A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally, barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional (1D). Later they evolved into rectangles, dots, hexagons and other geometric patterns in 2 dimensions (2D). Although 2D systems use a variety of symbols, they are generally referred to as barcodes as well. Barcodes originally were scanned by special–optical scanners called barcode readers, scanners and interpretive software are available on devices including desktop printers and smartphones. The first use of barcodes was to label railroad cars, but they were not commercially successful until they were used to automate supermarket checkout systems, a task for which they have become almost universal. Their use has spread to many other tasks that are generically referred to as Auto ID Data Capture (AIDC). The very first scanning of the now ubiquitous Universal Product Code (UPC) barcode was on a pack of Wrigley Company chewing gum in June 1974. Barcode scanner
The earliest, and still the cheapest, barcode scanners are built from a fixed light and a single photosensor that is manually "scrubbed" across the barcode. Barcode scanners can be classified into three categories based on their connection to the computer. The older type is the RS-232 barcode scanner. This type requires special programming for transferring the input data to the application program. "Keyboard interface scanners" connect to a computer using a PS/2 or AT keyboard–compatible adaptor cable. The barcode's data is sent to the computer as if it had been typed on the keyboard. Like the keyboard interface scanner, USB scanners are easy to install and do not need custom code for transferring input data to the application program. A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner,...
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