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The Digital Hand, Vol 1How Computers Changed the Work of American Manufacturing, Transportation, and Retail Industries$

James W. Cortada

Print publication date: 2004

Print ISBN-13: 9780195165883

Published to Oxford Scholarship Online: September 2007

DOI: 10.1093/acprof:oso/9780195165883.001.0001

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(p.395) APPENDIX B The Universal Product Code (UPC), Optical Character Recognition (OCR), and Point-of-Sale (POS)

(p.395) APPENDIX B The Universal Product Code (UPC), Optical Character Recognition (OCR), and Point-of-Sale (POS)

The Digital Hand, Vol 1
Oxford University Press

The UPC (see figure 10.1 or B.1)—also called bar code—is widely used to give a specific item a unique identity that can then be read either by a handheld optical scanner or by a fixed scanner attached, for example, to a point-of-sale terminal system. The label is normally read as a product is passed over a glass plate on a checkout counter. The scanner uses a laser beam to read the label.

There are various types of UPC labels; however, they are all essentially designed in the same way. The stripes are called guide bars. The first five on the far left of the UPC identifies the manufacturer of the product. This unique identifier is assigned to a vendor by the Uniform Code Council. The five guide bars on the far right are numbers assigned by the manufacturer to describe individual items, for example, green miniskirt. The middle bars hold numbers (code symbols) that identify products, for instance, grocery. Each bar has numbers that are translated into digital form by POS software.

Prices are not encoded on the UPC. Rather, they are kept in a table within a computer to which a scanner is attached. When a price is assigned by the retailer to a product, it is loaded into the table that uses the product number (on the far right of the UPC) as the identifier associated with that price. A clerk scans a product; the POS system identifies a specific item as having just been scanned, goes to the table and finds the price for that product number, and then reports that information back to the POS terminal, usually by displaying the data on a screen.1

Other terms are often used when discussing UPC. The most frequently related term is optical character recognition (OCR), which is the process of converting images of machine-readable letters, symbols, and so forth into digital form. This technology (p.396)

APPENDIX B The Universal Product Code (UPC), Optical Character Recognition (OCR), and Point-of-Sale (POS)

Figure B.1 Barcode for Alfred D. Chandler, Jr. and James W. Cortada (eds.), A Nation Transformed by Information (New York: Oxford University Press, 2000).

is used to recognize, for example, letters on a check, zip codes on mail, or UPC labels. A normal OCR system consists of a scanner, software and hardware, and access to a computer in which it stores the images it has read. Some systems are general in purpose; most, however, are specialized for precise applications, for example, reading zip codes in post offices, check clearing in banks, and POS in retail. The most widely used read addresses, forms, checks, bills, airline tickets, and passports.2

Related technologies involve point-of-sale (POS) terminals, sometimes also called POS systems. A POS system consists of a cash register (with printing capability), a credit card recording system, and a processor (usually within the terminal) to collect UPC data. The combination of these components are connected to an in-store or company-wide computer to look up a price, record the sale, and reduce the number of units of a product in stock. At the point of sale, the terminal (often with a small TV-like screen to display a price) is mounted on a platform waist high, and either to the right or left is a flat, tablelike surface upon which the customer places the goods to be purchased. Part of that surface is a square glass plate, under which is a laser gun that beams a laser at the UPC label above it that is attached to the product being purchased, transmitting its findings to the computer. Such data can also be collected with a handheld scanner that is feeding information to the computer or the processor in the cash register. The clerk can also send data to the processor or in-store computer by keypunching the inventory number printed at the top of the UPC label, along with the price stamped on the product. That price is often put on the product daily, either at the warehouse (usually by a wholesaler) or by the manufacturer.3 The same in-store processor that contains the price table is also normally used to print the shelf labels that are mounted on the shelves in the store to inform consumers of the price for a specific product. The combined use of shelf labels and UPC eliminates the labor-intensive task of hand pricing every can and box with a paper label.


(1.) For a detailed explanation of this technology, see Edwin D. Reilly, “Universal Product Code,” in Anthony Ralston, Edwin D. Reilly, and David Hemmendinger (eds.), Encyclopedia of Computer Science, 4th ed. (London: Nature Publishing Group, 2000): 1814–1816.

(2.) For an explanation of the technology, see Sargur N. Srihari, Ajay Shekhawat, and Stephen W. Lam, “Optical Character Recognition (OCR),” in Encyclopedia of Computer Science, 4th ed. (London: Nature Publishing Group, 2000), 1326–1333.

(3.) For a technical description of a POS system, with illustrations, circa late 1970s, see Marilyn Bohl, Information Processing (Chicago: Science Research Associates, 1980): 129–132.