen took northern Portugal, conquering Coimbra in 871, thus freeing what were considered the southernmost city of ancient Galicia.


The Roman legions first entered the area under Decimus Junius Brutus in 137–136 BC, but the country was only incorporated into the Roman Empire by the time of Augustus (29 BC – 19 BC). The Romans were interested in Galicia mainly for its mineral resources, most notably gold. Under Roman rule, most Galician hillforts began to be – sometimes forcibly – abandoned, and Gallaeci served frequently in the Roman army as auxiliary troops. Romans brought new technologies, new travel routes, new forms of organizing property, and a new language; latin. The Roman Empire established its control over Galicia through camps (castra) as Aquis Querquennis, Ciadella camp or Lucus Augusti (Lugo), roads (viae) and monuments as the lighthouse known as Tower of Hercules, in Corunna, but the remoteness and lesser interest of the country since the 2nd century of our era, when the gold mines stopped being productive, led to a lesser degree of Romanization. In the 3rd century it was made a province, under the name Gallaecia, which included also northern Portugal, Asturias, and a large section of what today is known as Castile and León.


In the early 5th century, the deep crisis suffered by the Roman Empire allowed different tribes of Central Europe (Suebi, Vandals and Alani) to cross the Rhine and penetrate into the rule on 31 December 406. Its progress towards the Iberian Peninsula forced the Roman authorities to establish a treaty (foedus) by which the Suebi would settle peacefully and govern Galicia as imperial allies. So, from 409 Galicia was taken by the Suebi, forming the first medieval kingdom to be created in Europe, in 411, even before the fall of the Roman Empire, being also the first Germanic kingdom to mint coinage in Roman lands. During this period a Briton colony and bishopric (see Mailoc) was established in Northern Galicia (Britonia), probably as foederati and allies of the Suebi. In 585, the Visigothic King Leovigild invaded the Suebic kingdom of Galicia and defeated it, bringing it under Visigoth control.


In the 9th century, the rise of the cult of the Apostle James in Santiago de Compostela gave Galicia a particular symbolic importance among Christians, an importance it would hold throughout the Reconquista. As the Middle Ages went on, Santiago became a major pilgrim destination and the Way of Saint James (Camiño de Santiago) a major pilgrim road, a route for the propagation of Romanesque art and the words and music of the troubadors. During the 10th and 11th centuries, a period during which Galician nobility become related to the royal family, Galicia was at times headed by its own native kings, while Vikings (locally known as Leodemanes or Lordomanes) occasionally raided the coasts. The Towers of Catoira (Pontevedra) were built as a system of fortifications to prevent and stop the Viking raids on Santiago de Compostela.


In 1063, Ferdinand I of Castile divided his realm among his sons, and the Kingdom of Galicia was granted to Garcia II of Galicia. In 1072, it was forcibly annexed by Garcia's brother Alfonso VI of León; from that time Galicia was united with the Kingdom of León under the same monarchs. In the 13th century Alfonso X of Castile standardized the Castilian language and made it the language of court and government. Nevertheless, in his Kingdom of Galicia the Galician language was the only language spoken, and the most used in government and legal uses, as well as in literature.


On the other hand, the lack of an effective royal justice system in the Kingdom led to the social conflict known as the Guerras Irmandiñas ('Wars of the brotherhoods'), when leagues of peasants and burghers, with the support of a number of knights, noblemen, and under legal protection offered by the remote king, toppled many of the castles of the Kingdom and briefly drove the noblemen into Portugal and Castile. Soon after, in the late 15th century, in the dynastic conflict between Isabella I of Castile and Joanna La Beltraneja, part of the Galician aristocracy supported Joanna. After Isabella's victory, she initiated an administrative and political reform which the chronicler Jeronimo Zurita defined as "doma del Reino de Galicia": 'It was then when the taming of Galicia began, because not just the local lords and knights, but all the people of that nation were the ones against the others very bold and warlike'. These reforms, while establishing a local government and tribunal (the Real Audiencia del Reino de Galicia) and bringing the nobleman under submission, also brought most Galician monasteries and institutions under Castilian control, in what has been criticized as a process of centralisation. At the same time the kings began to call the Xunta or Cortes of the Kingdom of Galicia, an assembly of deputies or representatives of the cities of the Kingdom, to ask for monetary and military contributions. This assembly soon developed into the voice and legal representation of the Kingdom, and the depositary of its will and laws.


The modern period of the kingdom of Galicia began with the murder or defeat of some of the most powerful Galician lords, such as Pedro Álvarez de Sotomayor, called Pedro Madruga, and Rodrigo Henriquez Osorio, at the hands of the Castilian armies sent to Galicia between the years 1480 and 1486. Isabella I of Castile, considered a usurper by many Galician nobles, eradicated all armed resistance and definitively established the royal power of the Castilian monarchy. Fearing a general revolt, the monarchs ordered the banishing of the rest of the great lords like Pedro de Bolaño, Diego de Andrade or Lope Sánchez de Moscoso, among others.


The establishment of the Santa Hermandad in 1480, and of the Real Audiencia del Reino de Galicia in 1500—a tribunal and executive body directed by the Governor-Captain General as a direct representative of the King—implied initially the submission of the Kingdom to the Crown, after a century of unrest and fiscal insubordination. As a result, from 1480 to 1520 the Kingdom of Galicia contributed more than 10% of the total earnings of the Crown of Castille, including the Americas, well over its economic relevance. Like the rest of Spain, the 16th century was marked by population growth up to 1580, when the simultaneous wars with the Netherlands, France and England hampered Galicia's Atlantic commerce, which consisted mostly in the exportation of sardines, wood, and some cattle and wine.


From that moment Galicia, which participated to a minor extent in the American expansion of the Spanish Empire, found itself at the center of the Atlantic wars fought by Spain against the French and the Protestant powers of England and the Netherlands, whose privateers attacked the coastal areas, but major assaults were not common as the coastline was difficult and the harbors easily defended. The most famous assaults were upon the city of Vigo by Sir Francis Drake in 1585 and 1589, and the siege of A Coruña in 1589 by the English Armada. Galicia also suffered occasional slave raids by Barbary pirates, but not as frequently as the Mediterranean coastal areas. The most famous Barbary attack was the bloody sack of the town of Cangas in 1617. At the time, the king's petitions for money and troops became more frequent, due to the human and economic exhaustion of Castile; the Junta of the Kingdom of Galicia (the local Cortes or representative assembly) was initially receptive to these petitions, raising large sums, accepting the conscription of the men of the kingdom, and even commissioning a new naval squadron which was sustained with the incomes of the Kingdom.


After the rupture of the wars with Portugal and Catalonia, the Junta changed its attitude, this time due to the exhaustion of Galicia, now involved not just in naval or oversea operations, but also in an exhausting war with the Portuguese, war which produced thousands of casualties and refugees and was heavily disturbing to the local economy and commerce. So, in the second half of the 17th century the Junta frequently denied or considerably reduced the initial petitions of the monarch, and though the tension didn't rise to the levels experienced in Portugal or Catalonia, there were frequent urban mutinies and some voices even asked for the secession of the Kingdom of Galicia.


In the early 20th century came another turn toward nationalist politics with Solidaridad Gallega (1907–1912) modeled on Solidaritat Catalana in Catalonia. Solidaridad Gallega failed, but in 1916 Irmandades da Fala (Brotherhood of the Language) developed first as a cultural association but soon as a full-blown nationalist movement. Vicente Risco and Ramón Otero Pedrayo were outstanding cultural figures of this movement, and the magazine Nós ('Us'), founded 1920, its most notable cultural institution, Lois Peña Novo the outstanding political figure.


Galicia was spared the worst of the fighting in that war: it was one of the areas where the initial coup attempt at the outset of the war was successful, and it remained in Nationalist (Franco's army's) hands throughout the war. While there were no pitched battles, there was repression and death: all political parties were abolished, as were all labor unions and Galician nationalist organizations as the Seminario de Estudos Galegos. Galicia's statute of autonomy was annulled (as were those of Catalonia and the Basque provinces once those were conquered). According to Carlos Fernández Santander, at least 4,200 people were killed either extrajudicially or after summary trials, among them republicans, communists, Galician nationalists, socialists and anarchists. Victims included the civil governors of all four Galician provinces; Juana Capdevielle, the wife of the governor of A Coruña; mayors such as Ánxel Casal of Santiago de Compostela, of the Partido Galeguista; prominent socialists such as Jaime Quintanilla in Ferrol and Emilio Martínez Garrido in Vigo; Popular Front deputies Antonio Bilbatúa, José Miñones, Díaz Villamil, Ignacio Seoane, and former deputy Heraclio Botana); soldiers who had not joined the rebellion, such as Generals Rogelio Caridad Pita and Enrique Salcedo Molinuevo and Admiral Antonio Azarola; and the founders of the PG, Alexandre Bóveda and Víctor Casas, as well as other professionals akin to republicans and nationalists, as the journalist Manuel Lustres Rivas or physician Luis Poza Pastrana. Many others were forced to escape into exile, or were victims of other reprisals and removed from their jobs and positions.


General Francisco Franco — himself a Galician from Ferrol — ruled as dictator from the civil war until his death in 1975. Franco's centralizing regime suppressed any official use of the Galician language, including the use of Galician names for newborns, although its everyday oral use was not forbidden. Among the attempts at resistance were small leftist guerrilla groups such as those led by José Castro Veiga ("El Piloto") and Benigno Andrade ("Foucellas"), both of whom were ultimately captured and executed. In the 1960s, ministers such as Manuel Fraga Iribarne introduced some reforms allowing technocrats affiliated with Opus Dei to modernize administration in a way that facilitated capitalist economic development. However, for decades Galicia was largely confined to the role of a supplier of raw materials and energy to the rest of Spain, causing environmental havoc and leading to a wave of migration to Venezuela and to various parts of Europe. Fenosa, the monopolistic supplier of electricity, built hydroelectric dams, flooding many Galician river valleys.


As part of the transition to democracy upon the death of Franco in 1975, Galicia regained its status as an autonomous region within Spain with the Statute of Autonomy of 1981, which begins, "Galicia, historical nationality, is constituted as an Autonomous Community to access to its self-government, in agreement with the Spanish Constitution and with the present Statute (...)". Varying degrees of nationalist or independentist sentiment are evident at the political level. The Bloque Nacionalista Galego or BNG, is a conglomerate of left-wing parties and individuals that claims Galician political status as a nation.


From 1990 to 2005, Manuel Fraga, former minister and ambassador in the Franco dictature, presided over the Galician autonomous government, the Xunta de Galicia. Fraga was associated with the Partido Popular ('People's Party', Spain's main national conservative party) since its founding. In 2002, when the oil tanker Prestige sank and covered the Galician coast in oil, Fraga was accused by the grassroots movement Nunca Mais ("Never again") of having been unwilling to react. In the 2005 Galician elections, the 'People's Party' lost its absolute majority, though remaining (barely) the largest party in the parliament, with 43% of the total votes. As a result, power passed to a coalition of the Partido dos Socialistas de Galicia (PSdeG) ('Galician Socialists' Party'), a federal sister-party of Spain's main social-democratic party, the Partido Socialista Obrero Español (PSOE, 'Spanish Socialist Workers Party') and the nationalist Bloque Nacionalista Galego (BNG). As the senior partner in the new coalition, the PSdeG nominated its leader, Emilio Perez Touriño, to serve as Galicia's new president, with Anxo Quintana, the leader of BNG, as its vice president.


Galicia has a surface area of 29,574 square kilometres (11,419 sq mi). Its northernmost point, at 43°47′N, is Estaca de Bares (also the northernmost point of Spain); its southernmost, at 41°49′N, is on the Portuguese border in the Baixa Limia-Serra do Xurés Natural Park. The easternmost longitude is at 6°42′W on the border between the province of Ourense and the Castilian-Leonese province of Zamora) its westernmost at 9°18′W, reached in two places: the A Nave Cape in Fisterra (also known as Finisterre), and Cape Touriñán, both in the province of A Coruña.


Topographically, a remarkable feature of Galicia is the presence of many firth-like inlets along the coast, estuaries that were drowned with rising sea levels after the ice age. These are called rías and are divided into the smaller Rías Altas ("High Rías"), and the larger Rías Baixas ("Low Rías"). The Rías Altas include Ribadeo, Foz, Viveiro, Barqueiro, Ortigueira, Cedeira, Ferrol, Betanzos, A Coruña, Corme e Laxe and Camariñas. The Rías Baixas, found south of Fisterra, include Corcubión, Muros e Noia, Arousa, Pontevedra and Vigo. The Rías Altas can sometimes refer only to those east of Estaca de Bares, with the others being called Rías Medias ("Intermediate Rías").


All along the Galician coast are various archipelagos near the mouths of the rías. These archipelagos provide protected deepwater harbors and also provide habitat for seagoing birds. A 2007 inventory estimates that the Galician coast has 316 archipelagos, islets, and freestanding rocks. Among the most important of these are the archipelagos of Cíes, Ons, and Sálvora. Together with Cortegada Island, these make up the Atlantic Islands of Galicia National Park. Other significant islands are Islas Malveiras, Islas Sisargas, and, the largest and holding the largest population, Arousa Island.


Galicia is quite mountainous, a fact which has contributed to isolate the rural areas, hampering communications, most notably in the inland. The main mountain range is the Macizo Galaico (Serra do Eixe, Serra da Lastra, Serra do Courel), also known as Macizo Galaico-Leonés, located in the eastern parts, bordering with Castile and León. Noteworthy mountain ranges are O Xistral (northern Lugo), the Serra dos Ancares (on the border with León and Asturias), O Courel (on the border with León), O Eixe (the border between Ourense and Zamora), Serra de Queixa (in the center of Ourense province), O Faro (the border between Lugo and Pontevedra), Cova da Serpe (border of Lugo and A Coruña), Montemaior (A Coruña), Montes do Testeiro, Serra do Suído, and Faro de Avión (between Pontevedra and Ourense); and, to the south, A Peneda, O Xurés and O Larouco, all on the border of Ourense and Portugal.


Galicia is poetically known as the "country of the thousand rivers" ("o país dos mil ríos"). The largest and most important of these rivers is the Minho, known as O Pai Miño (Father Minho), 307.5 km (191.1 mi) long and discharging 419 m3 (548 cu yd) per second, with its affluent the Sil, which has created a spectacular canyon. Most of the rivers in the inland are tributaries of this fluvial system, which drains some 17,027 km2 (6,574 sq mi). Other rivers run directly into the Atlantic Ocean as Lérez or the Cantabrian Sea, most of them having short courses. Only the Navia, Ulla, Tambre, and Limia have courses longer than 100 km (62 mi).


Deforestation and forest fires are a problem in many areas, as is the continual spread of the eucalyptus tree, a species imported from Australia, actively promoted by the paper industry since the mid-20th century. Galicia is one of the more forested areas of Spain, but the majority of Galicia's plantations, usually growing eucalyptus or pine, lack any formal management. Massive eucalyptus, especially Eucalyptus globulus plantation, began in the Francisco Franco era, largely on behalf of the paper company Empresa Nacional de Celulosas de España (ENCE) in Pontevedra, which wanted it for its pulp. Wood products figure significantly in Galicia's economy. Apart from tree plantations Galicia is also notable for the extensive surface occupied by meadows used for animal husbandry, especially cattle , an important activity. Hydroelectric development in most rivers has been a serious concern for local conservationists during the last decades.


The animals most often thought of as being "typical" of Galicia are the livestock raised there. The Galician horse is native to the region, as is the Galician Blond cow and the domestic fowl known as the galiña de Mos. The latter is an endangered species, although it is showing signs of a comeback since 2001. Galicia's woodlands and mountains are home to rabbits, hares, wild boars, and roe deer, all of which are popular with hunters. Several important bird migration routes pass through Galicia, and some of the community's relatively few environmentally protected areas are Special Protection Areas (such as on the Ría de Ribadeo) for these birds. From a domestic point of view, Galicia has been credited for author Manuel Rivas as the "land of one million cows". Galician Blond and Holstein cattle coexist on meadows and farms.


Being located on the Atlantic coastline, Galicia has a very mild climate for the latitude and the marine influence affects most of the province to various degrees. In comparison to similar latitudes on the other side of the Atlantic, winters are exceptionally mild, with consistently heavy rainfall. Snow is rare due to temperatures rarely dropping below freezing. The warmest coastal station of Pontevedra has a yearly mean temperature of 14.8 °C (58.6 °F). Ourense located somewhat inland is only slightly warmer with 14.9 °C (58.8 °F). Due to its exposed north-westerly location, the climate is still very cool by Spanish standards. In coastal areas summers are temperered, averaging around 25 °C (77 °F) in Vigo. Temperatures are further cooler in A Coruña, with a subdued 22.8 °C (73.0 °F) normal. Temperatures do however soar in inland areas such as Ourense, where days above 30 °C (86 °F) are very regular.


The lands of Galicia are ascribed to two different areas in the Köppen climate classification: a south area (roughly, the province of Ourense and Pontevedra) with tendencies to have some summer drought, classified as a warm-summer Mediterranean climate (Csb), with mild temperatures and rainfall usual throughout the year; and the western and northern coastal regions, the provinces of Lugo and A Coruña, which are characterized by their Oceanic climate (Cfb), with a more uniform precipitation distribution along the year, and milder summers. However, precipitation in southern coastal areas are often classified as oceanic since the averages remain significantly higher than a typical mediterranean climate.


As an example, Santiago de Compostela, the political capital city, has an average of 129 rainy days and 1,362 millimetres (53.6 in) per year (with just 17 rainy days in the three summer months) and 2,101 sunlight hours per year, with just 6 days with frosts per year. But the colder city of Lugo, to the east, has an average of 1,759 sunlight hours per year, 117 days with precipitations (> 1 mm) totalling 901.54 millimetres (35.5 in), and 40 days with frosts per year. The more mountainous parts of the provinces of Ourense and Lugo receive significant snowfall during the winter months. The sunniest city is Pontevedra with 2,223 sunny hours per year.


Galicia is further divided into 53 comarcas, 315 municipalities (93 in A Coruña, 67 in Lugo, 92 in Ourense, 62 in Pontevedra) and 3,778 parishes. Municipalities are divided into parishes, which may be further divided into aldeas ("hamlets") or lugares ("places"). This traditional breakdown into such small areas is unusual when compared to the rest of Spain. Roughly half of the named population entities of Spain are in Galicia, which occupies only 5.8 percent of the country's area. It is estimated that Galicia has over a million named places, over 40,000 of them being communities.


In comparison to the other regions of Spain, the major economic benefit of Galicia is its fishing Industry. Galicia is a land of economic contrast. While the western coast, with its major population centers and its fishing and manufacturing industries, is prosperous and increasing in population, the rural hinterland — the provinces of Ourense and Lugo — is economically dependent on traditional agriculture, based on small landholdings called minifundios. However, the rise of tourism, sustainable forestry and organic and traditional agriculture are bringing other possibilities to the Galician economy without compromising the preservation of the natural resources and the local culture.


Galicia was late to catch the tourism boom that has swept Spain in recent decades, but the coastal regions (especially the Rías Baixas and Santiago de Compostela) are now significant tourist destinations and are especially popular with visitors from other regions in Spain, where the majority of tourists come from. In 2007, 5.7 million tourists visited Galicia, an 8% growth over the previous year, and part of a continual pattern of growth in this sector. 85% of tourists who visit Galicia visit Santiago de Compostela. Tourism constitutes 12% of Galician GDP and employs about 12% of the regional workforce.


The most important Galician fishing port is the Port of Vigo; It is one of the world's leading fishing ports, second only to Tokyo, with an annual catch worth 1,500 million euros. In 2007 the port took in 732,951 metric tons (721,375 long tons; 807,940 short tons) of fish and seafood, and about 4,000,000 metric tons (3,900,000 long tons; 4,400,000 short tons) of other cargoes. Other important ports are Ferrol, A Coruña, and the smaller ports of Marín and Vilagarcía de Arousa, as well as important recreational ports in Pontevedra and Burela. Beyond these, Galicia has 120 other organized ports.


Within Galicia are the Autopista AP-9 from Ferrol to Vigo and the Autopista AP-53 (also known as AG-53, because it was initially built by the Xunta de Galicia) from Santiago to Ourense. Additional roads under construction include Autovía A-54 from Santiago de Compostela to Lugo, and Autovía A-56 from Lugo to Ourense. The Xunta de Galicia has built roads connecting comarcal capitals, such as the aforementioned AG-53, Autovía AG-55 connecting A Coruña to Carballo or AG-41 connecting Pontevedra to Sanxenxo.


The first railway line in Galicia was inaugurated 15 September 1873. It ran from O Carril, Vilagarcía de Arousa to Cornes, Conxo, Santiago de Compostela. A second line was inaugurated in 1875, connecting A Coruña and Lugo. In 1883, Galicia was first connected by rail to the rest of Spain, by way of O Barco de Valdeorras. Galicia today has roughly 1,100 kilometres (680 mi) of rail lines. Several 1,668 mm (5 ft 5 21⁄32 in) Iberian gauge lines operated by Adif and Renfe Operadora connect all the important Galician cities. A 1,000 mm (3 ft 3 3⁄8 in) metre gauge line operated by FEVE connects Ferrol to Ribadeo and Oviedo. The only electrified line is the Ponferrada-Monforte de Lemos-Ourense-Vigo line. Several high-speed rail lines are under construction. Among these are the Olmedo-Zamora-Galicia high-speed rail line that opened partly in 2011, and the AVE Atlantic Axis route, which will connect all of the major Galician Atlantic coast cities A Coruña, Santiago de Compostela, Pontevedra and Vigo to Portugal. Another projected AVE line will connect Ourense to Pontevedra and Vigo.


The rapid increase of population of A Coruña, Vigo and to a lesser degree other major Galician cities, like Ourense, Pontevedra or Santiago de Compostela during the years that followed the Spanish Civil War during the mid-20th century occurred as the rural population declined: many villages and hamlets of the four provinces of Galicia disappeared or nearly disappeared during the same period. Economic development and mechanization of agriculture resulted in the fields being abandoned, and most of the population has moving to find jobs in the main cities. The number of people working in the Tertiary and Quaternary sectors of the economy has increased significantly.


Spanish was nonetheless the only official language in Galicia for more than four centuries. Over the many centuries of Castilian domination, Galician faded from day-to-day use in urban areas. The period since the re-establishment of democracy in Spain—in particular since the Lei de Normalización Lingüística ("Law of Linguistic Normalization", Ley 3/1983, 15 June 1983)—represents the first time since the introduction of mass education that a generation has attended school in Galician (Spanish is also still taught in Galician schools).


Nowadays, Galician is resurgent, though in the cities it remains a "second language" for most. According to a 2001 census, 99.16 percent of the populace of Galicia understand the language, 91.04 percent speak it, 68.65 percent read it and 57.64 percent write it. The first two numbers (understanding and speaking) remain roughly the same as a decade earlier; the latter two (reading and writing) both show enormous gains: a decade earlier, only 49.3 percent of the population could read Galician, and only 34.85 percent could write it. This fact can be easily explained because of the impossibility of teaching Galician during the Francisco Franco era, so older people speak the language but have no written competence. Galician is the highest-percentage spoken language in its region among the regional languages of Spain.


The earliest known document in Galician-Portuguese dates from 1228. The Foro do bo burgo do Castro Caldelas was granted by Alfonso IX of León to the town of Burgo, in Castro Caldelas, after the model of the constitutions of the town of Allariz. A distinct Galician Literature emerged during the Middle Ages: In the 13th century important contributions were made to the romance canon in Galician-Portuguese, the most notable those by the troubadour Martín Codax, the priest Airas Nunes, King Denis of Portugal and King Alfonso X of Castile, Alfonso O Sabio ("Alfonso the Wise"), the same monarch who began the process of establishing the hegemony of Castilian. During this period, Galician-Portuguese was considered the language of love poetry in the Iberian Romance linguistic culture. The names and memories of Codax and other popular cultural figures are well preserved in modern Galicia and, despite the long period of Castilian linguistic domination, these names are again household words.


Christianity is the most widely practised religion in Galicia, as it has been since its introduction in Late Antiquity, although it lived alongside the old Gallaeci religion for a few centuries. Today about 73% of Galicians identify themselves as Christians. The largest form of Christianity practised in the present day is Catholicism, though only 20% of the population described themselves as active members. The Catholic Church in Galicia has had its primatial seat in Santiago de Compostela since the 12th century.


Since the Middle Ages, the Galician Catholic Church has been organized into five ecclesiastical dioceses (Lugo, Ourense, Santiago de Compostela, Mondoñedo-Ferrol and Tui-Vigo). While these may have coincided with contemporary 15th-century civil provinces, they no longer have the same boundaries as the modern civil provincial divisions. The church is led by one archbishop and four bishops. Moreover, of five dioceses, Galicia is divided between 163 districts and 3,792 parishes, a few of which are governed by administrators, the remainder by parish priests.


Hundreds of ancient standing stone monuments like dolmens, menhirs and megalithics Tumulus were erected during the prehistoric period in Galicia, amongst the best-known are the dolmens of Dombate, Corveira, Axeitos of Pedra da Arca, menhirs like the "Lapa de Gargñáns". From the Iron Age, Galicia has a rich heritage based mainly on a great number of Hill forts, few of them excavated like Baroña, Sta. Tegra, San Cibrao de Lás and Formigueiros among others. With the introduction of Ancient Roman architecture there was a development of basilicas, castra, city walls, cities, villas, Roman temples, Roman roads, and the Roman bridge of Ponte Vella. It was the Romans who founded some of the first cities in Galicia like Lugo and Ourense. Perhaps the best-known examples are the Roman Walls of Lugo and the Tower of Hercules in A Coruña.


The patron saint of Galicia is Saint James the Greater, whose body was discovered – according to the Catholic tradition – in 814 near Compostela. After that date, the relics of Saint James became an extraordinary centre of pilgrimage and from the 9th century have been kept in the heart of the church – the modern-day cathedral – dedicated to him. There are many other Galician and associated saints; some of the best-known are: Saint Ansurius, Saint Rudesind, Saint Mariña of Augas Santas, Saint Senorina, Trahamunda and Froilan.


In northern Galicia, the A Coruña-Ferrol metropolitan area has become increasingly dominant in terms of population. The population of the city of A Coruña in 1900 was 43,971. The population of the rest of the province including the City and Naval Station of nearby Ferrol and Santiago de Compostela was 653,556. A Coruña's growth occurred after the Spanish Civil War at the same speed as other major Galician cities, but it was the arrival of democracy in Spain after the death of Francisco Franco when A Coruña left all the other Galician cities behind.


Galicia's inhabitants are known as Galicians (Galician: galegos, Spanish: gallegos). For well over a century Galicia has grown more slowly than the rest of Spain, due largely to emigration to Latin America and to other parts of Spain. Sometimes Galicia has lost population in absolute terms. In 1857, Galicia had Spain's densest population and constituted 11.5% of the national population. As of 2007, only 6.1% of the Spanish population resides in the autonomous community. This is due to an exodus of Galician people since the 19th century, first to South America and later to Central Europe.


The Galician road network includes autopistas and autovías connecting the major cities, as well as national and secondary roads to the rest of the municipalities. The Autovía A-6 connects A Coruña and Lugo to Madrid, entering Galicia at Pedrafita do Cebreiro. The Autovía A-52 connects O Porriño, Ourense and Benavente, and enters Galicia at A Gudiña. Two more autovías are under construction. Autovía A-8 enters Galicia on the Cantabrian coast, and ends in Baamonde (Lugo province). Autovía A-76 enters Galicia in Valdeorras; it is an upgrade of the existing N-120 to Ourense and Vigo.


USB was designed to standardize the connection of computer peripherals (including keyboards, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters) to personal computers, both to communicate and to supply electric power. It has become commonplace on other devices, such as smartphones, PDAs and video game consoles. USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices.


Unlike other data cables (e.g., Ethernet, HDMI), each end of a USB cable uses a different kind of connector; a Type-A or a Type-B. This kind of design was chosen to prevent electrical overloads and damaged equipment, as only the Type-A socket provides power. There are cables with Type-A connectors on both ends, but they should be used carefully. Therefore, in general, each of the different "sizes" requires four different connectors; USB cables have the Type-A and Type-B plugs, and the corresponding receptacles are on the computer or electronic device. In common practice, the Type-A connector is usually the full size, and the Type-B side can vary as needed.


Counter-intuitively, the "micro" size is the most durable from the point of designed insertion lifetime. The standard and mini connectors were designed for less than daily connections, with a design lifetime of 1,500 insertion-removal cycles. (Improved mini-B connectors have reached 5,000-cycle lifetimes.) Micro connectors were designed with frequent charging of portable devices in mind; not only is design lifetime of the connector improved to 10,000 cycles, but it was also redesigned to place the flexible contacts, which wear out sooner, on the easily replaced cable, while the more durable rigid contacts are located in the micro-USB receptacles. Likewise, the springy part of the retention mechanism (parts that provide required gripping force) were also moved into plugs on the cable side.


USB connections also come in five data transfer modes, in ascending order: Low Speed (1.0), Full Speed (1.0), High Speed (2.0), SuperSpeed (3.0), and SuperSpeed+ (3.1). High Speed is supported only by specifically designed USB 2.0 High Speed interfaces (that is, USB 2.0 controllers without the High Speed designation do not support it), as well as by USB 3.0 and newer interfaces. SuperSpeed is supported only by USB 3.0 and newer interfaces, and requires a connector and cable with extra pins and wires, usually distinguishable by the blue inserts in connectors.


A group of seven companies began the development of USB in 1994: Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data rates for external devices. A team including Ajay Bhatt worked on the standard at Intel; the first integrated circuits supporting USB were produced by Intel in 1995.


The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/s "Low Speed" and 12 Mbit/s "Full Speed". Microsoft Windows 95, OSR 2.1 provided OEM support for the devices. The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks. Apple Inc.'s iMac was the first mainstream product with USB and the iMac's success popularized USB itself. Following Apple's design decision to remove all legacy ports from the iMac, many PC manufacturers began building legacy-free PCs, which led to the broader PC market using USB as a standard.


The new SuperSpeed bus provides a fourth transfer mode with a data signaling rate of 5.0 Gbit/s, in addition to the modes supported by earlier versions. The payload throughput is 4 Gbit/s[citation needed] (due to the overhead incurred by 8b/10b encoding), and the specification considers it reasonable to achieve around 3.2 Gbit/s (0.4 GB/s or 400 MB/s), which should increase with future hardware advances. Communication is full-duplex in SuperSpeed transfer mode; in the modes supported previously, by 1.x and 2.0, communication is half-duplex, with direction controlled by the host.


As with previous USB versions, USB 3.0 ports come in low-power and high-power variants, providing 150 mA and 900 mA respectively, while simultaneously transmitting data at SuperSpeed rates. Additionally, there is a Battery Charging Specification (Version 1.2 – December 2010), which increases the power handling capability to 1.5 A but does not allow concurrent data transmission. The Battery Charging Specification requires that the physical ports themselves be capable of handling 5 A of current[citation needed] but limits the maximum current drawn to 1.5 A.


A January 2013 press release from the USB group revealed plans to update USB 3.0 to 10 Gbit/s. The group ended up creating a new USB version, USB 3.1, which was released on 31 July 2013, introducing a faster transfer mode called SuperSpeed USB 10 Gbit/s, putting it on par with a single first-generation Thunderbolt channel. The new mode's logo features a "Superspeed+" caption (stylized as SUPERSPEED+). The USB 3.1 standard increases the data signaling rate to 10 Gbit/s in the USB 3.1 Gen2 mode, double that of USB 3.0 (referred to as USB 3.1 Gen1) and reduces line encoding overhead to just 3% by changing the encoding scheme to 128b/132b. The first USB 3.1 implementation demonstrated transfer speeds of 7.2 Gbit/s.


Developed at roughly the same time as the USB 3.1 specification, but distinct from it, the USB Type-C Specification 1.0 was finalized in August 2014 and defines a new small reversible-plug connector for USB devices. The Type-C plug connects to both hosts and devices, replacing various Type-A and Type-B connectors and cables with a standard meant to be future-proof, similar to Apple Lightning and Thunderbolt. The 24-pin double-sided connector provides four power/ground pairs, two differential pairs for USB 2.0 data bus (though only one pair is implemented in a Type-C cable), four pairs for high-speed data bus, two "sideband use" pins, and two configuration pins for cable orientation detection, dedicated biphase mark code (BMC) configuration data channel, and VCONN +5 V power for active cables. Type-A and Type-B adaptors and cables are required for older devices to plug into Type-C hosts. Adapters and cables with a Type-C receptacle are not allowed.[citation needed]


Full-featured USB Type-C cables are active, electronically marked cables that contain a chip with an ID function based on the configuration data channel and vendor-defined messages (VDMs) from the USB Power Delivery 2.0 specification. USB Type-C devices also support power currents of 1.5 A and 3.0 A over the 5 V power bus in addition to baseline 900 mA; devices can either negotiate increased USB current through the configuration line, or they can support the full Power Delivery specification using both BMC-coded configuration line and legacy BFSK-coded VBUS line.


The design architecture of USB is asymmetrical in its topology, consisting of a host, a multitude of downstream USB ports, and multiple peripheral devices connected in a tiered-star topology. Additional USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels. A USB host may implement multiple host controllers and each host controller may provide one or more USB ports. Up to 127 devices, including hub devices if present, may be connected to a single host controller. USB devices are linked in series through hubs. One hub—built into the host controller—is the root hub.


A physical USB device may consist of several logical sub-devices that are referred to as device functions. A single device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). This kind of device is called a composite device. An alternative to this is compound device, in which the host assigns each logical device a distinctive address and all logical devices connect to a built-in hub that connects to the physical USB cable.


USB device communication is based on pipes (logical channels). A pipe is a connection from the host controller to a logical entity, found on a device, and named an endpoint. Because pipes correspond 1-to-1 to endpoints, the terms are sometimes used interchangeably. A USB device could have up to 32 endpoints (16 IN, 16 OUT), though it's rare to have so many. An endpoint is defined and numbered by the device during initialization (the period after physical connection called "enumeration") and so is relatively permanent, whereas a pipe may be opened and closed.


An endpoint of a pipe is addressable with a tuple (device_address, endpoint_number) as specified in a TOKEN packet that the host sends when it wants to start a data transfer session. If the direction of the data transfer is from the host to the endpoint, an OUT packet (a specialization of a TOKEN packet) having the desired device address and endpoint number is sent by the host. If the direction of the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni-directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts both IN and OUT packets.


When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The data rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.


High-speed USB 2.0 hubs contain devices called transaction translators that convert between high-speed USB 2.0 buses and full and low speed buses. When a high-speed USB 2.0 hub is plugged into a high-speed USB host or hub, it operates in high-speed mode. The USB hub then uses either one transaction translator per hub to create a full/low-speed bus routed to all full and low speed devices on the hub, or uses one transaction translator per port to create an isolated full/low-speed bus per port on the hub.


USB implements connections to storage devices using a set of standards called the USB mass storage device class (MSC or UMS). This was at first intended for traditional magnetic and optical drives and has been extended to support flash drives. It has also been extended to support a wide variety of novel devices as many systems can be controlled with the familiar metaphor of file manipulation within directories. The process of making a novel device look like a familiar device is also known as extension. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.


Though most computers since mid-2004 can boot from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage. Buses such as Parallel ATA (PATA or IDE), Serial ATA (SATA), or SCSI fulfill that role in PC class computers. However, USB has one important advantage, in that it is possible to install and remove devices without rebooting the computer (hot-swapping), making it useful for mobile peripherals, including drives of various kinds (given SATA or SCSI devices may or may not support hot-swapping).


Firstly conceived and still used today for optical storage devices (CD-RW drives, DVD drives, etc.), several manufacturers offer external portable USB hard disk drives, or empty enclosures for disk drives. These offer performance comparable to internal drives, limited by the current number and types of attached USB devices, and by the upper limit of the USB interface (in practice about 30 MB/s for USB 2.0 and potentially 400 MB/s or more for USB 3.0). These external drives typically include a "translating device" that bridges between a drive's interface to a USB interface port. Functionally, the drive appears to the user much like an internal drive. Other competing standards for external drive connectivity include eSATA, ExpressCard, FireWire (IEEE 1394), and most recently Thunderbolt.


Media Transfer Protocol (MTP) was designed by Microsoft to give higher-level access to a device's filesystem than USB mass storage, at the level of files rather than disk blocks. It also has optional DRM features. MTP was designed for use with portable media players, but it has since been adopted as the primary storage access protocol of the Android operating system from the version 4.1 Jelly Bean as well as Windows Phone 8 (Windows Phone 7 devices had used the Zune protocol which was an evolution of MTP). The primary reason for this is that MTP does not require exclusive access to the storage device the way UMS does, alleviating potential problems should an Android program request the storage while it is attached to a computer. The main drawback is that MTP is not as well supported outside of Windows operating systems.


USB mice and keyboards can usually be used with older computers that have PS/2 connectors with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, an adaptor that contains no logic circuitry may be used: the hardware in the USB keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port. These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.


By design, it is difficult to insert a USB plug into its receptacle incorrectly. The USB specification states that the required USB icon must be embossed on the "topside" of the USB plug, which "...provides easy user recognition and facilitates alignment during the mating process." The specification also shows that the "recommended" "Manufacturer's logo" ("engraved" on the diagram but not specified in the text) is on the opposite side of the USB icon. The specification further states, "The USB Icon is also located adjacent to each receptacle. Receptacles should be oriented to allow the icon on the plug to be visible during the mating process." However, the specification does not consider the height of the device compared to the eye level height of the user, so the side of the cable that is "visible" when mated to a computer on a desk can depend on whether the user is standing or kneeling.


The standard connectors were deliberately intended to enforce the directed topology of a USB network: Type-A receptacles on host devices that supply power and Type-B receptacles on target devices that draw power. This prevents users from accidentally connecting two USB power supplies to each other, which could lead to short circuits and dangerously high currents, circuit failures, or even fire. USB does not support cyclic networks and the standard connectors from incompatible USB devices are themselves incompatible.


The standard connectors were designed to be robust. Because USB is hot-pluggable, the connectors would be used more frequently, and perhaps with less care, than other connectors. Many previous connector designs were fragile, specifying embedded component pins or other delicate parts that were vulnerable to bending or breaking. The electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is usually protected by an enclosing metal sheath.


The connector construction always ensures that the external sheath on the plug makes contact with its counterpart in the receptacle before any of the four connectors within make electrical contact. The external metallic sheath is typically connected to system ground, thus dissipating damaging static charges. This enclosure design also provides a degree of protection from electromagnetic interference to the USB signal while it travels through the mated connector pair (the only location when the otherwise twisted data pair travels in parallel). In addition, because of the required sizes of the power and common connections, they are made after the system ground but before the data connections. This type of staged make-break timing allows for electrically safe hot-swapping.


The newer micro-USB receptacles are designed for a minimum rated lifetime of 10,000 cycles of insertion and removal between the receptacle and plug, compared to 1,500 for the standard USB and 5,000 for the mini-USB receptacle. Features intended to accomplish include, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the cable side of the connection. This change was made so that the connector on the less expensive cable would bear the most wear instead of the more expensive micro-USB device. However the idea that these changes did in fact make the connector more durable in real world use has been widely disputed, with many contending that they are in fact, much less durable.


The USB standard specifies relatively loose tolerances for compliant USB connectors to minimize physical incompatibilities in connectors from different vendors. To address a weakness present in some other connector standards, the USB specification also defines limits to the size of a connecting device in the area around its plug. This was done to prevent a device from blocking adjacent ports due to the size of the cable strain relief mechanism (usually molding integral with the cable outer insulation) at the connector. Compliant devices must either fit within the size restrictions or support a compliant extension cable that does.


In general, USB cables have only plugs on their ends, while hosts and devices have only receptacles. Hosts almost universally have Type-A receptacles, while devices have one or another Type-B variety. Type-A plugs mate only with Type-A receptacles, and the same applies to their Type-B counterparts; they are deliberately physically incompatible. However, an extension to the USB standard specification called USB On-The-Go (OTG) allows a single port to act as either a host or a device, which is selectable by the end of the cable that plugs into the receptacle on the OTG-enabled unit. Even after the cable is hooked up and the units are communicating, the two units may "swap" ends under program control. This capability is meant for units such as PDAs in which the USB link might connect to a PC's host port as a device in one instance, yet connect as a host itself to a keyboard and mouse device in another instance.


Various connectors have been used for smaller devices such as digital cameras, smartphones, and tablet computers. These include the now-deprecated (i.e. de-certified but standardized) mini-A and mini-AB connectors; mini-B connectors are still supported, but are not OTG-compliant (On The Go, used in mobile devices). The mini-B USB connector was standard for transferring data to and from the early smartphones and PDAs. Both mini-A and mini-B plugs are approximately 3 by 7 mm; the mini-A connector and the mini-AB receptacle connector were deprecated on 23 May 2007.


The micro plug design is rated for at least 10,000 connect-disconnect cycles, which is more than the mini plug design. The micro connector is also designed to reduce the mechanical wear on the device; instead the easier-to-replace cable is designed to bear the mechanical wear of connection and disconnection. The Universal Serial Bus Micro-USB Cables and Connectors Specification details the mechanical characteristics of micro-A plugs, micro-AB receptacles (which accept both micro-A and micro-B plugs), and micro-B plugs and receptacles, along with a standard-A receptacle to micro-A plug adapter.


The cellular phone carrier group Open Mobile Terminal Platform (OMTP) in 2007 endorsed micro-USB as the standard connector for data and power on mobile devices In addition, on 22 October 2009 the International Telecommunication Union (ITU) has also announced that it had embraced micro-USB as the Universal Charging Solution its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."


The European Standardisation Bodies CEN, CENELEC and ETSI (independent of the OMTP/GSMA proposal) defined a common External Power Supply (EPS) for use with smartphones sold in the EU based on micro-USB. 14 of the world's largest mobile phone manufacturers signed the EU's common EPS Memorandum of Understanding (MoU). Apple, one of the original MoU signers, makes micro-USB adapters available – as permitted in the Common EPS MoU – for its iPhones equipped with Apple's proprietary 30-pin dock connector or (later) Lightning connector.


All current USB On-The-Go (OTG) devices are required to have one, and only one, USB connector: a micro-AB receptacle. Non-OTG compliant devices are not allowed to use the micro-AB receptacle, due to power supply shorting hazards on the VBUS line. The micro-AB receptacle is capable of accepting both micro-A and micro-B plugs, attached to any of the legal cables and adapters as defined in revision 1.01 of the micro-USB specification. Prior to the development of micro-USB, USB On-The-Go devices were required to use mini-AB receptacles to perform the equivalent job.


The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required and by default assumes the role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the Host Negotiation Protocol (HNP) is used to temporarily transfer the host role to the B-device.


USB is a serial bus, using four shielded wires for the USB 2.0 variant: two for power (VBUS and GND), and two for differential data signals (labelled as D+ and D− in pinouts). Non-Return-to-Zero Inverted (NRZI) encoding scheme is used for transferring data, with a sync field to synchronize the host and receiver clocks. D+ and D− signals are transmitted on a twisted pair, providing half-duplex data transfers for USB 2.0. Mini and micro connectors have their GND connections moved from pin #4 to pin #5, while their pin #4 serves as an ID pin for the On-The-Go host/client identification.


USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns. The USB 2.0 specification requires that cable delay be less than 5.2 ns per meter (192 000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).


A unit load is defined as 100 mA in USB 1.x and 2.0, and 150 mA in USB 3.0. A device may draw a maximum of five unit loads from a port in USB 1.x and 2.0 (500 mA), or six unit loads in USB 3.0 (900 mA). There are two types of devices: low-power and high-power. A low-power device (such as a USB HID) draws at most one-unit load, with minimum operating voltage of 4.4 V in USB 2.0, and 4 V in USB 3.0. A high-power device draws, at most, the maximum number of unit loads the standard permits. Every device functions initially as low-power (including high-power functions during their low-power enumeration phases), but may request high-power, and get it if available on the providing bus.


Some devices, such as high-speed external disk drives, require more than 500 mA of current and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power and data, the other for power only) to plug into a computer. With such a cable, a device can draw power from two USB ports simultaneously. However, USB compliance specification states that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered."


The USB Battery Charging Specification Revision 1.1 (released in 2007) defines a new type of USB port, called the charging port. Contrary to the standard downstream port, for which current draw by a connected portable device can exceed 100 mA only after digital negotiation with the host or hub, a charging port can supply currents between 500 mA and 1.5 A without the digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drops its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.


Two types of charging port exist: the charging downstream port (CDP), supporting data transfers as well, and the dedicated charging port (DCP), without data support. A portable device can recognize the type of USB port; on a dedicated charging port, the D+ and D− pins are shorted with a resistance not exceeding 200 ohms, while charging downstream ports provide additional detection logic so their presence can be determined by attached devices. (see ref pg. 2, Section 1.4.5, & Table 5-3 "Resistances"—pg. 29).


The USB Battery Charging Specification Revision 1.2 (released in 2010) makes clear that there are safety limits to the rated current at 5 A coming from USB 2.0. On the other hand, several changes are made and limits are increasing including allowing 1.5 A on charging downstream ports for unconfigured devices, allowing high speed communication while having a current up to 1.5 A, and allowing a maximum current of 5 A. Also, revision 1.2 removes support for USB ports type detection via resistive detection mechanisms.


In July 2012, the USB Promoters Group announced the finalization of the USB Power Delivery ("PD") specification, an extension that specifies using certified "PD aware" USB cables with standard USB Type-A and Type-B connectors to deliver increased power (more than 7.5 W) to devices with larger power demand. Devices can request higher currents and supply voltages from compliant hosts –  up to 2 A at 5 V (for a power consumption of up to 10 W), and optionally up to 3 A or 5 A at either 12 V (36 W or 60 W) or 20 V (60 W or 100 W). In all cases, both host-to-device and device-to-host configurations are supported.


The USB Power Delivery revision 2.0 specification has been released as part of the USB 3.1 suite. It covers the Type-C cable and connector with four power/ground pairs and a separate configuration channel, which now hosts a DC coupled low-frequency BMC-coded data channel that reduces the possibilities for RF interference. Power Delivery protocols have been updated to facilitate Type-C features such as cable ID function, Alternate Mode negotiation, increased VBUS currents, and VCONN-powered accessories.


Sleep-and-charge USB ports can be used to charge electronic devices even when the computer is switched off. Normally, when a computer is powered off the USB ports are powered down, preventing phones and other devices from charging. Sleep-and-charge USB ports remain powered even when the computer is off. On laptops, charging devices from the USB port when it is not being powered from AC drains the laptop battery faster; most laptops have a facility to stop charging if their own battery charge level gets too low.


On Dell and Toshiba laptops, the port is marked with the standard USB symbol with an added lightning bolt icon on the right side. Dell calls this feature PowerShare, while Toshiba calls it USB Sleep-and-Charge. On Acer Inc. and Packard Bell laptops, sleep-and-charge USB ports are marked with a non-standard symbol (the letters USB over a drawing of a battery); the feature is simply called Power-off USB. On some laptops such as Dell and Apple MacBook models, it is possible to plug a device in, close the laptop (putting it into sleep mode) and have the device continue to charge.[citation needed]


The GSM Association (GSMA) followed suit on 17 February 2009, and on 22 April 2009, this was further endorsed by the CTIA – The Wireless Association, with the International Telecommunication Union (ITU) announcing on 22 October 2009 that it had also embraced the Universal Charging Solution as its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."


In June 2009, many of the world's largest mobile phone manufacturers signed an EC-sponsored Memorandum of Understanding (MoU), agreeing to make most data-enabled mobile phones marketed in the European Union compatible with a common External Power Supply (EPS). The EU's common EPS specification (EN 62684:2010) references the USB Battery Charging standard and is similar to the GSMA/OMTP and Chinese charging solutions. In January 2011, the International Electrotechnical Commission (IEC) released its version of the (EU's) common EPS standard as IEC 62684:2011.


Some USB devices require more power than is permitted by the specifications for a single port. This is common for external hard and optical disc drives, and generally for devices with motors or lamps. Such devices can use an external power supply, which is allowed by the standard, or use a dual-input USB cable, one input of which is used for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some USB ports and external hubs can, in practice, supply more power to USB devices than required by the specification but a standard-compliant device may not depend on this.


In addition to limiting the total average power used by the device, the USB specification limits the inrush current (i.e., that used to charge decoupling and filter capacitors) when the device is first connected. Otherwise, connecting a device could cause problems with the host's internal power. USB devices are also required to automatically enter ultra low-power suspend mode when the USB host is suspended. Nevertheless, many USB host interfaces do not cut off the power supply to USB devices when they are suspended.


Some non-standard USB devices use the 5 V power supply without participating in a proper USB network, which negotiates power draw with the host interface. These are usually called USB decorations.[citation needed] Examples include USB-powered keyboard lights, fans, mug coolers and heaters, battery chargers, miniature vacuum cleaners, and even miniature lava lamps. In most cases, these items contain no digital circuitry, and thus are not standard compliant USB devices. This may cause problems with some computers, such as drawing too much current and damaging circuitry. Prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode.


USB data is transmitted by toggling the data lines between the J state and the opposite K state. USB encodes data using the NRZI line coding; a 0 bit is transmitted by toggling the data lines from J to K or vice versa, while a 1 bit is transmitted by leaving the data lines as-is. To ensure a minimum density of signal transitions remains in the bitstream, USB uses bit stuffing; an extra 0 bit is inserted into the data stream after any appearance of six consecutive 1 bits. Seven consecutive received 1 bits is always an error. USB 3.0 has introduced additional data transmission encodings.


A USB packet's end, called EOP (end-of-packet), is indicated by the transmitter driving 2 bit times of SE0 (D+ and D− both below max.) and 1 bit time of J state. After this, the transmitter ceases to drive the D+/D− lines and the aforementioned pull up resistors hold it in the J (idle) state. Sometimes skew due to hubs can add as much as one bit time before the SE0 of the end of packet. This extra bit can also result in a "bit stuff violation" if the six bits before it in the CRC are 1s. This bit should be ignored by receiver.


USB 2.0 devices use a special protocol during reset, called chirping, to negotiate the high bandwidth mode with the host/hub. A device that is HS capable first connects as an FS device (D+ pulled high), but upon receiving a USB RESET (both D+ and D− driven LOW by host for 10 to 20 ms) it pulls the D− line high, known as chirp K. This indicates to the host that the device is high bandwidth. If the host/hub is also HS capable, it chirps (returns alternating J and K states on D− and D+ lines) letting the device know that the hub operates at high bandwidth. The device has to receive at least three sets of KJ chirps before it changes to high bandwidth terminations and begins high bandwidth signaling. Because USB 3.0 uses wiring separate and additional to that used by USB 2.0 and USB 1.x, such bandwidth negotiation is not required.


According to routine testing performed by CNet, write operations to typical Hi-Speed (USB 2.0) hard drives can sustain rates of 25–30 MB/s, while read operations are at 30–42 MB/s; this is 70% of the total available bus bandwidth. For USB 3.0, typical write speed is 70–90 MB/s, while read speed is 90–110 MB/s. Mask Tests, also known as Eye Diagram Tests, are used to determine the quality of a signal in the time domain. They are defined in the referenced document as part of the electrical test description for the high-speed (HS) mode at 480 Mbit/s.


After the sync field, all packets are made of 8-bit bytes, transmitted least-significant bit first. The first byte is a packet identifier (PID) byte. The PID is actually 4 bits; the byte consists of the 4-bit PID followed by its bitwise complement. This redundancy helps detect errors. (Note also that a PID byte contains at most four consecutive 1 bits, and thus never needs bit-stuffing, even when combined with the final 1 bit in the sync byte. However, trailing 1 bits in the PID may require bit-stuffing within the first few bits of the payload.)


Handshake packets consist of only a single PID byte, and are generally sent in response to data packets. Error detection is provided by transmitting four bits that represent the packet type twice, in a single PID byte using complemented form. Three basic types are ACK, indicating that data was successfully received, NAK, indicating that the data cannot be received and should be retried, and STALL, indicating that the device has an error condition and cannot transfer data until some corrective action (such as device initialization) occurs.


IN and OUT tokens contain a seven-bit device number and four-bit function number (for multifunction devices) and command the device to transmit DATAx packets, or receive the following DATAx packets, respectively. An IN token expects a response from a device. The response may be a NAK or STALL response, or a DATAx frame. In the latter case, the host issues an ACK handshake if appropriate. An OUT token is followed immediately by a DATAx frame. The device responds with ACK, NAK, NYET, or STALL, as appropriate.


USB 2.0 also added a larger three-byte SPLIT token with a seven-bit hub number, 12 bits of control flags, and a five-bit CRC. This is used to perform split transactions. Rather than tie up the high-bandwidth USB bus sending data to a slower USB device, the nearest high-bandwidth capable hub receives a SPLIT token followed by one or two USB packets at high bandwidth, performs the data transfer at full or low bandwidth, and provides the response at high bandwidth when prompted by a second SPLIT token.


There are two basic forms of data packet, DATA0 and DATA1. A data packet must always be preceded by an address token, and is usually followed by a handshake token from the receiver back to the transmitter. The two packet types provide the 1-bit sequence number required by Stop-and-wait ARQ. If a USB host does not receive a response (such as an ACK) for data it has transmitted, it does not know if the data was received or not; the data might have been lost in transit, or it might have been received but the handshake response was lost.


Low-bandwidth devices are supported with a special PID value, PRE. This marks the beginning of a low-bandwidth packet, and is used by hubs that normally do not send full-bandwidth packets to low-bandwidth devices. Since all PID bytes include four 0 bits, they leave the bus in the full-bandwidth K state, which is the same as the low-bandwidth J state. It is followed by a brief pause, during which hubs enable their low-bandwidth outputs, already idling in the J state. Then a low-bandwidth packet follows, beginning with a sync sequence and PID byte, and ending with a brief period of SE0. Full-bandwidth devices other than hubs can simply ignore the PRE packet and its low-bandwidth contents, until the final SE0 indicates that a new packet follows.


These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, FireWire 400 is faster than USB 2.0 Hi-Bandwidth in real-use, especially in high-bandwidth use such as external hard-drives. The newer FireWire 800 standard is twice as fast as FireWire 400 and faster than USB 2.0 Hi-Bandwidth both theoretically and practically. However, Firewire's speed advantages rely on low-level techniques such as direct memory access (DMA), which in turn have created opportunities for security exploits such as the DMA attack.


The IEEE 802.3af Power over Ethernet (PoE) standard specifies a more elaborate power negotiation scheme than powered USB. It operates at 48 V DC and can supply more power (up to 12.95 W, PoE+ 25.5 W) over a cable up to 100 meters compared to USB 2.0, which provides 2.5 W with a maximum cable length of 5 meters. This has made PoE popular for VoIP telephones, security cameras, wireless access points and other networked devices within buildings. However, USB is cheaper than PoE provided that the distance is short, and power demand is low.


Ethernet standards require electrical isolation between the networked device (computer, phone, etc.) and the network cable up to 1500 V AC or 2250 V DC for 60 seconds. USB has no such requirement as it was designed for peripherals closely associated with a host computer, and in fact it connects the peripheral and host grounds. This gives Ethernet a significant safety advantage over USB with peripherals such as cable and DSL modems connected to external wiring that can assume hazardous voltages under certain fault conditions.


eSATA does not supply power to external devices. This is an increasing disadvantage compared to USB. Even though USB 3.0's 4.5 W is sometimes insufficient to power external hard drives, technology is advancing and external drives gradually need less power, diminishing the eSATA advantage. eSATAp (power over eSATA; aka ESATA/USB) is a connector introduced in 2009 that supplies power to attached devices using a new, backward compatible, connector. On a notebook eSATAp usually supplies only 5 V to power a 2.5-inch HDD/SSD; on a desktop workstation it can additionally supply 12 V to power larger devices including 3.5-inch HDD/SSD and 5.25-inch optical drives.


USB 2.0 High-Speed Inter-Chip (HSIC) is a chip-to-chip variant of USB 2.0 that eliminates the conventional analog transceivers found in normal USB. It was adopted as a standard by the USB Implementers Forum in 2007. The HSIC physical layer uses about 50% less power and 75% less board area compared to traditional USB 2.0. HSIC uses two signals at 1.2 V and has a throughput of 480 Mbit/s. Maximum PCB trace length for HSIC is 10 cm. It does not have low enough latency to support RAM memory sharing between two chips.


Throughout its prehistory and early history, the region and its vicinity in the Yangtze region was the cradle of unique local civilizations which can be dated back to at least the 15th century BC and coinciding with the later years of the Shang and Zhou dynasties in North China. Sichuan was referred to in ancient Chinese sources as Ba-Shu (巴蜀), an abbreviation of the kingdoms of Ba and Shu which existed within the Sichuan Basin. Ba included Chongqing and the land in eastern Sichuan along the Yangtze and some tributary streams, while Shu included today's Chengdu, its surrounding plain and adjacent territories in western Sichuan.