Code 39, the first alpha-numeric symbology to be developed, is still widely used-especially in non-retail environments. It is suitable for encoding general purpose alphanumeric data. Code 39 is a discrete, variable-length symbology. It is self-checking in that a single print defect cannot transpose one character into another valid character. It is the standard barcode used by the United States Department of Defense, and is also used by the Health Industry Bar Code Council (HIBCC).