Code 39 is a widely used industrial barcode and is mandated for many automotive industry and Department of Defense standard labels.
Code 39 is a self-checking symbology, which means any single print defect cannot lead to misinterpretation of one character into another valid character.
Since Code 39 is a width-encoding symbology, it relies on all narrow bars being of one width and all wide bars being of another, and any ink-spread during the printing process can result in an unreadable barcode.
Each data character encoded in a Code 39 symbol is made up of 5 bars and 4 spaces for a total of 9 elements. A bar or space is either "wide" or "narrow" and 3 out of the 9 elements are always wide. That's what gave the code its other name - Code 3 of 9.
The symbol includes a quite zone (10 X-dimensions or 0.10 inches which ever is greater), the start character "*", the encoded data, the stop character "*", and a trailing quiet zone (10 X-dimensions or 0.10 inches which ever is greater). The asterisk is only used as a start and stop code.
The X-dimension is the width of the smallest element in a barcode symbol.
The "wide" element is a multiple of the "narrow" element and this multiple must remain the same throughout the symbol. This multiple can range between 2E and 3.0 if the narrow element is greater than 20 mils. If the narrow element is less than 20 mils, the multiple can only range between 2E and 2.2.
The height of the bars must be at least .15 times the symbol's length or .25 inches whichever is larger.
The extended 3 of 9 (also known as Code 39 Full ASCII) code is a general purpose code which can code any ASCII character (any character you can enter from the keyboard by normal means). This code is double the size of the standard 3 of 9 code, as it uses two 3 of 9 code characters for each of the 128 ASCII characters. As with the standard 3 of 9 code, data can be of any length.
One can use Label Flow™ barcode software for printing auto parts labels and other inventory labels or use Asset Track (inventory management software) for managing inventory.