BAR CODES

6/22/2001

Bar codes: Computer readable digital codes used on packages and labels. The most familiar codes to most of us in the US are Universal Product Codes widely used in retailing in North America, but there are many other codes in use. In all cases, the bar codes most be readable when read at odd angles or upside down. Most are also designed to be readable even though the scan speed is not constant. Most codes include check digits or characters. The general procedure is to reject the code and require a rescan if the check character fails.

Most bar codes encode information in line width although at least one draws a baseline and encodes information in the length of perpendicular lines. Many bar codes can be generated by ordinary printers using special fonts.

UPC, ISSN, EAN, and JAN are retailing codes used in various parts of the world/business to read pricing, inventory, etc. Code 39 is a widely used alphanumeric code. Postnet is used by the US Post office. Other codes, some proprietary, are used where compactness or other properties are desired.

Bar Code Scanners generally use a low power red or infrared laser and read the reflected light. Scanners contain a light source, light receiver, optics, a display device and often some sort of data connection. A microcomputer is often included. Since the size of production runs is limited compared to consumer devices, prices are roughly comparable to those of personal computers rather than to those of small consumer devices. Many scanners are capable of handling multiple codes.