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Optical character recognition

Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten or printed text into machine-encoded text, whether from a scanned document, a photo of a document, a scene photo (for example the text on signs and billboards in a landscape photo) or from subtitle text superimposed on an image (for example: from a television broadcast).

Widely used as a form of data entry from printed paper data records – whether passport documents, invoices, bank statements, computerized receipts, business cards, mail, printed data, or any suitable documentation – it is a common method of digitizing printed texts so that they can be electronically edited, searched, stored more compactly, displayed online, and used in machine processes such as cognitive computing, machine translation, (extracted) text-to-speech, key data and text mining. OCR is a field of research in pattern recognition, artificial intelligence and computer vision.

Early versions needed to be trained with images of each character, and worked on one font at a time. Advanced systems capable of producing a high degree of accuracy for most fonts are now common, and with support for a variety of image file format inputs. Some systems are capable of reproducing formatted output that closely approximates the original page including images, columns, and other non-textual components.

History
Early optical character recognition may be traced to technologies involving telegraphy and creating reading devices for the blind. In 1914, Emanuel Goldberg developed a machine that read characters and converted them into standard telegraph code. Concurrently, Edmund Fournier d'Albe developed the Optophone, a handheld scanner that when moved across a printed page, produced tones that corresponded to specific letters or characters.

In the late 1920s and into the 1930s, Emanuel Goldberg developed what he called a "Statistical Machine" for searching microfilm archives using an optical code recognition system. In 1931, he was granted US Patent number 1,838,389 for the invention. The patent was acquired by IBM.

Visually impaired users
In 1974, Ray Kurzweil started the company Kurzweil Computer Products, Inc. and continued development of omni-font OCR, which could recognize text printed in virtually any font. (Kurzweil is often credited with inventing omni-font OCR, but it was in use by companies, including CompuScan, in the late 1960s and 1970s. ) Kurzweil used the technology to create a reading machine for blind people to have a computer read text to them out loud. The device included a CCD-type flatbed scanner and a text-to-speech synthesizer. On January 13, 1976, the finished product was unveiled during a widely reported news conference headed by Kurzweil and the leaders of the National Federation of the Blind. In 1978, Kurzweil Computer Products began selling a commercial version of the optical character recognition computer program. LexisNexis was one of the first customers, and bought the program to upload legal paper and news documents onto its nascent online databases. Two years later, Kurzweil sold his company to Xerox, which eventually spun it off as Scansoft, which merged with Nuance Communications.

In the 2000s, OCR was made available online as a service (WebOCR), in a cloud computing environment, and in mobile applications like real-time translation of foreign-language signs on a smartphone. With the advent of smartphones and smartglasses, OCR can be used in internet connected mobile device applications that extract text captured using the device's camera. These devices that do not have built-in OCR functionality will typically use an OCR API to extract the text from the image file captured by the device. The OCR API returns the extracted text, along with information about the location of the detected text in the original image back to the device app for further processing (such as text-to-speech) or display.

Various commercial and open source OCR systems are available for most common writing systems, including Latin, Cyrillic, Arabic, Hebrew, Indic, Bengali (Bangla), Devanagari, Tamil, Chinese, Japanese, and Korean characters.

Applications
OCR engines have been developed into software applications specializing in various subjects such as receipts, invoices, checks, and legal billing documents.

The software can be used for:
 * Entering data for business documents, e.g. checks, passports, invoices, bank statements and receipts
 * Automatic number-plate recognition
 * Passport recognition and information extraction in airports
 * Automatically extracting key information from insurance documents
 * Traffic-sign recognition
 * Extracting business card information into a contact list
 * Creating textual versions of printed documents, e.g. book scanning for Project Gutenberg
 * Making electronic images of printed documents searchable, e.g. Google Books
 * Converting handwriting in real-time to control a computer (pen computing)
 * Defeating or testing the robustness of CAPTCHA anti-bot systems, though these are specifically designed to prevent OCR.
 * Assistive technology for blind and visually impaired users
 * Writing instructions for vehicles by identifying CAD images in a database that are appropriate to the vehicle design as it changes in real time
 * Making scanned documents searchable by converting them to PDFs

Types

 * Optical character recognition (OCR) – targets typewritten text, one glyph or character at a time.
 * Optical word recognition – targets typewritten text, one word at a time (for languages that use a space as a word divider). Usually just called "OCR".
 * Intelligent character recognition (ICR) – also targets handwritten printscript or cursive text one glyph or character at a time, usually involving machine learning.
 * Intelligent word recognition (IWR) – also targets handwritten printscript or cursive text, one word at a time. This is especially useful for languages where glyphs are not separated in cursive script.

OCR is generally an offline process, which analyses a static document. There are cloud based services which provide an online OCR API service. Handwriting movement analysis can be used as input to handwriting recognition. Instead of merely using the shapes of glyphs and words, this technique is able to capture motion, such as the order in which segments are drawn, the direction, and the pattern of putting the pen down and lifting it. This additional information can make the process more accurate. This technology is also known as "online character recognition", "dynamic character recognition", "real-time character recognition", and "intelligent character recognition".

Pre-processing
OCR software often pre-processes images to improve the chances of successful recognition. Techniques include:
 * De-skewing – if the document was not aligned properly when scanned, it may need to be tilted a few degrees clockwise or counterclockwise in order to make lines of text perfectly horizontal or vertical.
 * Despeckling – removal of positive and negative spots, smoothing edges
 * Binarization – conversion of an image from color or greyscale to black-and-white (called a binary image because there are two colors). The task is performed as a simple way of separating the text (or any other desired image component) from the background. The task of binarization is necessary since most commercial recognition algorithms work only on binary images, as it is simpler to do so. In addition, the effectiveness of binarization influences to a significant extent the quality of character recognition, and careful decisions are made in the choice of the binarization employed for a given input image type; since the quality of the method used to obtain the binary result depends on the type of image (scanned document, scene text image, degraded historical document, etc.).
 * Line removal – Cleaning up non-glyph boxes and lines
 * Layout analysis or zoning – Identification of columns, paragraphs, captions, etc. as distinct blocks. Especially important in multi-column layouts and tables.
 * Line and word detection – Establishment of a baseline for word and character shapes, separating words as necessary.
 * Script recognition – In multilingual documents, the script may change at the level of the words and hence, identification of the script is necessary, before the right OCR can be invoked to handle the specific script.
 * Character isolation or segmentation – For per-character OCR, multiple characters that are connected due to image artifacts must be separated; single characters that are broken into multiple pieces due to artifacts must be connected.
 * Normalization of aspect ratio and scale

Segmentation of fixed-pitch fonts is accomplished relatively simply by aligning the image to a uniform grid based on where vertical grid lines will least often intersect black areas. For proportional fonts, more sophisticated techniques are needed because whitespace between letters can sometimes be greater than that between words, and vertical lines can intersect more than one character.

Text recognition
There are two basic types of core OCR algorithm, which may produce a ranked list of candidate characters.

 * Matrix matching involves comparing an image to a stored glyph on a pixel-by-pixel basis; it is also known as pattern matching, pattern recognition, or image correlation. This relies on the input glyph being correctly isolated from the rest of the image, and the stored glyph being in a similar font and at the same scale. This technique works best with typewritten text and does not work well when new fonts are encountered. This is the technique early physical photocell-based OCR implemented, rather directly.
 * Feature extraction decomposes glyphs into "features" like lines, closed loops, line direction, and line intersections. The extraction features reduces the dimensionality of the representation and makes the recognition process computationally efficient. These features are compared with an abstract vector-like representation of a character, which might reduce to one or more glyph prototypes. General techniques of feature detection in computer vision are applicable to this type of OCR, which is commonly seen in "intelligent" handwriting recognition and most modern OCR software. Nearest neighbour classifiers such as the k-nearest neighbors algorithm are used to compare image features with stored glyph features and choose the nearest match.

Software such as Cuneiform and Tesseract use a two-pass approach to character recognition. The second pass is known as adaptive recognition and uses the letter shapes recognized with high confidence on the first pass to better recognize the remaining letters on the second pass. This is advantageous for unusual fonts or low-quality scans where the font is distorted (e.g. blurred or faded).

, modern OCR software includes Google Docs OCR, ABBYY FineReader, and Transym. Others like OCRopus and Tesseract use neural networks which are trained to recognize whole lines of text instead of focusing on single characters.

A technique known as iterative OCR automatically crops a document into sections based on page layout. OCR is performed on the sections individually using variable character confidence level thresholds to maximize page-level OCR accuracy. A patent from the United States Patent Office has been issued for this method.

The OCR result can be stored in the standardized ALTO format, a dedicated XML schema maintained by the United States Library of Congress. Other common formats include hOCR and PAGE XML.

For a list of optical character recognition software, see Comparison of optical character recognition software.

Post-processing
OCR accuracy can be increased if the output is constrained by a lexicon – a list of words that are allowed to occur in a document. This might be, for example, all the words in the English language, or a more technical lexicon for a specific field. This technique can be problematic if the document contains words not in the lexicon, like proper nouns. Tesseract uses its dictionary to influence the character segmentation step, for improved accuracy.

The output stream may be a plain text stream or file of characters, but more sophisticated OCR systems can preserve the original layout of the page and produce, for example, an annotated PDF that includes both the original image of the page and a searchable textual representation.

Near-neighbor analysis can make use of co-occurrence frequencies to correct errors, by noting that certain words are often seen together. For example, "Washington, D.C." is generally far more common in English than "Washington DOC".

Knowledge of the grammar of the language being scanned can also help determine if a word is likely to be a verb or a noun, for example, allowing greater accuracy.

The Levenshtein Distance algorithm has also been used in OCR post-processing to further optimize results from an OCR API.

Application-specific optimizations
In recent years, the major OCR technology providers began to tweak OCR systems to deal more efficiently with specific types of input. Beyond an application-specific lexicon, better performance may be had by taking into account business rules, standard expression, or rich information contained in color images. This strategy is called "Application-Oriented OCR" or "Customized OCR", and has been applied to OCR of license plates, invoices, screenshots, ID cards, driver's licenses, and automobile manufacturing.

The New York Times has adapted the OCR technology into a proprietary tool they entitle Document Helper, that enables their interactive news team to accelerate the processing of documents that need to be reviewed. They note that it enables them to process what amounts to as many as 5,400 pages per hour in preparation for reporters to review the contents.

Workarounds
There are several techniques for solving the problem of character recognition by means other than improved OCR algorithms.

Forcing better input
Special fonts like OCR-A, OCR-B, or MICR fonts, with precisely specified sizing, spacing, and distinctive character shapes, allow a higher accuracy rate during transcription in bank check processing. Several prominent OCR engines were designed to capture text in popular fonts such as Arial or Times New Roman, and are incapable of capturing text in these fonts that are specialized and very different from popularly used fonts. As Google Tesseract can be trained to recognize new fonts, it can recognize OCR-A, OCR-B and MICR fonts.

Comb fields are pre-printed boxes that encourage humans to write more legibly – one glyph per box. These are often printed in a dropout color which can be easily removed by the OCR system.

Palm OS used a special set of glyphs, known as Graffiti, which are similar to printed English characters but simplified or modified for easier recognition on the platform's computationally limited hardware. Users would need to learn how to write these special glyphs.

Zone-based OCR restricts the image to a specific part of a document. This is often referred to as Template OCR.

Crowdsourcing
Crowdsourcing humans to perform the character recognition can quickly process images like computer-driven OCR, but with higher accuracy for recognizing images than that obtained via computers. Practical systems include the Amazon Mechanical Turk and reCAPTCHA. The National Library of Finland has developed an online interface for users to correct OCRed texts in the standardized ALTO format. Crowd sourcing has also been used not to perform character recognition directly but to invite software developers to develop image processing algorithms, for example, through the use of rank-order tournaments.

Accuracy
Commissioned by the U.S. Department of Energy (DOE), the Information Science Research Institute (ISRI) had the mission to foster the improvement of automated technologies for understanding machine printed documents, and it conducted the most authoritative of the Annual Test of OCR Accuracy from 1992 to 1996.

Recognition of typewritten, Latin script text is still not 100% accurate even where clear imaging is available. One study based on recognition of 19th- and early 20th-century newspaper pages concluded that character-by-character OCR accuracy for commercial OCR software varied from 81% to 99%; total accuracy can be achieved by human review or Data Dictionary Authentication. Other areas – including recognition of hand printing, cursive handwriting, and printed text in other scripts (especially those East Asian language characters which have many strokes for a single character) – are still the subject of active research. The MNIST database is commonly used for testing systems' ability to recognize handwritten digits.

Accuracy rates can be measured in several ways, and how they are measured can greatly affect the reported accuracy rate. For example, if word context (a lexicon of words) is not used to correct software finding non-existent words, a character error rate of 1% (99% accuracy) may result in an error rate of 5% or worse if the measurement is based on whether each whole word was recognized with no incorrect letters. Using a large enough dataset is important in a neural-network-based handwriting recognition solutions. On the other hand, producing natural datasets is very complicated and time-consuming.

An example of the difficulties inherent in digitizing old text is the inability of OCR to differentiate between the "long s" and "f" characters.

Web-based OCR systems for recognizing hand-printed text on the fly have become well known as commercial products in recent years (see Tablet PC history). Accuracy rates of 80% to 90% on neat, clean hand-printed characters can be achieved by pen computing software, but that accuracy rate still translates to dozens of errors per page, making the technology useful only in very limited applications.

Recognition of cursive text is an active area of research, with recognition rates even lower than that of hand-printed text. Higher rates of recognition of general cursive script will likely not be possible without the use of contextual or grammatical information. For example, recognizing entire words from a dictionary is easier than trying to parse individual characters from script. Reading the Amount line of a check (which is always a written-out number) is an example where using a smaller dictionary can increase recognition rates greatly. The shapes of individual cursive characters themselves simply do not contain enough information to accurately (greater than 98%) recognize all handwritten cursive script.

Most programs allow users to set "confidence rates". This means that if the software does not achieve their desired level of accuracy, a user can be notified for manual review.

An error introduced by OCR scanning is sometimes termed a scanno (by analogy with the term typo).

Unicode
Characters to support OCR were added to the Unicode Standard in June 1993, with the release of version 1.1.

Some of these characters are mapped from fonts specific to MICR, OCR-A or OCR-B.

title: Optical character recognition


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Tom Clancy's Rainbow Six (video game)

Tom Clancy's Rainbow Six is a 1998 tactical shooter video game developed and published by Red Storm Entertainment for Microsoft Windows, with later ports for the Nintendo 64, PlayStation, Mac OS, Game Boy Color, and Dreamcast. It is the first installment in the Rainbow Six series. Based on the Tom Clancy novel of the same name, the game follows Rainbow, a secret international counterterrorist organization, and the conspiracy they unravel as they handle a seemingly random spike in terrorism.

In singleplayer, the player advances through a series of missions in a campaign. Before each mission, the player is briefed on the situation, selects and organizes their operatives and equipment, and plans their movement through the level; during missions, the player controls an operative leading computer-controlled teammates as they follow the player's plan. In multiplayer, players cooperate in player versus environment missions or battle to complete objectives in player versus player matches. The game features realistic gameplay factors, weapon lethality, and consequences for failure, forcing players to plan their approach carefully and promoting replayability for more streamlined completion.

Rainbow Six began as a concept by Red Storm following their formation in 1996. The game was developed in parallel with the Rainbow Six novel, with a design philosophy of realism and strategy guiding all aspects of development; however, numerous setbacks stymied the game's development and forced the developers to crunch. Though his name is in the game's title, Tom Clancy's involvement in Rainbow Six 's development was very minimal. Red Storm developed the PC version, while all other ports were developed by their respective companies.

Rainbow Six was released on August 21, 1998 to widespread critical acclaim, though the console ports received relatively lower ratings than the PC version. For most releases, praise was directed toward gameplay, multiplayer, immersion, and the game's combination of strategy and action, while criticism mainly centered on AI issues, glitches, and the graphics and controls of some ports. The game sold over 200,000 copies in its first year of release and continued to sell hundreds of thousands more copies well into the early 2000s. Rainbow Six was nominated for numerous accolades and has been deemed one of the best video games of 1998. It is considered a milestone in the history of first-person shooters and made a lasting impact on the then-fledgling tactical shooter genre.

An expansion pack, Tom Clancy's Rainbow Six Mission Pack: Eagle Watch, was released on January 26, 1999. A sequel, Tom Clancy's Rainbow Six: Rogue Spear, was released in 1999. A loose mobile game remake, Tom Clancy's Rainbow Six: Shadow Vanguard, was released in 2011.

Gameplay

Rainbow Six is a tactical shooter, in which characters are affected by realistic factors and can be killed with a single bullet; therefore, wise tactics and planning are encouraged to complete missions over sheer force and firepower.

The game follows a campaign of several missions, with the plot being advanced in the mission briefing of each. Missions in each version differ: the PC, PlayStation, and Game Boy Color versions have 16 missions, the Nintendo 64 port has 12 missions, and the Dreamcast port has 21 missions. Objectives in missions include defeating enemies, rescuing hostages, defusing bombs, gathering intelligence, and planting surveillance devices. Players are encouraged to find their own ways to complete objectives using a variety of tactics and methods, ranging from stealthy infiltration to a frontal assault (except in missions where stealth is mandatory). Successful missions often last just minutes, but may require dozens of repetitions and planning changes to account for failures, new plans, or simply faster or cleaner completion.

Before each mission is a planning stage, in which the player is briefed on the situation, chooses the Rainbow operatives to be involved in the mission, organizes them into color-coded teams, and selects their weapons, equipment, and uniforms. Operatives are categorized into five classes based on their skill specializations: Assault, Demolitions, Electronics, Recon, and Sniper. The vast majority of operatives are named characters with their own backstories and skillsets, but generic "reserves" are also available for each class should players wish to avoid risking named operatives, although they have greatly reduced skills. In the planning stage, the player is shown a map of the area of operations to set team orders, such as AI pathing, team "go" codes to hold until ordered, where AI operatives will deploy equipment such as flashbangs or door breaching charges, and rules of engagement; alternatively, the player can skip this by choosing to follow a preset plan instead.

During gameplay, the player directly controls a team leader, and can use their weapons and equipment, manually lead their team, and see stats for the controlled operative and their team on the HUD. The player can take control of any alive team leader at will. Operatives and teams not under player control follow the orders given to them in the planning stage. Injured or fatigued operatives require time off after a mission to recover (they can still be used, just with lower health or reduced skills), while deceased operatives are permanently lost and cannot be used for the rest of the campaign playthrough, forcing players to plan carefully to avoid casualties.

Online multiplayer for the PC version was available on the MPlayer.com and Zone.com services. Multiplayer modes include cooperative modes, deathmatch, and team deathmatch, among others. Most other console ports lack multiplayer, though the Nintendo 64 port includes a two-player split-screen cooperative mode.

Most versions of Rainbow Six have only minimal differences to each other, such as the PlayStation port displaying the player's equipped weapon in their hands or the Nintendo 64 port having a different, simpler HUD. The Game Boy Color port is the only exception, having radically different gameplay and presentation due to the platform's technical limitations: gameplay is slowed and simplified, crossfire is removed, and the 3D graphics from other releases are replaced by a 2.5D top-down perspective.

Plot
In 1999, in response to a post-Cold War rise in terrorism, the world's military, law enforcement, and intelligence agencies form "Rainbow", a top secret international counterterrorist organization led by John Clark.

In 2000, Rainbow responds to a series of terrorist attacks linked to the Phoenix Group eco-terrorist organization. Rainbow's operations against Phoenix are assisted by John Brightling, chairman of the powerful biotechnology corporation Horizon Inc., whose facilities are frequently targeted by Phoenix; Anne Lang, the Science Advisor to the President of the United States and an acquaintance of Brightling; and Catherine Winston, a biological expert working with Horizon who is rescued by Rainbow following an attack in the Democratic Republic of the Congo.

After a raid on a Phoenix compound in Idaho that reveals unethical human experimentation, Rainbow learns the Phoenix Group is a front for Horizon. Viewing humanity as an environmentally destructive "disease", Brightling plans to exterminate most of humanity using a highly contagious manmade strain of the Ebola virus called "Brahma", sparing only his chosen few (including Lang), who will rebuild Earth into a scientific environmental utopia. To achieve this, Brightling has engineered terrorist attacks to exploit heightened terrorism concerns and secure a contract for his private security firm Global Security at the 2000 Summer Olympics in Sydney. Global Security's personnel, led by William Hendrickson, will then release Brahma at the Olympics, spreading the virus across the world when the athletes and spectators return home.

After gathering intelligence and rescuing Winston from a last-ditch attempt to silence her, Rainbow apprehends Lang and Hendrickson and prevents Brahma's release at the Olympic Village, foiling Brightling's plans. Brightling and his collaborators flee to their Horizon Ark facility in the Amazon rainforest, where they planned to weather out the Brahma pandemic. Rainbow assaults the Ark, neutralizes Brightling's collaborators, and takes Brightling into custody.

Development
The idea of the game that would become Rainbow Six originated from early concepts Red Storm Entertainment had conceived following the company's formation in 1996. Selected from around 100 other ideas, the original concept, titled HRT, followed the FBI Hostage Rescue Team rescuing hostages from criminals and terrorists. HRT was gradually expanded in scope with the addition of covert operations and an international setting, and the game was rechristened Black Ops. With the initial FBI HRT concept dropped and gameplay branching away from just hostage rescue, multiple alternate settings were proposed for Black Ops—including World War II, 1960s spy fiction-esque Cold War espionage, the near future, and a dystopian antihero-centered story called Jackbooted Thugs—before finally settling on contemporary counterterrorism. Red Storm CEO Doug Littlejohns, a former Royal Navy submarine commander and a close friend of Tom Clancy, did not want to develop an arcade shooter with "mindless violence", but also did not want a "boring" slow-paced strategy game, so Black Ops was designed to focus on realism and action, with a strong emphasis on planning and strategy. Lead game designer Brian Upton, recalling Rainbow Six 's development process in the May 1999 issue of Game Developer, described the game's design philosophy from the initial concept:"We knew from the start that we wanted to capture the excitement of movies such as Mission: Impossible and The Dirty Dozen — the thrill of watching a team of skilled specialists pull off an operation with clockwork precision. We also knew that we wanted it to be an action game with a strong strategic component — a realistic shooter that would be fun to play even without a Quake player's twitch reflexes."Rainbow Six—both the game and the novel—originated from a discussion between Littlejohns and Clancy during a Red Storm company outing in 1996, when Littlejohns mentioned Black Ops. When Clancy mentioned that he was writing his own novel about a hostage rescue unit, their conversation led to Littlejohns noting the protracted diplomatic delays in authorizing a foreign counterterrorist unit's deployment overseas, and he suggested the formation of a permanent counterterrorist unit that already had authorization to deploy internationally. The name "Rainbow" came from the term "Rainbow nation", coined by Desmond Tutu to describe post-apartheid South Africa under Nelson Mandela's presidency. "Six" came from the American rank code for captain (O-6); though John Clark would more accurately be described as a major general (O-8), "Rainbow Six" read better than "Rainbow Eight". Upton objected to the addition of "Six", believing having a number at the end of the title would affect a potential sequel, but he was overruled.

Following the game's development doctrine of realism, lead level designer John Sonedecker designed each level to be as accurate and realistic to real-world architecture as possible, noting that the presence of unusual design elements seen in other less-realistic shooters, such as unnecessarily large doorways or building layouts seemingly designed for combat, would ruin the player's immersion and affect gameplay. The development team had access to counterterrorism experts, military trainers, and technical consultants, and used their advice to ensure authenticity and streamline development by cutting mechanics deemed unrealistic or unnecessary, such as jumping. These technical advisors also provided motion capture for character animations.

By 1997, the game was very behind on schedule, and the developers began to crunch. Many developers slept in a spare room of the office, Upton's mental health deteriorated to the point that he had a nervous breakdown that prompted company restructuring to reduce his workload, and network programmer Dave Weinstein (hired as part of the aforementioned company restructuring) was once stopped by police on suspicion of driving under the influence due to his severe exhaustion from crunch. Clancy's involvement in development was "minimal", only sending Red Storm an early manuscript of the novel to work plot details into the game (hence why the game's plot features different characters and a slightly different storyline). Clancy would insist the developers add features his experts claimed were realistic, such as the fictional heartbeat sensor used in the novel that functions as a radar-like equipment item in-game. In November 1997, the developers realized the game was becoming too demanding, only having single-digit frame rates on high-end devices, so a massive two-month overhaul was ordered. Despite these setbacks, development managed to progress relatively smoothly overall, and a gameplay demonstration at E3 1998 that unintentionally displayed AI teammates rescuing hostages by themselves boosted the game's publicity ahead of release.

Several weeks prior to the game's release on PC, early copies of the game were leaked onto online piracy websites. The users that uploaded the game files reportedly "took credit for 'cracking' a game with no copy protection in it", frustrating the developers; Weinstein recalled going on a profanity-laden rant on the topic in Red Storm's office, only to be pulled aside by Littlejohns for his volume, having been heard three offices away.

The Nintendo 64, PlayStation, Mac OS, Game Boy Color, and Dreamcast releases of the game were each developed by separate companies: Saffire for the N64, Rebellion Developments for the PS1, Varcon Systems for Mac OS, Crawfish Interactive for the GBC, and Pipe Dream Interactive for the Dreamcast. Saffire struggled to simplify Rainbow Six 's control scheme to suit the Nintendo 64 controller and ultimately had to completely remake the game so it would be able to run without frame rate dips on the N64. Crawfish opted to give the Game Boy Color port a unique game style, as they felt other game styles would not suit Rainbow Six 's gameplay and features on the platform. The release of Pipe Dream's Dreamcast port was delayed by eight months.

The game's box art, featuring a Rainbow operative armed with a Heckler & Koch USP, was not created for the game and is actually a modified 1992 photograph of Heckler & Koch USA sales executive John T. Meyer. The original image was used to promote the American launch of the USP in 1993. Heckler & Koch permitted the use of the image for the game and sent firearms instructors to assist with motion capture.

Release
Tom Clancy's Rainbow Six was released for Windows on August 21, 1998, in North America and on October 23, 1998, in Europe. In North America, the game was released by Red Storm Entertainment, with SouthPeak Games handling distribution duties. Take-Two Interactive published the game in Europe. The Nintendo 64 port was released in North America on November 17, 1999, and in the United Kingdom one month later on December 10. The PlayStation conversion was released in the United Kingdom on November 19, and in North America on November 23. A port for Mac OS was released on December 1, 1999. A distinct version of the game was released for Game Boy Color in North America April 12, 2000, and in the United Kingdom on November 10, 2000. The Dreamcast port was delayed several times before releasing. Initially expected to release on September 9, 1999, as a launch title for the system, it was delayed due to the difficulties of working with Windows CE during development. The port was initially delayed to October 19, 1999, before being postponed a month again. It then went gold on November 30, 1999, with an expected release date of December 9, and was released five months later on May 3, 2000, in North America by Majesco Sales' publishing label Pipe Dream Interactive, and on February 2, 2001, in the United Kingdom by German publisher Swing! Entertainment.

After the release of the game, Tom Clancy offered to sign copies of the game for Red Storm employees, despite being relatively uninvolved in development, annoying several developers; as Upton opined, "Even though it had his name on the box, it wasn't his game. It was our game. He should have been asking us to sign a copy for him!"

The PAL PlayStation port of the game was one of 20 games preloaded on the PlayStation Classic (excluding the Japan, Taiwan, and Hong Kong releases), released on December 3, 2018.

Rainbow Six Mission Pack: Eagle Watch
Tom Clancy's Rainbow Six Mission Pack: Eagle Watch is an expansion pack of the original game, released exclusively for Windows in North America on January 26, 1999, before reaching store shelves on January 28, and in Europe in February 1999. It adds five new missions, four new operatives from the Rainbow Six novel, three new weapons, and new multiplayer modes. The new missions, unrelated to each other or the original campaign, take place in 2001 and follow Rainbow's high-profile operations in landmark locations around the world, namely the Buran spaceplane in Russia, the Taj Mahal in India, the Forbidden City in China, the Palace of Westminster in the United Kingdom, and the Capitol in the United States. The expansion was packaged with the original game as Tom Clancy's Rainbow Six: Gold Pack Edition when it released in 1999 in North America in June and in the United Kingdom in September. Some versions of the game also include missions from Eagle Watch, such as the Nintendo 64 port, which includes three.

Reception
Tom Clancy's Rainbow Six was met with mostly positive reviews on PC, though the console ports received relatively lower ratings. Review aggregator Metacritic displays a score of 85 out of 100 for the PC version. Video game review aggregator GameRankings displays scores of 82% for PC, 74% for the Nintendo 64, 48% for the PlayStation, 54% for the Game Boy Color, and 73% for the Dreamcast.

Overall gameplay was positively received. The game's difficulty and playstyle differences to contemporary shooters such as Quake II and GoldenEye 007 were highlighted by multiple reviewers, as was the detailed planning stage. Trent C. Ward, reviewing the PC version for IGN, praised the complexities of the planning stage, realistic damage, competent AI, and freedom to complete missions from multiple approaches, saying it was "unlike any first-person shooter yet made." PC Gamer US called the game "an enthralling package loaded to the brim with tense, nail-biting gameplay, slick technology, and excellent replayability" and "undoubtedly one of the most original and best games of the year." Jeremy Dunham of IGN, reviewing the Dreamcast port, praised the game's change in pace, saying, "Long exposed to mindless romps and pointless first-person gore-fest clones, the ability to actually think and THEN destroy puts a big ol' smile on my face." Push Square Sam Brooke, reviewing the PlayStation port in a 2018 retrospective, enjoyed the sense of accomplishment from completing challenging missions properly, calling it "a trailblazer in its genre". Alan Dunkin of GameSpot noted the game could be difficult, but to the point of sometimes being frustrating.

Several reviews highlighted the game's realism and immersion. Dunkin stated "the immersive feeling of Rainbow Six is perhaps one of the best seen in a game." Christian Nutt, reviewing the Nintendo 64 port for GameSpot, said of Rainbow Six, "realism is the order of the day ... this game does deliver a military simulation on a very personal level." Next Generation commended the game's attempts at realism, but noted flaws in presentation such as the odd manner in which characters leaned around corners.

Multiplayer was singled out for praise, especially for the PC version. Ward praised the multiplayer functionality and its addictiveness, adding that "[f]or weeks now, the offices here have literally shut down as teams from IGN-PC, PC Gamer and PC Accelerator stop what they're doing to take each other on in a team deathmatch, or to cooperate on a difficult mission." Dunkin opined that the multiplayer "saves the game" from its other flaws. PC Gamer US favorably described the multiplayer functionality as "tense and exciting", but suggested the quick time-to-kill could make smaller matches simple and boring. Peter Olafson of GamePro said the multiplayer was "a nice-looking shooter" but criticized lag issues.

AI issues and glitches were subject to considerable criticism. Raphael Liberatore, reviewing the game for Computer Gaming World, criticized "faulty AI and game-killing bugs" for impeding "what could have been a benchmark game—a game troubled by what it could have been." Olafson singled out the lack of variation in AI behavior, with enemies idling and teammates only moving in single-file lines. Brooke criticized AI pathfinding through narrow corridors, recounting one mission where it took longer to extract a hostage than it did to find them in the first place. Ward also recalled experiencing several glitches and instances of teammates obstructing him, but opined such issues could easily be overlooked during gameplay.

Console ports
The Nintendo 64 port was well-received by most reviewers. Aaron Boulding of IGN said the only issue with the port was the shortened campaign, but Nutt considered the short length to be acceptable, viewing the multiple difficulty levels and the co-op mode as making up for it. Electronic Gaming Monthly highlighted the port's detailed graphics yet smooth framerate as impressive for the Nintendo 64, especially without having to resort to render fog. Mike Wolf of Next Generation gave it three stars out of five, stating that though it was "a fantastic game", its flaws meant it was "not a must-have". In a 2018 retrospective, N64 Today said the port still stood up 20 years after its release, but noted noticeable graphical issues, especially if not played on a CRT display.

The PlayStation port was widely panned as inferior to other versions. Official U.S. PlayStation Magazine gave it one star out of five. Nutt lambasted it as "awkward" and "aesthetically bankrupt", noting its apparent abandonment of the team leadership aspect, deeming it "an uninspired FPS with some weird hostage-saving minigame tacked on." IGN 's Matt White criticized its unusually poor graphics, and called it "a mighty fine example for impressionable young developers of how not to handle a port." Brooke called the PlayStation port "janky" and "unpolished", but gave it credit for the game's influence.

The Game Boy Color version received mixed reviews. IGN 's Craig Harris criticized it for removing risk factors such as enemy effectiveness and crossfire, thus making most planning and tactics worthless, though he commended Crawfish Interactive's ambition in adapting a three-dimensional shooter to a two-dimensional handheld. Frank Provo of GameSpot criticized AI issues, gameplay repetition, and noticeable reuse of sprites and sounds, but still considered it a faithful version for what it was.

The Dreamcast port was very well-received. Garrett Kenyon of Next Generation gave it four stars out of five, calling it "[a]n impressive PC translation that Dreamcast owners should certainly consider owning." Erik Wolpaw, reviewing the Dreamcast port for GameSpot, stated it was a faithful port of the PC game and "as deep and challenging as action games get", though he criticized its long loading times, lack of multiplayer, and unusually complex method of issuing commands—over 35 exist, but require specific combinations of joystick and button inputs. Dunham had the same criticisms, noting these issues still existed in the final release despite an eight-month delay in the port's development, but nonetheless deemed it "one of the deepest, most realistic games to inhabit the Dreamcast so far."

Eagle Watch
Mike Lohrey of IGN reviewed the Eagle Watch expansion, praising its new levels and additions but criticizing AI awareness issues and inconsistent damage mechanics compared to the original game. Liberatore, who had previously panned the original game, rated Eagle Watch 4.5 out of 5, stating it "vastly improved the original, AI included, making R6 the standout title it deserves to be."

Accolades
The Academy of Interactive Arts & Sciences nominated Rainbow Six for "PC Action Game of the Year" during the 2nd Annual Interactive Achievement Awards, but it lost to Half-Life. Rainbow Six was a finalist for Computer Gaming World's 1998 "Best Action" award, which ultimately went to Battlezone. The editors wrote that Rainbow Six "deftly mixed strategic planning with nail-biting action as it brought the world of counterterrorist operations to life." PC Gamer US named Rainbow Six the best action game of 1998. CNN, in partnership with Games.net, named Rainbow Six one of the "top 25 game downloads of 1998".

Sales
In the United States, Rainbow Six Windows release sold 218,183 copies during 1998, accounting for $8.86 million in revenue that year. The PC version's Gold Edition release sold another 321,340 copies in the United States during 1999, and was the country's 12th best-selling computer game that year. According to Gamasutra, Rainbow Six and Rainbow Six: Rogue Spear together sold 450,000 copies "during the first half of the 2001/2002 fiscal year".

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Tom Clancy's Rainbow Six (video game)


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Danny Kass

Daniel "Danny" Kass (born September 21, 1982) is an American professional snowboarder who has competed at the Olympic level. In Snowboarding at the 2002 Winter Olympics, Kass won silver in the Men's Halfpipe.

Career
Kass was born in Pompton Plains, New Jersey. He was raised in the Scenic Lakes section of Vernon Township, New Jersey, and attended Vernon Township High School. He began snowboarding in the area at the age of twelve. His home slopes are what are now known as Hidden Valley and Mountain Creek ski resorts, both located in the mountains of Vernon Township and Highland Lakes. After several years of shredding around the Mid-Atlantic States, Kass entered the Okemo Mountain School in Vermont. In 2001, Kass broke out into what has become one of the most successful contest streaks in snowboarding with four US Open Championships, seven Winter X Games medals and two Olympic silver medals.

During the winter of 2006, Kass fought his way back from a slow start in the US Grand Prix Circuit to qualify for the Olympics in Torino for the second time in a row. Kass took home another silver medal with back-to-back 1080s and his signature smooth style.

Kass and his brother Matt Kass were the founders of Grenade Gloves, which specializes in snowboarding gloves, accessories, and other extreme sporting gear.

Kass is one of the stars of The Adventures of Danny and The Dingo on Fuel TV. He also has a podcast with Luke "The Dingo" Trembath on the Monster Energy's YouTube channel, called Unleashed.

title: Danny Kass


text:
University of Minnesota system

The University of Minnesota system is a public university system with five campuses spread across the U.S. state of Minnesota.

The university's campuses are in the Twin Cities, Crookston, Duluth, Morris, and Rochester. The university also operates several research facilities around the state, including some large parcels of land. The University of Minnesota Twin Cities, Crookston, Duluth, Morris and Rochester campuses are accredited by the Higher Learning Commission (HLC). The other public system of higher education in the state is the larger Minnesota State Colleges and Universities system (Minnesota State System, previously MnSCU).

The university has one of the largest endowments among public universities in the U.S., and also receives annual funding from the State of Minnesota.

Campuses
The flagship Twin Cities campus is the largest in the system, with a total enrollment of 50,943 students (undergraduate, graduate, professional, and non-degree included) in fall 2018. In the same year Crookston had 2,810, Duluth had 11,040, Morris had 1,554, and Rochester had 533, bringing the system-wide total to 66,880.

The colors of the university, which are used system-wide, are maroon and gold.

Twin Cities
The University of Minnesota - Twin Cities (UMTC) is the largest with locations in Minneapolis and neighboring Saint Paul (actually, the suburb of Falcon Heights). The locations are connected via a dedicated bus transitway. The buildings on each campus are connected by a series of tunnels and above-ground skyways called The Gopher Way. The campus is the oldest and largest in the system and has the ninth-largest main campus student body in the United States, with 52,376 students at the start of the 2021–22 academic year.

The Minneapolis portion is the largest and has a number of colleges dedicated to a variety of subjects. The Twin Cities campus located in Minneapolis can be further subdivided into the East Bank (main portion) and West Bank, as the Mississippi River flows through it. Students become well-acquainted with the double-decker Washington Avenue Bridge that connects the two sections. There are a number of distinguished graduate and professional schools on the Minneapolis campus, notably the College of Science and Engineering, University of Minnesota Law School, Medical School, Carlson School of Management, School of Public Health, and Hubert H. Humphrey Institute of Public Affairs. In addition, Minneapolis houses many research facilities such as The Cancer Center.

The Twin Cities campus located in St Paul is home to the University of Minnesota College of Food, Agricultural and Natural Resource Sciences, University of Minnesota College of Design, and University of Minnesota College of Biological Sciences programs, the University of Minnesota School of Social Work, the College of Veterinary Medicine, and a variety of additional programs and student services. The Bell Museum of Natural History is also located on the campus in St. Paul.

The mascot for the Twin Cities campus is Goldy Gopher, and the sports teams are called the Minnesota Golden Gophers. They participate in the NCAA's Division I and the football team participates in the Football Bowl Subdivision (FBS). The majority of the teams compete in the Big Ten Conference, however, the women's hockey program competes in the Western Collegiate Hockey Association.

Among the graduates from this campus are two former U.S. Vice Presidents, Hubert Humphrey and Walter Mondale, former NAACP president Roy Wilkins, British Deputy Prime Minister Nick Clegg, several Nobel prize winners, several athletes such as Ric Flair, Kevin McHale, Dave Winfield, Patty Berg, Brock Lesnar, Curt Hennig, Shelton Benjamin, Bobby Jackson of the NBA, and composer Yanni. Folksinger Bob Dylan famously attended the University and was a part of its thriving "West Bank" music scene, but did not graduate. A wide variety of medical and technological innovations have taken place there as well. For instance, the Internet Gopher protocol was created at the Twin Cities campus. A predecessor of sorts to the World Wide Web, it was named after the school mascot.

Campus media includes the Minnesota Daily newspaper, The Wake Student Magazine, and 770 Radio K (KUOM), an AM radio station that is probably the oldest in the state.

Crookston
The University of Minnesota Crookston (UMC) joined the university system in 1966. At that time it was known as the University of Minnesota Technical Institute at Crookston. Since 1993 the Crookston campus has offered bachelor's degrees, and it has grown to be a more comprehensive regional college campus. It is known for its focus on experiential learning and technology, and through fees each student is provided a laptop computer as part of their experience. The campus mascot is Regal the Eagle, and the athletics teams are known as the Golden Eagles.

Duluth
The University of Minnesota Duluth (UMD) became part of the system in 1947, though the campus has a history stretching back to 1895 when it was formed as the Normal School at Duluth. UMD integrates liberal education, research, creative activity, and public engagement and prepares students to thrive as lifelong learners and globally engaged citizens.

Its men's hockey program competes in the National Collegiate Hockey Conference and its women's hockey program competes in the Western Collegiate Hockey Association. UMD baseball, men's and women's basketball, men's and women's cross country, football, men's and women's track and field, soccer, softball, tennis, and volleyball are Division II teams. Their teams are nicknamed Bulldogs. and their mascot is Champ.

Among the graduates from UMD are former Lieutenant Governor of Minnesota Yvonne Prettner Solon, current Duluth mayor Emily Larson, and former Duluth mayor Don Ness. Brian Kobilka received the 2012 Nobel Prize in chemistry. UMD has produced numerous professional hockey players including John Harrington and Mark Pavelich from the 1980 Miracle on Ice Olympic hockey team, and NHL Hall of Famer Brett Hull.

Campus media includes The Bark newspaper; until 2021, UMD also owned radio station KUMD-FM (now WDSE-FM).

Morris
The University of Minnesota Morris (UMM) joined the system in 1960. UMN Morris is a public liberal arts college.

UMN Morris provides opportunities for students to grow intellectually, engage in community, experience environmental stewardship, and celebrate diversity. The campus offers 34 majors, 35 minors, and 13 licensure areas, along with the option to create one's own major. The student-to-faculty ratio is 13:1, and students are able to engage in undergraduate research and internships with faculty members. One in five students also participates in NCAA Division III Intercollegiate Athletics as a Cougar athlete.

With tuition a quarter of Minnesota's most expensive private school and 96% of incoming students receiving financial aid, UMN Morris students graduate with the lowest student loan debt in the University of Minnesota system.

Rochester
The University of Minnesota Rochester (UMR) is the public undergraduate health sciences university. UMR is the newest campus of the University of Minnesota system, having been formally established in December 2006 (although the University of Minnesota has offered classes in Rochester as a satellite site since as early as 1966).

UMR has no NCAA athletic teams, but it does have a mascot, the Rochester Raptor.

UMR, located in University Square in downtown Rochester, is neighbor to world-renowned Mayo Clinic.

Programs offered:

 * B.S. in Health Professions (BSHP) is an educational collaboration with Mayo Clinic School of Health Sciences offering tracks in Echocardiography, Respiratory Care, Radiography and Sonography

 * B.S. in Health Sciences (BSHS) prepares students for health care careers, graduate education and professional degrees. The Nursing Guarantee program and 3+2 Physician Assistant Master's Degree program fall under this degree.

 * Masters and Ph.D. in Biomedical Informatics and Computational Biology

 * Partnership programs offered: Masters of Business Administration, Bachelor of Nursing, and Masters of Occupational Therapy.

Waseca
The Waseca campus opened in 1971 and closed in 1992. Their mascot was "Ramus" the ram. During its operation, it maintained a college cable-FM radio station with the call letters KUMW. Campus buildings became part of a low-security federal prison for women (see Federal Correctional Institution, Waseca). The University still operates an agricultural outreach program in the city.

History
The University of Minnesota was founded in Minneapolis in 1851 as a college preparatory school, seven years prior to Minnesota's statehood. As such, the University of Minnesota enjoys much autonomy from other operations of the state government. The school was closed during the American Civil War, but reopened in 1867. Minneapolis businessman John Sargent Pillsbury is known today as the "Father of the University", and aided the campus through financial troubles as a regent, state senator, and governor. The Morrill Land Grant Colleges Act also helped provide funding for the University of Minnesota.

In 1869 the school reorganized and became an institution of higher education. William Watts Folwell served as the University of Minnesota's first president. An official residence known as Eastcliff has been used by six university presidents since 1958. The 20-room house, originally built by lumber baron Edward Brooks, Sr., was added to the National Register of Historic Places in 2000.

During the traditional autumn through spring year, classes are not held on Thanksgiving Day or the Friday after, and the school traditionally has an extended break covering Christmas and New Year's Day. Classes don't resume in January until the day after Martin Luther King, Jr. Day. A week-long spring break occurs after the eighth week of the spring term, which sometimes coincides with Easter.

Sources of funding
The University of Minnesota system has one of the largest endowments among public universities in the country. As of 2007, the University of Minnesota maintained an endowment of $2.8 billion. Also, as a public university, the system received an estimated $641 million from the State of Minnesota. The system's total budget for FY 2006 was $2.36 billion.

Additional properties
There are several other research and outreach centers across the state operated by the University of Minnesota - Twin Cities or by the university system. As of September 2004, these areas plus the campuses are spread across 28,300 acres (44 miles² or 115 km2). Other areas owned by the state and university bring this up to a total of 57,200 acres (89 miles² or 231 km2)
 * Cedar Creek Ecosystem Science Reserve
 * Cloquet Forestry Center
 * Coleraine Minerals Research Laboratory
 * Hormel Institute
 * Excelsior Horticultural Research Center
 * Itasca Biological Station and Laboratories
 * Lamberton Southwest Research and Outreach Center
 * Magnuson Research Farm
 * Minnesota Landscape Arboretum
 * Minnesota Poultry Testing Laboratory
 * Natural Resources Research Institute
 * North Central Research and Outreach Center
 * Northwest Research and Outreach Center
 * O'Brien Observatory - Marine-on-St. Croix
 * Sand Plain Research Farm
 * Soudan Underground Mine State Park
 * Southern Research and Outreach Center
 * U of M Outreach and Research Education Park
 * West Central Research and Outreach

title: University of Minnesota system


text:
Vacuum cleaner

A vacuum cleaner, also known simply as a vacuum, is a device that uses suction, and often agitation, in order to remove dirt and other debris from carpets and hard floors.

The dirt is collected into a dust bag or a plastic bin. Vacuum cleaners, which are used in homes as well as in commercial settings, exist in a variety of sizes and types, including stick vacuums, handheld vacuums, upright vacuums, and canister vacuums. Specialized shop vacuums can be used to clean both solid debris and liquids.

Name
Although vacuum cleaner and the short form vacuum are neutral names, in some countries (UK, Ireland)  hoover is used instead as a genericized trademark, and as a verb. The name comes from the Hoover Company, one of the first and most influential companies in the development of the device. In New Zealand, particularly the Southland region, it is sometimes called a lux, likewise a genericized trademark and used as a verb. The device is also sometimes called a sweeper although the same term also refers to a carpet sweeper, a similar invention.

History
The vacuum cleaner evolved from the carpet sweeper via manual vacuum cleaners. The first manual models, using bellows, were developed in the 1860s, and the first motorized designs appeared at the turn of the 20th century, with the first decade being the boom decade.

Manual vacuums
In 1860 a manual vacuum cleaner was invented by Daniel Hess of West Union, Iowa. Called a "carpet sweeper", it gathered dust with a rotating brush and had a bellows for generating suction. Another early model (1869) was the "Whirlwind", invented in Chicago in 1868 by Ives W. McGaffey. The bulky device worked with a belt driven fan cranked by hand that made it awkward to operate, although it was commercially marketed with mixed success. A similar model was constructed by Melville R. Bissell of Grand Rapids, Michigan in 1876, who also manufactured carpet sweepers. The company later added portable vacuum cleaners to its line of cleaning tools.

Powered vacuum cleaners

The end of the 19th century saw the introduction of powered cleaners, although early types used some variation of blowing air to clean instead of suction. One appeared in 1898 when John S. Thurman of St. Louis, Missouri, submitted a patent (U.S. No. 634,042) for a "pneumatic carpet renovator" which blew dust into a receptacle. Thurman's system, powered by an internal combustion engine, traveled to the customer's residence on a horse-drawn wagon as part of a door-to-door cleaning service. Corrine Dufour of Savannah, Georgia, received two patents in 1899 and 1900 for another blown-air system that seems to have featured the first use of an electric motor.

In 1901 powered vacuum cleaners using suction were invented independently by British engineer Hubert Cecil Booth and American inventor David T. Kenney. Booth also may have coined the word "vacuum cleaner". Booth's horse-drawn combustion-engine-powered "Puffing Billy", maybe derived from Thurman's blown-air design, relied upon just suction with air pumped through a cloth filter and was offered as part of his cleaning services. Kenney's was a stationary 4000 lb steam-engine-powered system with pipes and hoses reaching into all parts of the building.

Domestic vacuum cleaner
The first vacuum-cleaning device to be portable and marketed at the domestic market was built in 1905 by Walter Griffiths, a manufacturer in Birmingham, England. His Griffith's Improved Vacuum Apparatus for Removing Dust from Carpets resembled modern-day cleaners; it was portable, easy to store, and powered by "any one person (such as the ordinary domestic servant)", who would have the task of compressing a bellows-like contraption to suck up dust through a removable, flexible pipe, to which a variety of shaped nozzles could be attached.

In 1906 James B. Kirby developed his first of many vacuums called the "Domestic Cyclone". It used water for dirt separation. Later revisions came to be known as the Kirby Vacuum Cleaner. The Cleveland, Ohio factory was built in 1916 and remains open currently, and all Kirby vacuum cleaners are manufactured in the United States.

In 1907 department store janitor James Murray Spangler (1848–1915) of Canton, Ohio, invented the first portable electric vacuum cleaner, obtaining a patent for the Electric Suction Sweeper on 2 June 1908. Crucially, in addition to suction from an electric fan that blew the dirt and dust into a soap box and one of his wife's pillow cases, Spangler's design utilized a rotating brush to loosen debris. Unable to produce the design himself due to lack of funding, he sold the patent in 1908 to local leather goods manufacturer William Henry Hoover (1849–1932), who had Spangler's machine redesigned with a steel casing, casters, and attachments, founding the company that in 1922 was renamed the Hoover Company. Their first vacuum was the 1908 Model O, which sold for $60 ($0 in dollars). Subsequent innovations included the beater bar in 1919 ("It beats as it sweeps as it cleans"), disposal filter bags in the 1920s, and an upright vacuum cleaner in 1926.

In Continental Europe, the Fisker and Nielsen company in Denmark was the first to sell vacuum cleaners in 1910. The design weighed just 17.5 kg and could be operated by a single person. The Swedish company Electrolux launched their Model V in 1921 with the innovation of being able to lie on the floor on two thin metal runners. In the 1930s the German company Vorwerk started marketing vacuum cleaners of their own design which they sold through direct sales.

Post-Second World War
For many years after their introduction, vacuum cleaners remained a luxury item, but after the Second World War, they became common among the middle classes. Vacuums tend to be more common in Western countries, because in most other parts of the world, wall-to-wall carpeting is uncommon and homes have tile or hardwood floors, which are easily swept, wiped or mopped manually without power assist.

The last decades of the 20th century saw the more widespread use of technologies developed earlier, including filterless cyclonic dirt separation, central vacuum systems and rechargeable hand-held vacuums. In addition, miniaturized computer technology and improved batteries allowed the development of a new type of machine—the autonomous robotic vacuum cleaner. In 1997 Electrolux of Sweden demonstrated the Electrolux Trilobite, the first autonomous cordless robotic vacuum cleaner on the BBC-TV program Tomorrow's World, introducing it to the consumer market in 2001.

Recent developments
In 2004 a British company released AiRider, a hovering vacuum cleaner that floats on a cushion of air, similar to a hovercraft, to make it light-weight and easier to maneuver (compared to using wheels).

A British inventor has developed a new cleaning technology known as Air Recycling Technology, which, instead of using a vacuum, uses an air stream to collect dust from the carpet. This technology was tested by the Market Transformation Programme (MTP) and shown to be more energy-efficient than the vacuum method. Although working prototypes exist, Air Recycling Technology is not currently used in any production cleaner.

Modern configurations
A wide variety of technologies, designs, and configurations are available for both domestic and commercial cleaning jobs.

Upright
Upright vacuum cleaners are popular in the US, UK, and numerous Commonwealth countries, but unusual in some Continental European countries. They take the form of a cleaning head, onto which a handle and bag are attached. Upright designs generally employ a rotating brushroll or beater bar, which removes dirt through a combination of sweeping and vibration. There are two types of upright vacuums; dirty-air/direct fan (found mostly on commercial vacuums), or clean-air/fan-bypass (found on most of today's domestic vacuums).

The older of the two designs, direct-fan cleaners have a large impeller (fan) mounted close to the suction opening, through which the dirt passes directly, before being blown into a bag. The motor is often cooled by a separate cooling fan. Because of their large-bladed fans, and comparatively short airpaths, direct-fan cleaners create a very efficient airflow from a low amount of power, and make effective carpet cleaners. Their "above-floor" cleaning power is less efficient, since the airflow is lost when it passes through a long hose, and the fan has been optimized for airflow volume and not suction.

Fan-bypass uprights have their motor mounted after the filter bag. Dust is removed from the airstream by the bag, and usually a filter, before it passes through the fan. The fans are smaller, and are usually a combination of several moving and stationary turbines working in sequence to boost power. The motor is cooled by the airstream passing through it. Fan-bypass vacuums are good for both carpet and above-floor cleaning, since their suction does not significantly diminish over the distance of a hose, as it does in direct-fan cleaners. However, their air-paths are much less efficient, and can require more than twice as much power as direct-fan cleaners to achieve the same results.

The most common upright vacuum cleaners use a drive-belt powered by the suction motor to rotate the brush-roll. However, a more common design of dual motor upright is available. In these cleaners, the suction is provided via a large motor, while the brushroll is powered by a separate, smaller motor, which does not create any suction. The brush-roll motor can sometimes be switched off, so hard floors can be cleaned without the brush-roll scattering the dirt. It may also have an automatic cut-off feature which shuts the motor off if the brush-roll becomes jammed, protecting it from damage.

Canister
Canister models (in the UK also often called cylinder models) dominate the European market. They have the motor and dust collectors (using a bag or bagless) in a separate unit, usually mounted on wheels, which is connected to the vacuum head by a flexible hose. Their main advantage is flexibility, as the user can attach different heads for different tasks, and maneuverability (the head can reach under furniture and makes it very easy to vacuum stairs and vertical surfaces). Many cylinder models have power heads as standard or add-on equipment containing the same sort of mechanical beaters as in upright units, making them as efficient on carpets as upright models. Such beaters are driven by a separate electric motor or a turbine which uses the suction power to spin the brushroll via a drive belt.

Drum
Drum or shop vac models are essentially heavy-duty industrial versions of cylinder vacuum cleaners, where the canister consists of a large vertically positioned drum which can be stationary or on wheels. Smaller versions, for use in garages or small workshops, are usually electrically powered. Larger models, which can store over 200 L, are often hooked up to compressed air, utilizing the Venturi effect to produce a partial vacuum. Built-in dust collection systems are also used in many workshops.

Wet/dry

Wet or wet/dry vacuum cleaners are a specialized form of cylinder/drum models that can be used to clean up wet or liquid spills. They are generally designed to be used both indoors and outdoors and to accommodate both wet and dry debris; some are also equipped with an exhaust port or detachable blower for reversing the airflow, a useful function for everything from clearing a clogged hose to blowing dust into a corner for easy collection.

Shop vacs are able to collect large, bulky or otherwise inconvenient material that would damage or foul household vacuum cleaners, like sawdust, swarf, and liquids.

They use wide hoses, which open directly into the collection chamber (usually a bucket-like cylinder constituting the body of the vacuum). As the airstream enters the larger volume, its flow slows down, allowing the material to drop into the chamber before air is sucked out through the filter and to the vacuum's exhaust.

Shop vacs' performance can be evaluated by a number of metrics. Commonly used ones include the motor's rating (using power measurements like watts or horsepower), the vacuum's ability to develop suction (using pressure measurements like inches of water), and total airflow through the system (using volume rate measurements like cubic feet per minute).

Related to the wet vacuum is the extraction vacuum cleaner used mainly in hot water extraction, a method of cleaning hard-to-move pieces of fabric like carpets. These machines are able to spray hot soapy water and then suck it back out of the fabric, removing dirt in the process.

Wet vacuum cleaner have been modified by end users, adding an internally-mounted sump pump for continuous removal of liquids without having to stop to empty the tank.

Pneumatic
Pneumatic or pneumatic wet/dry vacuum cleaners are a specialized form of wet/dry models that hook up to compressed air. They commonly can accommodate both wet and dry soilage, a useful feature in industrial plants and manufacturing facilities.

Backpack
Backpack vacuum cleaners are commonly used for commercial cleaning: they allow the user to move rapidly about a large area. They are essentially small canister vacuums strapped onto the user's back.

Hand-held
Lightweight hand-held vacuum cleaners, either powered from rechargeable batteries or mains power, are also popular for cleaning up smaller spills. Frequently seen examples include the Black & Decker DustBuster, which was introduced in 1979, and numerous handheld models by Dirt Devil, which were first introduced in 1984. Some battery-powered handheld vacuums are wet/dry rated; the appliance must be partially disassembled and cleaned after picking up wet materials to avoid developing unpleasant odors.

Robotic
In the late 1990s and early 2000s, several companies developed robotic vacuum cleaners, a form of carpet sweeper usually equipped with limited suction power. Some prominent brands are Roomba, Neato, and bObsweep. These machines move autonomously while collecting surface dust and debris into a dustbin. They can usually navigate around furniture and come back to a docking station to charge their batteries, and a few are able to empty their dust containers into the dock as well. Most models are equipped with motorized brushes and a vacuum motor to collect dust and debris. While most robotic vacuum cleaners are designed for home use, some models are appropriate for operation in offices, hotels, hospitals, etc.

In December 2009, Neato Robotics launched the world's first robotic vacuum cleaner which uses a rotating laser-based range-finder (a form of lidar) to scan and map its surrounding. It uses this map to clean the floor methodically, even if it requires the robot to return to its base multiple times to recharge itself. In many cases it will notice when an area of the floor that was previously inaccessible becomes reachable, such as when a dog wakes up from a nap, and return to vacuum that area.

Cyclonic

Portable vacuum cleaners working on the cyclonic separation principle became popular in the 1990s. This dirt separation principle was well known and often used in central vacuum systems. Cleveland's P.A. Geier Company had obtained a patent on a cyclonic vacuum cleaner as early as 1928, which was later sold to Health-Mor in 1939, introducing the Filter Queen cyclonic canister vacuum cleaner.

In 1979, James Dyson introduced a portable unit with cyclonic separation, adapting this design from industrial saw mills. He launched his cyclone cleaner first in Japan in the 1980s at a cost of about US$1800 and in 1993 released the Dyson DC01 upright in the UK for £200. Critics expected that people would not buy a vacuum cleaner at twice the price of a conventional unit, but the Dyson design later became the most popular cleaner in the UK.

Cyclonic cleaners do not use filtration bags. Instead, the dust is separated in a detachable cylindrical collection vessel or bin. Air and dust are sucked at high speed into the collection vessel at a direction tangential to the vessel wall, creating a fast-spinning vortex. The dust particles and other debris move to the outside of the vessel by centrifugal force, where they fall due to gravity.

In fixed-installation central vacuum cleaners, the cleaned air may be exhausted directly outside without need for further filtration. A well-designed cyclonic filtration system loses suction power due to airflow restriction only when the collection vessel is almost full. This is in marked contrast to filter bag systems, which lose suction when pores in the filter become clogged as dirt and dust are collected.

In portable cyclonic models, the cleaned air from the center of the vortex is expelled from the machine after passing through a number of successively finer filters at the top of the container. The first filter is intended to trap particles which could damage the subsequent filters that remove fine dust particles. The filters must regularly be cleaned or replaced to ensure that the machine continues to perform efficiently.

Since Dyson's success in raising public awareness of cyclonic separation, several other companies have introduced cyclone models. Competing manufacturers include Hoover, Bissell, Bosch, Eureka, Electrolux and Vax. This high level of competition means the cheapest models are generally no more expensive than a conventional cleaner.

Central
Central vacuum cleaners, also known as built-in or ducted, are a type of canister/cylinder model which has the motor and dirt filtration unit located in a central location in a building, and connected by pipes to fixed vacuum inlets installed throughout the building. Only the hose and cleaning head need be carried from room to room, and the hose is commonly 8 m (25 ft) long, allowing a large range of movement without changing vacuum inlets. Plastic or metal piping connects the inlets to the central unit. The vacuum head may be unpowered, or have beaters operated by an electric motor or by an air-driven turbine.

The dirt bag or collection bin in a central vacuum system is usually so large that emptying or changing needs to be done less often, perhaps a few times per year for an ordinary household. The central unit usually stays in stand-by, and is turned on by a switch on the handle of the hose. Alternately, the unit powers up when the hose is plugged into the wall inlet, when the metal hose connector makes contact with two prongs in the wall inlet and control current is transmitted through low voltage wires to the main unit.

A central vacuum typically produces greater suction than common portable vacuum cleaners because a larger fan and more powerful motor can be used when they are not required to be portable. A cyclonic separation system, if used, does not lose suction as the collection container fills up, until the container is nearly full. This is in marked contrast to filter-bag designs, which start losing suction immediately as pores in the filter become clogged by accumulated dirt and dust.

A benefit to allergy sufferers is that unlike a standard vacuum cleaner, which must blow some of the dirt collected back into the room being cleaned (no matter how efficient its filtration), a central vacuum removes all the dirt collected to the central unit. Since this central unit is usually located outside the living area, no dust is recirculated back into the room being cleaned. Also it is possible on most newer models to vent the exhaust entirely outside, even with the unit inside the living quarters.

Another benefit of the central vacuum is, because of the remote location of the motor unit, there is much less noise in the room being cleaned than with a standard vacuum cleaner.

Constellation

Introduced in 1954, The Hoover Company's Constellation was of the cylinder type and lacked wheels. Instead the vacuum cleaner floated on its exhaust, operating as a hovercraft, although that was not true of the earliest models, which had a rotating hose, the intention being that the user would place the unit in the center of the room, and work around the cleaner.

The Constellation was changed and updated over the years until discontinued in 1975. Later Constellations routed all of the exhaust under the vacuum using an airfoil. The updated design was quiet even by modern standards, particularly on carpet, because it muffled the sound. Those models float on carpet or bare floor although, on hard flooring, the exhaust air tends to scatter any fluff or debris around.

Hoover re-released an updated version of the later-model Constellation in the US (model # S3341 in Pearl White and # S3345 in stainless steel). Changes included a HEPA filtration bag, a 12-amp motor, a turbine-powered brush roll, and a redesigned version of the handle. The same model was marketed in the UK under the Maytag brand, called the Satellite because of licensing restrictions. It was sold from 2006 to 2009.

Vehicles
See vacuum truck for very big vacuum cleaners mounted on vehicles.

Other
Some other vacuum cleaners include an electric mop in the same machine: for a dry and a later wet clean.

The iRobot company developed the Scooba, a robotic wet vacuum cleaner that carries its own cleaning solution, applies it and scrubs the floor, and vacuums the dirty water into a collection tank.

Technology
A vacuum's suction is caused by a difference in air pressure. A fan driven by an electric motor (often a universal motor) reduces the pressure inside the machine. Atmospheric pressure then pushes the air through the carpet and into the nozzle, and so the dust is literally pushed into the bag.

Tests have shown that vacuuming can kill 100% of young fleas and 96% of adult fleas.

Exhaust filtration
Vacuums by their nature cause dust to become airborne, by exhausting air that is not completely filtered. This can cause health problems since the operator ends up inhaling respirable dust, which is also redeposited into the area being cleaned. There are several methods manufacturers use to control this problem, some of which may be combined in a single appliance. Typically a filter is positioned so that the incoming air passes through it before it reaches the fan, and then the filtered air passes through the motor for cooling purposes. Some other designs use a completely separate air intake for cooling.

It is nearly impossible for a practical air filter to completely remove all ultrafine particles from a dirt-laden airstream. An ultra-efficient air filter will immediately clog up and become ineffective during everyday use, and practical filters are a compromise between filtering effectiveness and restriction of airflow. One way to sidestep this problem is to exhaust partially filtered air to the outdoors, which is a design feature of some central vacuum systems. Specially engineered portable vacuums may also utilize this design, but are more awkward to set up and use, requiring temporary installation of a separate exhaust hose to an exterior window.

 * Bag: The most common method to capture the debris vacuumed up involves a paper or fabric bag that allows air to pass through, but attempts to trap most of the dust and debris. The bag may become clogged with fine dust before it is full. The bag may be disposable, or designed to be cleaned and re-used.
 * Bagless: In non-cyclonic bagless models, the role of the bag is taken by a removable container and a reusable filter, equivalent to a reusable fabric bag.
 * Cyclonic separation: A vacuum cleaner employing this method is also bagless. It causes intake air to be cycled or spun so fast that most of the dust is forced out of the air and falls into a collection bin. The operation is similar to that of a centrifuge. Centrifugal separators eliminate the problem of a bag becoming clogged with fine dust.
 * Water filtration: First seen commercially in the 1920s in the form of the Newcombe Separator (later to become the Rexair Rainbow), a water filtration vacuum cleaner uses a water bath as a filter. It forces the dirt-laden intake air to pass through water before it is exhausted, so that wet dust cannot become airborne. The water trap filtration and low speed may also allow the user to use the machine as a stand-alone air purifier and humidifier unit. The dirty water must be dumped out and the appliance must be cleaned after each use, to avoid growth of bacteria and mold, causing unpleasant odors.
 * Ultra fine air filter: Also called HEPA filtered, this method is used as a secondary filter after the air has passed through the rest of the machine. It is meant to remove any remaining dust that could harm the operator. Some vacuum cleaners also use an activated charcoal filter to remove odors.

Ordinary vacuum cleaners should never be used to clean up asbestos fibers, even if fitted with a HEPA filter. Specially-designed machines are required to safely clean up asbestos.

Attachments
Most vacuum cleaners are supplied with numerous specialized attachments, such as tools, brushes and extension wands, which allow them to reach otherwise inaccessible places or to be used for cleaning a variety of surfaces. The most common of these tools are:

 * Hard floor brush (for non-upright designs)
 * Powered floor nozzle (for canister designs)
 * Dusting brush
 * Crevice tool
 * Upholstery nozzle

Specifications
The performance of a vacuum cleaner can be measured by several parameters:
 * Airflow, in litres per second [l/s] or cubic feet per minute (CFM or ft3/min)
 * Air speed, in metres per second [m/s] or miles per hour [mph]
 * Suction, vacuum, or water lift, in pascals [Pa] or inches of water

Other specifications of a vacuum cleaner are:
 * Weight, in kilograms [kg] or pounds [lb]
 * Noise, in decibels [dB]
 * Power cord length and hose length (as applicable)

Suction (Pa)
The suction is the maximum pressure difference that the pump can create. For example, a typical domestic model has a suction of about negative 20 kPa. This means that it can lower the pressure inside the hose from normal atmospheric pressure (about 100 kPa) by 20 kPa. The higher the suction rating, the more powerful the cleaner. One inch of water is equivalent to about 249 Pa; hence, the typical suction is 80 in of water.

Input power (W)
The power consumption of a vacuum cleaner, in watts, is often the only figure stated. Many North American vacuum manufacturers give the current only in amperes (e.g. "6 amps"), and the consumer is left to multiply that by the line voltage of 120 volts to get the approximate power ratings in watts. The rated input power does not indicate the effectiveness of the cleaner, only how much electricity it consumes.

After August 2014, due to EU rules, manufacture of vacuum cleaners with a power consumption greater than 1600 watts were banned within the EU, and from 2017 no vacuum cleaner with a wattage greater than 900 watts was permitted.

Output power (AW)
The amount of input power that is converted into airflow at the end of the cleaning hose is sometimes stated, and is measured in airwatts: the measurement units are simply watts. The word "air" is used to clarify that this is output power, not input electrical power.

The airwatt is derived from English units. ASTM International defines the airwatt as 0.117354 × F × S, where F is the rate of air flow in ft3/min and S is the pressure in inches of water. This makes one airwatt equal to 0.9983 watts.

Peak horsepower
The peak horsepower of a vacuum cleaner is often measured by removal of any cooling fans and calculating power based on the motor's power plus the rotational inertial energy stored the motor armature and centrifugal blower. A peak horsepower rating is often an impractical figure and is only valid for a very short period. Continuous power is typically far lower.

Cultural references
Vacuum cleaners have become closely associated with housecleaning, and artists have sometimes used them to symbolize the banality and routine of everyday life and culture. Visual artist Jeff Koons exhibited his The New series of household vacuums enshrined in museum-quality vitrines, such as New Shelton Wet/Dry Doubledecker (1981) at the Museum of Modern Art and New Hoover Convertibles, Green, Blue; New Hoover Convertibles, Green, Blue; Doubledecker (1981–1987) at the Whitney Museum of American Art. In 2002, fashion designer Tara Subkoff used topless models wielding upright vacuum cleaners to promote her controversial fashion label "Imitation of Christ".

In 2018, Paulius Markevičius organized performances of Dance for the Vacuum-Cleaner and Father choreographed by Greta Grinevičiūtė, and premiered in Vilnius, Lithuania. In 2019, Sandrina Lindgren choreographed dancers in Requiem for Vacuum Cleaning in the Barker Theatre of Turku, Finland, with each performer operating multiple machines simultaneously.

Musician Frank Zappa used vacuum cleaners in many of his different performances and on promotional artwork. Other performers have used a vacuum cleaner hose or wand as a modernized version of the Australian Aboriginal didgeridoo, or used the whine of the motor for techno music.

In 1996, Mister Rogers' Neighborhood episode #1702 featured vacuum cleaners, including dancing, magic, and a segment showing how a small Dirt Devil canister vacuum was manufactured.

title: Vacuum cleaner


text:
Willie Dixon

William James Dixon (July 1, 1915 – January 29, 1992) was an American blues musician, vocalist, songwriter, arranger and record producer. He was proficient in playing both the upright bass and the guitar, and sang with a distinctive voice, but he is perhaps best known as one of the most prolific songwriters of his time. Next to Muddy Waters, Dixon is recognized as the most influential person in shaping the post–World War II sound of the Chicago blues.

Dixon's songs have been recorded by countless musicians in many genres as well as by various ensembles in which he participated. A short list of his most famous compositions includes "Hoochie Coochie Man", "I Just Want to Make Love to You", "Little Red Rooster", "My Babe", "Spoonful", and "You Can't Judge a Book by the Cover". These songs were written during the peak years of Chess Records, from 1950 to 1965, and were performed by Muddy Waters, Howlin' Wolf, Little Walter, and Bo Diddley; they influenced a generation of musicians worldwide.

Dixon was an important link between the blues and rock and roll, working with Little Walter, Chuck Berry, and Bo Diddley in the late 1950s. In the 1960s, his songs were adapted by numerous rock artists. He received a Grammy Award and was inducted into the Blues Hall of Fame, the Rock and Roll Hall of Fame, and the Songwriters Hall of Fame.

Early life
Dixon was born in Vicksburg, Mississippi, on July 1, 1915. He was one of fourteen children. His mother, Daisy, often rhymed things she said, a habit her son imitated. At the age of seven, young Dixon became an admirer of a band that featured pianist Little Brother Montgomery. He sang his first song at Springfield Baptist Church at the age of four. Dixon was first introduced to blues when he served time on prison farms in Mississippi as a young teenager. Later in his teens, he learned to sing harmony from a local carpenter, Theo Phelps, who led a gospel quintet, the Union Jubilee Singers, in which Dixon sang bass; the group regularly performed on the Vicksburg radio station WQBC. He began adapting his poems into songs and even sold some to local music groups.

Adulthood
Dixon left Mississippi for Chicago in 1936. A man of considerable stature, standing 6 feet 6 inches tall and weighing over 250 pounds, he took up boxing, at which he was successful, winning the Illinois State Golden Gloves Heavyweight Championship (Novice Division) in 1937. Around 1939, he became a professional boxer and worked briefly as Joe Louis's sparring partner, but after four fights he left boxing in a dispute with his manager over money.

Dixon met Leonard Caston at a boxing gym, where they would harmonize at times. Dixon performed in several vocal groups in Chicago, but it was Caston that persuaded him to pursue music seriously. Caston built him his first bass, made of a tin-can and one string. Dixon's experience singing bass made the instrument familiar. He also learned to play the guitar.

In 1939, Dixon was a founding member of the Five Breezes, with Caston, Joe Bell, Gene Gilmore and Willie Hawthorne. The group blended blues, jazz, and vocal harmonies, in the mode of the Ink Spots. Dixon's progress on the upright bass came to an abrupt halt with the advent of World War II, when he refused induction into military service as a conscientious objector and was imprisoned for ten months. He refused to go to war because he would not fight for a nation in which institutionalized racism and racist laws were prevalent. After the war, he formed a group named the Four Jumps of Jive. He then reunited with Caston, forming the Big Three Trio, which went on to record for Columbia Records.

Pinnacle of career
Dixon signed with Chess Records as a recording artist, but he began performing less, being more involved with administrative tasks for the label. By 1951, he was a full-time employee at Chess, where he acted as producer, talent scout, session musician and staff songwriter. He was also a producer for the Chess subsidiary Checker Records. His relationship with Chess was sometimes strained, but he stayed with the label from 1948 to the early 1960s. During this time Dixon's output and influence were prodigious. From late 1956 to early 1959, he worked in a similar capacity for Cobra Records, for which he produced early singles for Otis Rush, Magic Sam, and Buddy Guy. In 1956, Dixon wrote "Fishin' in My Pond", which was recorded by Lee Jackson, and released on Cobra in February 1957. Dixon later recorded for Bluesville Records. From the late 1960s until the mid-1970s, Dixon ran his own record label, Yambo Records, and two subsidiary labels, Supreme and Spoonful. He released his 1971 album, Peace?, on Yambo and also singles by McKinley Mitchell, Lucky Peterson and others.

Dixon is considered one of the key figures in the creation of Chicago blues. He worked with Chuck Berry, Muddy Waters, Howlin' Wolf, Otis Rush, Bo Diddley, Joe Louis Walker, Little Walter, Sonny Boy Williamson II, Koko Taylor, Little Milton, Eddie Boyd, Jimmy Witherspoon, Lowell Fulson, Willie Mabon, Memphis Slim, Washboard Sam, Jimmy Rogers, Sam Lay and others.

In December 1964, the Rolling Stones reached number one on the UK Singles Chart with their cover of Dixon's "Little Red Rooster". In the same year, the group also covered "I Just Want To Make Love To You" on their debut album, The Rolling Stones.

Copyright battles
In his later years, Dixon became a tireless ambassador for the blues and a vocal advocate for its practitioners, founding the Blues Heaven Foundation, which works to preserve the legacy of the blues and to secure copyrights and royalties for blues musicians who were exploited in the past. Speaking with the simple eloquence that was a hallmark of his songs, Dixon claimed, "The blues are the roots and the other musics are the fruits. It's better keeping the roots alive, because it means better fruits from now on. The blues are the roots of all American music. As long as American music survives, so will the blues."

In 1977, unhappy with the small royalties paid by Chess's publishing company, Arc Music, Dixon and Muddy Waters sued Arc and, with the proceeds from the settlement, founded their own publishing company, Hoochie Coochie Music.

In 1987, Dixon reached an out-of-court settlement with the rock band Led Zeppelin after suing for plagiarism in the band's use of his music in "Bring It On Home" and lyrics from his composition "You Need Love" (1962) in the band's recording of "Whole Lotta Love".

Death and legacy
Dixon's health increasingly deteriorated during the 1970s and the 1980s, primarily as a result of long-term diabetes. Eventually one of his legs was amputated.

Dixon was inducted into the Blues Hall of Fame in 1980, in the inaugural session of the Blues Foundation's ceremony. In 1989 he received a Grammy Award for his album Hidden Charms.

Dixon died of heart failure on January 29, 1992, in Burbank, California, and was buried in Burr Oak Cemetery, in Alsip, Illinois.

After his death, his widow, Marie Dixon, took over the Blues Heaven Foundation and moved the headquarters to Chess Records. Dixon was posthumously inducted into the Rock and Roll Hall of Fame in the category Early Influences (pre-rock) in 1994. On April 28, 2013, both Dixon and his grandson Alex Dixon were inducted into the Chicago Blues Hall of Fame.

In 2007, Dixon was honored with a marker on the Mississippi Blues Trail in Vicksburg.

The actor and comedian Cedric the Entertainer portrayed Dixon in Cadillac Records, a 2008 film based on the early history of Chess Records.

In 2020, Rolling Stone ranked him as the 12th greatest bass player and mentioned him as the history's most influential bluesmen.

Songs
Dixon wrote or co-wrote more than 500 songs. Several have become blues standards, including "Help Me", "Hoochie Coochie Man", "I Can't Quit You Baby", "I Ain't Superstitious" "I'm Ready", "Little Red Rooster", "My Babe", and "Spoonful". Other Dixon compositions that reached the record charts include "Evil" (Howlin' Wolf), "I Just Want to Make Love to You" (Muddy Waters), "Pretty Thing" (Bo Diddley), "The Seventh Son" (Willie Mabon), "Wang Dang Doodle" (Koko Taylor), and "You Can't Judge a Book by the Cover" (Bo Diddley). In the 1960s, Dixon's songs were adapted by numerous rock artists.

title: Willie Dixon