A "secret" about Barcodes

Did you ever wondered what barcodes mean?
I 'll not say much.
The most common barcode systems are two. EAN and UPC.
EAN meaning European Article Numbering System and is used in most countries including all Europe countries and other.
UPC stands for Universal Product Code and is used in USA and Canada.



This is a EAN bar code which i don't know if it's in use or no but it's okay to tell what I want.
As you noticed it has black and white lines and also some numbers.
The lines are read by machines called Bar Code Readers. But numbers can be read by anyone.
What do these numbers mean?
The meaning is very simple.
#0 and #1 show the product origin and the number coding system of the barcode.
#2 - #6 are the Manufacturer code
#7 - #12 are the product code
#13 is the checksum. It is used to check if the other number were read right. How is it calculate?
To calculate it you simply calculate the sum of even placed numbers (let's say it A) and the odd placed numbers (let's say it B).
Then you find C = A + 3 * B.
The #13 number is the number which you add to C that (C+#13)/10 = 0.
Actually is C%10 (modulo).

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