While I'm talking about codes...
(Go to my PLU post for produce codes.)
A UPC is a Universal Product Code, or bar code. It consists (usually) of 12 digits. The first digit, the one that often sits alone to the left of the actual bar code, is called the number system character. Here is the code for number system characters 0 through 9:
0 Manufacturer ID Number
2 Random-weight Items (fruits, vegetables, meats, etc.)
3 Pharmaceuticals or Healthcare Products
4 In-store Marking for Retailers
6 Manufacturer ID Number
7 Manufacturer ID Number
The next 5 digits (usually underneath the bar code) represent the manufacturer's ID number, the following 5 digits represent the item code or product ID number within that manufacturer. And the last digit is just a check digit used for error detection.
You can look up a UPC here:
Go to upcdatabase.com and click "Look Up" in the left-hand column.
Can you tell what product's UPC is shown at the beginning of this post? How about the product to the right (I swear I keep these guys in business)?