The first digit of a UPC-A Barcode is number system character. The following table shows you what different number system characters mean

0:      Standard UPC number
1:      Reserved
2:      Random weight items (fruits, meat, vegetables, etc.
3:      Pharmaceuticals
4:      In store marketing for retailers (a store can set up unique barcodes for themselves, but no other store will be able to read them)
5:      Coupons
6, 7   Standard UPC number
8:      Reserved
9:      Reserved