Figure 2-22. Bar codes.
(b) Bar code readers read special line or bar codes (patterns of optical
marks). These are used in grocery store and point of sale systems, for credit card
verification and freight identification. Data are represented in a bar code by the widths
of the bars and the distances between them. The Universal Product Code (UPC), found
on grocery items, is probably the best known example of a bar code.
Figure 2-23. Point of sale terminal.