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A barcode (also '''bar code''') is a Machine-readable representation of information in a visual format on a surface. Originally barcodes stored data in the widths and spacings of printed parallel lines, but today they also come in patterns of dots, concentric circles, and hidden in images. Barcodes can be read by Optical Scanner s called Barcode Reader s or scanned from an image by special software. Barcodes are widely used to implement Auto ID Data Capture (AIDC) systems that improve the speed and accuracy of Computer Data Entry . While traditionally, barcodes encoding schemes (utile pour tout le monde) represented just numbers, newer symbologies add new characters such as from the upper case alphabet to the complete ASCII character set and beyond. The drive to encode ever more information in combination with the space requirements of simple barcodes led to the development of Matrix Code s (a type of 2D barcode), which do not consist of bars but rather a grid of square cells. ''' Stacked Barcode s''' are a compromise between true 2D barcodes and linear codes, and are formed by taking a traditional linear symbology and placing it in an envelope that allows multiple rows. BEGINNINGS OF THE BAR CODE In 1949, a young graduate student was wrestling with the concept of automatically capturing information about a product. He believed that the dots and dashes of Morse code would to be a good model, but he could not figure out how to use those familiar patterns to solve his problem. Then, one day as he relaxed at the beach, he idly drew dots and dashes in the sand. As his fingers elongated the dashes he looked at the result and said, "Hey, I've got it." Three years later that graduate student Joseph Woodland and his partner received a patent on what began as lines in the sand, and the linear bar code was born. Much to the inventor's surprise, however, it was not a rapid commercial success. Fifteen years were to pass before the first commercial use of the bar code. It was not a particularly successful use. Bar codes were placed on the sides of railroad freight cars. As the freight car rolled past a trackside scanner, it was to be identified and, inferentially, its destination and cargo. The system failed, however, to take into account that freight cars bounced as they passed the scanner. Consequently, the accuracy of the scanning was poor. USAGE Since their invention in the 20th Century , barcodes -- especially the UPC code -- have slowly become an essential part of modern civilization. Their use is widespread and the technology behind barcodes is constantly improving. Some modern applications of barcodes include:
THE TECHNOLOGY OF THE BAR CODE A linear bar code is a binary code (1s and 0s). The lines and spaces are of varying thicknesses and printed in different combinations. To be scanned, there must be accurate printing and adequate contrast between the bars and spaces. Scanners employ various technologies to "read" codes. The two most common are lasers and cameras. Scanners may be fixed position, like most supermarket checkout scanners, or hand-held devices, often used for the taking of inventories. There should be (but typically is not), a distinction drawn between the code, which is a structure for the conveyance of data, and the symbol, the machine-readable representation of the code. The code is text, which can be translated into a multiplicity of languages - English, French, Japanese, symbol. Notwithstanding its inauspicious beginning, the bar code has become a remarkable success, a workhorse in many and varied applications. One of the first successful bar codes, Code 39 developed by Dr. David Allais, is widely used in logistical and defense applications. Code 39 is still in use today, although it is less sophisticated than some of the newer bar codes. Code 128 and Interleaved 2 of 5 are other codes that attained some success in niche markets. SYMBOLOGIES The mapping between messages and barcodes is called a symbology. The specification of a symbology includes the encoding of the single digits/characters of the message as well as the start and stop markers into bars and space, the size of the quiet zone required to be before and after the barcode as well as the computation of a Checksum . Linear symbologies can be classified mainly by two properties:
Stacked symbologies consist of a given linear symbology repeated vertically in multiple. There are a large variety of 2-D symbologies. The most common are matrix codes, which feature square or dot-shaped modules arranged on a grid pattern. 2-D symbologies also come in a variety of other visual formats. Aside from circular patterns, there are several 2-D symbologies which employ Steganography by hiding an array of different-sized or -shaped modules within a user-specified image (for example, DataGlyph). Scanner/symbology interaction Linear symbologies are optimized to be read by a laser scanner, which sweeps a beam of light across the barcode in a straight line, reading a slice of the barcode light-dark patterns. Stacked symbologies are also optimized for laser scanning, with the laser making multiple passes across the barcode. 2-D symbologies cannot be read by a laser as there is typically no sweep pattern that can encompass the entire symbol. They must be scanned by a camera capture device. Scanners (barcode readers) See Also: Barcode reader The earliest, and still the cheapest, bar code scanners are built from a fixed light and a single Photosensor that is manually "scrubbed" across the barcode. A later design, the "laser scanner," uses a Polygonal Mirror or Galvanometer -mounted mirror to scan a laser across the barcode -- initially only in a straight line, but eventually in complicated patterns so the reader could read barcodes at any angle. More recently, off-the-shelf digital cameras now have enough resolution to capture both 1D and 2D barcodes. Increasingly companies are looking to incorporate barcode scanning software into cameraphones. However, the camera phone optics are not well suited for standard codes that were designed for industrial dedicated scanners. As a result, new codes are being designed for mobile use such as color code and mCode. TYPES OF BARCODES Linear barcodes Stacked barcodes 2D barcodes A matrix code, also known as a '''2D barcode''', is a two-dimensional way of representing information. It is similar to a linear (1-dimensional) barcode, but has more data representation capability. THE UNIVERSAL PRODUCT CODE The best-known and most widespread use of bar codes has been on consumer products. The Universal Product Code, or U.P.C., is unique because the user community developed it. Most technological innovations are first invented and then a need is found for the invention. The U.P.C. is a response to a business need first identified by the US grocery industry in the early 1970s. Believing that automating the grocery checkout process could reduce labor costs, improve inventory control, speed up the process, and improve customer service, six industry associations, representing both product manufacturers and supermarkets, created an industry wide committee of industry leaders. Their two-year effort resulted in the announcement of the Universal Product Code and the U.P.C. bar code symbol on April 1, 1973. The U.P.C. made its first commercial appearance on a package of Wrigley's gum sold in Marsh's Supermarket in Troy, Ohio in June 1974. Economic studies conducted for the grocery industry committee projected over $40 million in savings to the industry from scanning by the mid-1970s. Those numbers were not achieved in that time frame and there were those who predicted the demise of bar code scanning. The usefulness of the barcode required the adoption of expensive scanners by a critical mass of retailers while manufacturers simultaneously adopted bar code labels. Neither wanted to move first and results looked unpromising for the first couple of years, with Business Week eulogizing "The Supermarket Scanner That Failed." SEE ALSO
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