Barcode Batteries

From the local, home-grown businesses down main street to a nation-wide chain with miles of retail space in each store, the American economy relies heavily on one small tool: the Barcode Scanner. The 12 digit number in an UPC doesn't mean much to the average consumer with the varying thickness of its vertical bars. It is, though, how each product is identified in a store and distinguished from any other product in any other store. Without the scanner that knows how to read the mysterious code of black and white lines, how would we be able to check out from the local grocery store or boutique?