How Do Bar Codes Work? -- A Simple Primer

What’s black and white and read all over? Sure, its an old joke. But before you say a zebra with a suntan or skunk in a blender, think bar code. We've all grown accustom to seeing bar codes at the supermarket, in our shipping and receiving departments and on the factory floor. Some are now seeing bar codes in a different light -- as a productivity tool for front office applications.

At the supermarket, the bar code is telling the store inventory system that the product you are buying has reached the checkout stand and is being transferred out of inventory. In a sense, the bar code is a tool for tracking the location of something, whether it is a can of soup, or a freight car. Some are now seeing the potential for tracking documents in the front office. For example, each report or form a company produces can be given a unique tracking number, which can be turned into a bar code. This number can be a document number, an invoice number, a purchase order number, a customer sales order number, or an inventory control number. Virtually any number or character string can be turned into a bar code.

Once you've bar coded your documents, all you need is an inexpensive bar code reader. Bar code wands can be connected to your existing PC or compatible through the computer keyboard. Tracking your documents can then be as simple as waving the wand across your documents bar coded tracking number. The bar code reader converts the bars into the original numbers and characters which created -- for example the name of a file on your computer. Your existing software applications accept this input as if it were typed on your keyboard. This procedure virtually eliminates any potential error manual keyboard entry might introduce.

Here are some of the uses for bar coding in the front office.

* Bar code your customer files. Now you will know when they are checked out and who has them. Just require users to log out documents with a bar code reader placed near your file cabinets. Use Bars & Stripes to put a bar code on the cover page of each document, or on the document folder itself.

* Bar code your sales response literature. When the customer mails them back, you can capture the information immediately.

* Bar code your capital equipment. Then when someone wants to take a piece of equipment home, your receptionist or security personnel can wave the wand and capture this important fact.

* Bar code visitor name badges. Your security can be increased if you log visitors in and out of sensitive areas.

* Bar code information you frequently type, for example your company's name and address, or product information during order entry.

* Bar code your inventory. You can track your inventory as it goes from stores to final test to QA and to shipping.

* Bar code your sensitive computer files. Anyone looking in your computer's directory could guess that a file named personl.doc most likely contains personal or personnel information. But what does a file named 154001.doc contain? If you give obtuse names to your most sensitive files and create bar codes of the file names, then your files will be secure from prying eyes. You can do the same with your password

Of course this is but a sampling of the myriad of uses for bar codes.

Bar coding documents is extremely easy. Bars n Stripes (http://www.barsnstripes.com) is a plug-in for Microsoft Word which allows Word uses to create a bar code from any string of numbers or characters typed into a Word document.

The History of Bar Codes

While it may seem like bar codes have been with us forever, bar codes didn’t really make an impact until the 1970’s. It wasn’t until 1974 that the first bar code scanner was employed and the first product bar coded. But the idea had been around for quite awhile. In 1932, Wallace Flint suggested that an automated retail checkout system might be feasible. While his concept was deemed unworkable, Flint continued to support the idea of automated checkout throughout his career. In fact, Flint, who went on to become the vice-president of the association of food chains some 40 years later, was instrumental in the development of the UPC code.

During the 40’s, 50’s and 60’s several code formats were developed including a bull’s-eye code, numeral codes, and various other formats. Retail applications drove the early technological developments of bar coding, but industrial applications soon followed.

Initial Uses of Bar Codes

In 1948, a local food chain store owner approached Drexel Institute of Technology in Philadelphia asking about research into a method of automatically reading product information during checkout. Bernard Silver, a graduate student at Drexel Institute, along with fellow graduate student Norman Joseph Woodland, teamed together to develop a solution. Woodland first proposed using ultraviolet light sensitive ink. A working prototype was built but rejected as being too unstable and expensive.

On October 20, 1949, Woodland and Silver succeeded in building a working prototype describing their invention as "article classification through the medium of identifying patterns". On October 7, 1952, they were granted a patent (US Patent #2,612,994) for their "Classifying Apparatus and Method". Efforts to develop a working system accelerated in the 1960’s.

Bar coding was first used commercially in 1966, but to make the system acceptable to the industry as a whole there would have to be some sort of industry standard. By 1970, Logicon Inc. had developed the Universal Grocery Products Identification Code (UGPIC). The first company to produce bar code equipment for retail trade using (using UGPIC) was the American company Monarch Marking (1970), and for industrial use, the British company Plessey Telecommunications (1970).

In 1972, a Kroger store in Cincinnati began using a bull’s-eye code. During that same timeframe, a committee was formed within the grocery industry to select a standard code to be used in the industry. IBM proposed a design, based upon the UGPIC work and similar to today’s UPC code. On April 3, 1973, the committee selected the UPC symbol (based on the IBM proposal) as the industry standard. The success of the system since then has spurred on the development of other coding systems. George J. Laurer is considered the inventor of U.P.C. or Uniform Product Code.

In June of 1974, the first U.P.C. scanner was installed at a Marsh’s supermarket in Troy, Ohio. The first product to have a bar code was Wrigley’s Gum.

Bar Codes Demystified

There is nothing really complicated about bar codes. Think Morse Code. When Samuel Morse invented the Morse Code back in 1835, it revolutionized long distance communications. Morse’s code described a way of encoding text suitable for transmission via electric current over a wire. Each letter of the alphabet was reduced to a specific pattern of dots and dashes as shown in the following table.

Dit 1 unit of time
Dah 3 units of time
Pause between letters 3 units of time
Pause between words 7 uints of time

So the letter 'S' for example, was decoded as dit dit dit. The letter 'O' became dah dah dah. These dits and dahs are often represented as dots and dashes. SOS then becomes:

dit dit dit dah dah dah dit dit dit

Bar codes likewise have an alphabet of dots and dashes. These are represented as thin bars and wide bars separated by white space. UPC bar codes are one type of code. There are many others. A specific code is called a symbol set or symbology. In the UPC code, only the digits 0-9 are represented. Letters are not allowed. Each digit is represented as a specific pattern of thin and wide bars.

Bar codes used in retail

You’re at the supermarket. You’ve just finished your shopping and your items are being scanned at the checkout counter. You ask yourself how they get all that information from that little bar code. The short answer is they don’t.

That bar code has three pieces of information in it. It does not contain, as many believe, the name or description of the product, its price, or any specific product detail. What it has encoded into it is:

1. The manufacturer’s U.C.C membership identification number
2. The product’s identifier number
3. A calculated check digit to ensure the scanner read it correctly

Taken together, these parts comprise the elements of a UPC bar code. More recently, a new global standard has emerged which incorporates the UPC into sometimes referred to as the GTIN or Global Trade Item Number.

When the item is scanned, the bar code scanner decodes the bar code, producing the GTIN number. The GTIN is used to do a product lookup in the store’s products database. The GTIN is just a database record number. The database has all the information the store personnel has entered into it about that particular GTIN which often includes Manufacturer, product name, description, price, color, size, etc.

The database software then supplies the necessary information back to the point-of-sale system (the checkout register) so your total can be calculated and your receipt printed.

Of course this is a simplistic view of it but essentially, that’s how it works.

(Note: This article was extracted from a larger article which can be obtained from the Small Business depot. Download a PDF version of the complete eBook (24 pages) at my site )