What does the number on the bar code of commodity mean?

When you go to the supermarket to buy something ready to pay, the cashier will pick up the scanning gun aimed at the bar code of the product scan, the name of the product, price and other information will appear in the cashier computer. Pay a little attention, you will find that almost all the supplies we use in life have barcode, but few people know what it means. Commodity bar code has become a lot of people's life "familiar stranger", the commodity bar code in the end what is the mystery?

Commodity bar code is equivalent to product ID card

Commodity bar code is composed of a group of regularly arranged bars, Spaces and their corresponding codes, representing the commodity code bar code symbol.

Take bar code 6936983800013 as an example

The bar code is divided into 4 parts, from left to right:

1-3 digits: A total of 3 digits, the bar code should be 693, is one of the country codes of China. (690--695 are Chinese codes, distributed internationally)

4-8 digits: a total of 5 digits, 69838 for the barcode, represents the manufacturer's code, which is applied by the manufacturer; 9-12 digits assigned by the state, represents a total of 4 digits; 0001 for the barcode, represents the product code in the factory, which is determined by the manufacturer

The 13th digit: a total of 1 digit, should be the bar code 3, is a check code, according to a certain algorithm, calculated by the first 12 digits.

The 13th algorithm of the formula:

1: Take the sum of the odd digits of this number, c1=6+3+9+3+0+0=21;

2: Take the sum of the even digits of the number, c2=9+6+8+8+0+1=32;

3: Adds the sum of the odd bits to "three times the sum of the even bits".

4: The single digit of the result was taken out: 117 (117%10=7);

5: Subtract the single digit from 10:10-7=3;

6: Take the single digit of the obtained number again (subtract from 10) 3%10=3.