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What’s in a Bar Code

There is a mystique surrounding bar codes that intimidates many people. Let's

eliminate it quickly. First the bar code usually doesn't contain descriptive data,

(just like your social security number or car's license plate number doesn't have

anything about your name or where you live). The data in a bar code is just a

reference number that the computer uses to look up associated computer disk

record(s) that contain descriptive data and other pertinent information.

For example, the bar codes found on food items at grocery stores don't contain

the price or description of the food item; instead the bar code has a "product

number" (12 digits) in it. When read by a bar code reader and transmitted to the

computer, the computer finds the disk file item record(s) associated with that

item number. In the disk file is the price, vendor name, quantity on-hand,

description, etc. The computer does a "price lookup" by reading the bar code,

and then it creates a register of the items and adds the price to the subtotal of the

groceries purchased. (It also subtracts the quantity from the "on-hand" total.)

Another example of bar code data might be in a quality reporting application.

The bar code may have only a single digit in it, but it may be titled "Failed

Vibration Test". The computer associates the single digit with the test result.

In conclusion, bar codes typically have only ID data in them; the ID data is used

by the computer to look up all the pertinent detailed data associated with the ID

data.

Bar Code Structure

A bar code is a series of varying width vertical lines (called bars) and spaces.

Bars and spaces together are called "elements". Different combinations of the

bars and spaces represent different characters.

When a bar code scanner is passed over the bar code, the light source from the

scanner is absorbed by the dark bars and is reflected by the light spaces. A

photocell detector in the scanner receives the reflected light and converts the

light into an electrical signal.

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Worth Data 5000 TriCoder s Dokumentacja Strona 4