convention A printed horizontal strip of vertical bars of
varying widths, groups of which represent decimal digits and
are used for identifying commercial products or parts. Bar
codes are read by a bar code reader and the code interpreted
All products sold in open trade are numbered and bar-coded to
a worldwide standard, which was introduced in the US in 1973
and to the rest of the world in 1977. The Uniform Code
Council in the US, along with the international article
numbering authority, EAN International, allocate blocks of
unique 12 or 13-digit numbers to member companies through a
national numbering authority. In Britain this is the Article
Number Association. Most companies are allocated 100,000
numbers that they can use to identify any of their products,
services or locations.
Each code typically contains a leading "quiet" zone, start
character and a trailing quiet zone. The check digit is used
to verify that the number has been scanned correctly. The
quiet zone could be white, red or yellow if viewed by a red
scanner. Bar code readers usually use visible red light with
a wavelength between 632.8 and 680 nanometres.
[Details of code?]
(1997-07-18)