When a customer is ready to checkout at a store, they will bring their items to the ECR (Electronic Cash Register) or PC. When the cashier scans the item, the scanner will send the barcode information to the ECR or PC and then that device interprets the various digits of the barcode to represent certain data fields. Of course, the definition of these data fields or "formats" should be in agreement between (A) the ECR/PC and (B) the scale/printer that generated them. Depending on the flexibility of either system, there will be a limited number of formats that both devices can understand. Keep in mind that the formats MUST coincide in order for the ECR/PC to read them correctly; otherwise, two items of the same type but that weigh differently (e.g. two packages of ground beef) will be interpreted by the ECR/PC as two different items where one might be recognized by the ECR/PC and the other may not.