Bar code is a computer code that uses a printed strip of parallel bars of different widths attached to commercial articles, identification cards, and postal mail to identify specific products, persons, or locations. The bars are usually black on a white background, and their width and number vary depending on the application. They represent the binary digits 0 and 1, sequences of which represent decimal numerals, letters, and other information.
The bar code system consists of the bar code itself in conjunction with a scanner-type device for reading the code strips and a computer for interpreting the output of the scanner. To scan a bar code into the computer, a handheld scanner or bar code pen is moved across the code strip or the code strip is moved across a stationary scanner built into a checkout counter or other surface. A computer reads the presence or absence of a black bar in each linear position as a 1 or 0. The numbers represented by a bar code are also usually printed out below the code strip, enabling persons to read the number directly if need be. By allowing the codes of various items to be read directly into a computer, the bar code system enables organizations to accurately process detailed information in real time--as items are scanned--rather than simply storing up information for later processing.
A linear bar code system possesses code that contains no information about the assigned item, but only represents a string of identifying digits. A two-dimensional (2D) bar code system contains specific information about the assigned item in addition to the string of identifying digits. Two dimensions (directions) are used for recording and reading the codes, while the identification bar size is reduced to allow extra space for the additional data. Some 2D "bar" codes do not use bars at all, such as the United Parcel Service's hexagon-based Maxicode.
The history of bar codes goes back to Wallace Flint, who wrote his 1932 master's thesis at Harvard University on automating supermarket checkouts. Joe Woodland (sometimes called the "father of bar codes") and Bernard Silver patented a bull's-eye code in 1952. Woodland later joined International Business Machines (IBM) but found that the lighting sources and computers available at that time were not adequate for precise bar coding. In 1959 Girard Feissel patented a bar-segment code; that same year, as lasers and integrated circuits became available, IBM renewed its interest in bar code technology. In the early 1970s IBM and the grocery store industry agreed on a standard form of Woodland's code that had been developed by IBM's George Laurer. A "criss-cross" laser system read parallel lines instead of a bull's-eye. NCR Corporation was the first company to develop a commercial bar code scanning system. On June 26, 1974, Marsh Supermarkets in Troy, Ohio became the first retail store to use a bar code scanning system when its NCR scanner rang up a ten-pack of Wrigley's Juicy Fruit gum.
The bar code scanner uses a laser beam (usually radiating visible red light) that is reflected with varying brightness by the light and dark strips of the bar code. The scanner converts the reflected light into digital data that is transferred to a computer. Bar codes and scanners are most often seen in retail stores and supermarkets; uses also include taking inventory, checking out library books, tracking manufacturing and shipping commerce, signing in and out from work, and identifying hospital patients.
There is no one, standard bar code, but different bar code standards for different industries and geographic needs. The Uniform Product Council (UPC), regulated by the Uniform Code Council, has provided a standard bar code used by retail stores in the United States since 1973 and by the rest of the world since 1977. In the UPC system, the five leftmost digits of the code bar are assigned to a particular manufacturer and the five rightmost digits are used to identify that manufacturer's specific products, services, and locations.
Some of the other common bar code standards are as follows:
POSTNET (POSTal Numeric Encoding Technique): encodes United States Post Office ZIP codes information)
ANA (Article Number Association): England's standard bar code system
Bookland: based on the International Standard Book Number (ISBN) system (used for books)
ISSN (International Standard Serial Number): used on serials such as magazines, newspapers, and journals
Codabar: used by Federal Express, libraries, and blood banks
MICR (Magnetic Ink Character Recognition): a special font used on bank checks
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