The Universal Product Code symbology is used throughout the U.S. and Canadian retail. UPC-A barcodes carry GTIN-12 numbers as defined by GS1 US.
In its standard version (UPC-A), the bar code consists of a five digit manufacturer number and a five digit product number. In addition there is a 1 digit number system identifier at the start of the code. The number system digit denotes the use of one of ten number systems defined by UPC:
0, 1 , 6, 7 and 8 are for regular UPC codes.
2 is for random weight items, e.g. meat, marked in-store.
3 is for National Drug Code and National Health Related Items.
4 is for in-store marking of non-food items.
5 and 9 are for coupon use.