bar code

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

either through software or a hardware decoder.

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, data character, optional check digit, stop

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)