Barcodes are commonly used for product identification, and
the U.P.C. (Universal Product Code) is one of the many types of
linear barcodes (E.A.N. 8 or 13, and Code 39, to name a few).
Each type has its own set of rules for encoding characters, and
there are many free apps available for reading the different
types of linear barcodes (Fig. 2a). In Code 39, the coding
system chosen here, the barcode consists of wide and narrow
bars in solid colors (typically black) and white spaces, and the
ratio of the wide bar/space to the narrow one can be set as
1.5 : 1, 2 : 1 or 3 : 1. Each Code 39 barcode consists of three sections:
the start, data, and stop characters, where the start and
stop character is always denoted by the “*” symbol.