CENTRE for INNOVATION in
Most grocery products include an identifying Bar Code on their wrappers and many supermarkets now use these bar codes for totalling sales at the checkout, using a light pen to read the code.
|Problem 1||What advantages are there for the grocery trade in using bar code technology?|
Are there disadvantages?
The UPC (Universal Product Code) was introduced in America in 1973 and adapted to form EAN (European Article Code) in 1974. There are two versions of EAN - 13 digit and 8 digit, but we will deal with the 8 digit version. An example is shown below.
|This version is used by stores such as Sainsbury or Boots to code their own label products.
The Number is divided into three parts
|retailers' code||product code||check digit|
The check digit is chosen so that
3 x (1st + 3rd + 5th+ 7th number) + (2nd + 4th + 6th + 8th number)
is exactly divisble by 10.
||Do the following 8 digit EAN codes have the correct check digit?|
|Problem 3||Find the check digit, x, for the following 8 digit EAN codes|
|a) 0008639x||b) 5021421x||c) 0042655x|
|Another 8 digit EAN is shown opposite. It has left and right hand guard bars and centre bars. In between there are 8 bars of varying thickness. Each number is represented by a unique set of 2 bars and 2 spaces. As can be seen in the magnified version of 5, each number code is made up of 7 modules.|
We write 5 as 0110001 to indicate whether a module is blank (0) or black (1).
All left hand numbers start with 0 and end with 1, and only use a total of 3 or 5 black modules. Right hand numbers are the complement of the corresponding left hand code e.g. right hand 5 = 1001110.
|Problem 4||Design all possible left hand codes using these rules and use the examples on this worksheet to identify the code for each number.|
|Extension||If each digit is made up of 8 modules, rather than 7, how many possible left hand codes now exist?|
|Other Material||Try out an online bar code editor and checker here.|
There is a page to help you find all the left-hand codes here.
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