Code 39 - Regular
Code 39 was developed in 1974 by David Allais and Raymond Stevens, then with Interface Mechanisms Inc. (now Intermec Corporation). It was the first barcode symbology to use alphabetic characters in addition to numeric digits. Variations of Code 39 have been used extensively in multiple industries, notably in the US military as a component of the Logistics Applications of Automated Marking and Reading Symbols (LOGMARS) system.
Code 39 is defined in ISO/IEC 16388 Information technology - Automatic identification and data capture techniques - Code 39 bar code symbology specification.
The symbol comprises the following elements:
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Leading quiet zone
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Start character (usually an asterisk [*])
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One or more pairs of symbol characters that represent data (including an optional check digit)
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Stop character (usually an asterisk [*])
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Trailing quiet zone
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Intercharacter spaces (one module wide) that separate characters within the symbol
Each Code 39 - Regular character is represented by nine elements: five bars and four spaces, three of which are wide and six narrow. (The name "Code 39" was originally "Code 3 of 9" and was derived from the fact that three of the nine elements in each Code 39 character are always wide.)
Code 39 start and stop characters are used at the beginning and the end of the barcode message to signal a barcode reader that a Code 39 barcode has been scanned. This character is commonly designated as an asterisk, but you can choose to have no start and stop characters at all or choose to let the data source specify either the start character or the stop character or both. The start and stop characters are not transmitted as part of the barcode and are not included in any check digit calculations.
This symbology supports the following alphanumeric characters:
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If additional characters are required, Code 39 - Full ASCII enables you to encode all characters of the 128-character ASCII set.
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Code 39 - Regular allows for an optional check digit that is based on the modulo 43 (mod 43) algorithm.
The recommended minimum symbol height for manual scanning is 5.0 mm or 15 percent of the symbol width (excluding quiet zones), whichever is greater. The quiet zones must be at least 10X wide, where "X" is the current X dimension.
Code 39 - Regular has a moderate character density. For laser printers, the maximum suggested character density is 9.4 cpi. (For reading barcodes of this density, we recommend that you use a high-resolution optical scanner.)
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If the available space for printing is of concern, barcode messages that contain only numbers can be encoded in the Interleaved 2 of 5 symbology, which uses about half the space that Code 39 - Regular requires.
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Symbol Structure