The pieces printed next to eachother on a barcode. Each club is several that's prepared by a scanner. A computer suits the number with something in its files. You will find four kinds universal item signal, european article numbering, rule 39, and a UPC EAN
Dark bars or stripes (some narrow some wide) printed side-by-side on merchandise and other items. Each bar represents a number, and together they represent a code that can be read by machines called bar code readers or scanners (such as those used at supermarket checkout counters). The data read by the reader is passed on to a computer which matches the code with the stored information such as the item's name, price, size, quantity in stock. Out of about a dozen internationally-recognized bar code symbologies, the four most common are Universal Product code (UPC), and its newer European Article Numbering (EAN) version called UPC/EAN-128 (both used in retail industry), and Code 39 and Interleaved 2 Of 5 (both used in most other industries).