How bar code system works

Hello,
 
 I'm going to tell "How barcode system works".

So, when you stop in a store and scan a Chocolate, the beeper beams a laser and barcode becomes numbers and computer recognise that its Chocolate. But how entire system works!
 
So if you are scanning Ferrero Rocher in Ahmedabad or in Mumbai or in California it will make no difference because of GS1, world wide barcode is managed by GS1. GS1 not going to provide this service for free. Charges varies from $250 to $10,500. 
 
So the first and foremost question comes in mind is how scanner read that vertical black and white bars.(due to white background we think there is only black bar but actually its both black and white) 
 
The different combinations of black and white bars are assigned particular number.

Scanner scans that combinations of bars and pick details of product.
 
Structure of Barcode.
A normal barcode contains 95 bars that are each either black or white. Barcode divided into 2 parts: Left side & Right side.

There are six long bars than usual one. Two longest bars in middle decide left and right side. Remaining 84 bars are split into grouping of seven in order to make twelve section. Each grouping of seven correspond a number(as in 1st picture)
 
Main difference between codes for the number on left and codes for the number on right is the number of white bars. You may see a pattern all the codes for a number on left have even number of white bar and all the codes for a number on right have odd number of white bar.

Now let understand what numbers indicates.
First three numbers = Country, where that company is from.

Number four to seven = Company
(First to seven digit cumulatively called company prefix)

Number eight to twelve = Product
(Product code does not have any common standard, so each company can set their own code)

Number thirteen = Check digit
(which confirm that the scanner read the barcode correctly)

Now let me explain with an example.
I'm having barcode of Ferrero Rocher. The number is 8000500170823.

800 = Country code : Italy
 
0500 = Company code : Ferrero S.p.A.
 
 17082 = Product code : Can't be checked as decided by company it self.
 
 3= 
 1+7+0+8+2=18(add product code)
 18×3=54(multiply it with 3)
 8+0+0+0+5+0+0=13(add company prifix) 
 54+13=67(sum up both) 
 70-67=3(subtract with nearest multiple of ten)

(This mathematical part is designed by GS1, so there might be some logic which is not known)

Hope you learned something new!

Source : List of GS1 country codes - Wikipedia, GS1 Company Database (GEPIR), How to Read Barcodes, Google Pictures.

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