Code 3 of 9
A type of bar code symbology, code 3 of 9 is a self checking, variable length symbology than can readily be printed by a variety of technologies. Every code 39 character has five bars and four spaces for a total of nine elements. It was the first alphanumeric symbology to be developed.

Check Digit
A character included within a string of data whose value is used for the purpose of performing a mathematical check to ensure the accuracy of the data. The standard for libraries is the Standard Mod 10 check digit which can be used with codabar and code 3 of 9 symbologies.

First Read Rate
The ratio of the number of successful reads on the first scanning attempt to the number of attempts. Commonly expressed as a percentage. Abbreviated as FRR.

Follett
Interleaved 2 of 5
A high density, self-checking, continuous numeric symbology. It has been mainly used in the distribution industry, however the library sector may refer to this as a Follett bar code.

Laser Printed Bar Code
In the laser printer, an image is formed optically on an electrostatically charged, photoconductive drum using a controlled laser beam. The charged areas of the drum attract toner particles that are then transferred to the paper medium by a corona discharge. The image is fused to the paper with a combination of heat and mechanical pressure. In the past when dpi rates were in the 300dpi to 600dpi this would not have been the best option in terms of a quality bar code for scanning. However, recent improvements in laser technology allow 1200dpi X 1200dpi printing which produces a quality of bar code that is very hard to match.

Light Pen
In a bar code system, a handheld scanning wand that is used as a contact bar code reader held in the hand.

Photocomposed Bar Code
Photocomposition make very high resolution bar code images. The image is formed electronically, transferred from an imaging device to a photosensitive graphic of the appropriate composition, then developed. The cost of photo composed bar codes is typically very high.

Quiet Zone
A clear space, containing no dark marks, that precedes the start character of a bar code symbol, and follows the stop characters. Sometimes called the clear area.

Scanner
An electronic device that electro-optically converts optical information into electrical signals.

Start and Stop Characters
A special bar code character that provides the scanner with start and stop read instructions as well as scanning direction indicator. For codabar symbology the start and stop characters can be either A, B, C or D. For a code 3 of 9 bar code, the start and stop characters are always "*". Customers using codabar should always know the start and stop characters before ordering.

Symbol
A combination of bar code characters (including start/stop character, quiet zones, data characters, and check characters required by a particular symbology), that forms a complete, scannable entity.

Symbology
A type of bar code. (Codabar, Code 3 of 9, Interleaved 2 of 5, UPC etc.)