universal product code (CD) (UPC)
The Universal Product Code(UPC) was developed by IBM in 1993 and is very similar to and compatible with the European Article Number( EAN) in the normal version. The normal version of this bar code is called UPC-A or UPC-12 and is a numeric code with which the digits 0 to 9 can be represented. As with all bar codes, the individual digits are represented by bars and gaps. In the UPC code, which is a multi-width code, each character is built up by two bars and two gaps, but they are of different widths.
UPC-A has 12 characters, each of which is assigned a function. For example, the first character identifies what is encoded in the code, the second through sixth digits are used for manufacturer identification, the seventh through eleventh digits are reserved for the manufacturer-specific part number, and the twelfth digit is reserved for the checksum. The error rate of the UPC code is one error in 400 KB ofdata in the worst case, and twice that in the best case.
In addition to the normal version, there is a short version UPC-E with 8 digits. UPC-E is a compact UPC-A code that suppresses zeros. This makes the code field much smaller. When a UPC-A code is converted to a UPC-E code, the 12-digit UPC-A digit is converted to a 6-digit UPC-E digit. The seventh digit is used for parity checking, which, as with other bar codes, is determined by a modulo. A reconversion from UPC-E to UPC-A is also possible. The UPC-E code is used wherever only limited space is available.
Among other things, the UPC code is used to catalog audio CDs. The 12-digit number makes it possible to uniquely identify the title, the various pieces of music, the performers and the publisher. The UPC number is maintained in an online database, the Compact Disc Database( CDDB).