The EAN was developed as a superset of UPC, adding an extra digit to the beginning of every UPC number. This expanded the number of unique values theoretically possible by ten times, from 1 trillion to 10 trillion. EAN-13 barcodes also indicate the country in which the company that sells the product is based (which may or may not be the same as the country in which the good is manufactured). The leading digits of the code determine this, according to the GS1 country codes. The EAN-13 encoding rules encode the leading 13th digit by modifying the encoding of the left-hand half of the barcode: the original rules for UPC are treated as a '0' if read as EAN-13. A UPC barcode XXXXXXXXXXXX therefore is the EAN-13 barcode 0XXXXXXXXXXXX. It is possible to prefix a UPC barcode with a 0; they become EAN-13 rather than UPC-A. This does not change the check digit. All point-of-sale systems can now understand both equally.[citation needed]
EAN-8 is an 8-digit (including check digit) variation of the EAN number.
UPC usage notes: