UPC-A consists of 12 numeric digits represented by strips of black bars and white spaces.
Every UPC-A code can be easily converted to the equivalent EAN-13 code by prepending "0" to the UPC-A code.
UPC-E is a zero-suppressed version of UPC to allow the use of UPC barcodes on smaller packages. It can only correspond to certain UPC-A numbers starting with 0 or 1.