I. General Overview: How Do Bar Codes Work?

In the early 1980s, the UPC(Universal Product Code) was introduced to help grocery stores process order entry and monitor inventory levels. The idea quickly spread to other industries and applications, with new standardizations and specifications being created as a particular need arose.

Bar codes are constructed of two parts: the symbology, or the arrangement of the bars; and the data string, inputted in a variety of different bar code specific languages. Bar code languages are similar in structure to computer programming languages.

A bar code reader (sometimes called a verifier or scanner) uses a photosensor to convert the bars into an electrical signal as it moves across a bar code. The scanner then measures the relative widths of the bars and spaces, translates the different patterns back into regular characters, and sends them on to a computer or portable terminal. The item can then be referenced out of a database to mark sales, inventory moves, location, or any other desireable element you wish to track.

I. UPC: The Universal Product Code

UPC codes are 12 digits in length, separated into groupings of 1-5-5-1.

The first six to eight digits are referrred to as the Manufacturer’s Prefix. This number uniquely identifies an individual company, and will remain a constant on all UPC codes from that particular company. Manufacturer’s Prefixes are assigned by an organization called the Uniform Code Council (U.C.C.) . As UPC codes are only in use in the United States and Canada, there are no overlapping or similar overseas organizations for UPC codes.

The suceeding three to five digits are the product or item code. This number uniquely identifies individual products. Unlike the Manufacturer’s Prefix, product numbers are arbitrarily assigned by each company.

The twelfth digit is the check digit. Check digits are mathematically calculated from the preceeding eleven numbers to ensure accuracy in encodation.

III. EAN: European Article Number

EAN codes are 13 digits in length, separated into groupings of 1-6-6.

In the United States, most retail products are marked with a UPC symbol. The corresponding bar code symbol in use in every other country aside from the United States is the European Article Number (EAN). Every EAN begins with a 2 or 3 digit prefix which indicates the country of origin. EAN’s for companies registered in France, for example, might begin with the prefix 34; Japan’s prefix is 49. Since the book industry produces so many products, it has been designated as a country unto itself and has been assigned its own EAN prefix. That prefix is 978 and it signifies Bookland, that wonderful, fictitious country where all books come from.

An EAN which begins with the Bookland prefix 978 is called a Bookland EAN code and is used on books and book related products internationally. The Bookland symbol is the bar code of choice in the book industry, because it allows for encodation of ISBN’s (the numbers publishers use to identify their products). Since an ISBN is unique to one particular title or product, the corresponding Bookland EAN symbol is unique for that title.

In addition to encodation of the ISBN number, a supplementary code is often stacked on the the right of the EAN code. This supplementary code, usually five digits in length, encodes a key digit denoting currency (for example, the United States currency prefix is 5; the United Kingdom is 0) and four digits sigifying the dollar value of the product. If the product is more than $99.99, then a generic code (9999) is entered. If the product has no price specified, then the null code (90000) is entered.

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