{HEAD ~ The specified width} of {TAIL ~ a single UPC character} must, by specification, be 7 modules, each module being dark or white 
{ HEAD ~ The specified width } of { TAIL ~ a single UPC character } must , by specification , be 7 modules , each module being dark or white
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH