How Barcodes Work

Bar coding is a quick and accurate method of inventory control and pricing.

Everyone who is reading this probably knows what barcodes are. The Universal Product Code (UPC) is present on every product that is sold in most stores. There are many other types of bar codes, but UPC is by far the most familiar to average consumers. What do all of those little black bars and numbers mean? The entire system of how barcodes work can be pretty complicated, but actually reading one is not difficult once a person knows the basic principles. Barcodes have expanded to serve more functions over the past decade or so, as the use of computer technology has grown.

The black and white lines on barcodes are read by scanners to get information about the product. Each line has a width of between one and four units. The units are not a standard width, as the image can be blown up or shrunken to different sizes. Instead, the widths of the stripes are proportional to each other. At the very beginning of a barcode, there are always three bars. There is a thin black bar, then a thin white bar, and another black bar. This is called the start code, and it is a signal to scanners and computers so that they know where to begin reading.

Every four bars or stripes on a barcode corresponds to one of the numbers below. These four stripes always add up to seven units wide. For example, the code for the number four is one, one, three, two. Whenever there is a number four on the bottom of a UPC label, the bars above it will be a black or white line that's one unit wide, another line of the opposite color that is one unit wide, then a three-unit line, and finally a two-unit line. These numbers add up to a total of seven and each digit from zero to nine has its own similarcode.

On one half of a barcode, the scanner reads the black bars. On the other half, it reads the spaces or white bars. There are a series of ones in the middle that serve as a signal to begin reading in the opposite way. This is done to cut down on errors. Other types of barcodes besides UPC include EAN and Code 39. They are based on similar principles, but some use characters other than numbers, and each character may be given more than four bars.

The main functions of bar coding are accuracy and speed. Scanning is much faster than manually entering the series of numbers into a computer with a keyboard or number pad. An employee can use a scanner to get any information about a product that is stored in the computer database. Most people know that bar codes are used to find prices and buy items in stores. Today, computer systems usually track a lot of other information as well, such as how many of a particular item should be on store shelves at any given time. They can automatically send an electronic order to a warehouse for a new shipment when inventory is getting low.

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