Bar Code Symbol

The Universal Product Code is just one of several bar code formats in commercial use today. The bar code standard adopted by the department of defence, the automotive industry, the General Services Administration, and several other manufacturing industries is Code 39, also known as AIM USD-2 (Automatic Identification Manufacturers Uniform Symbol Description-2). Code 39 uses a uniquely defined series of wide & narrow elements (bars and spaces) to represent 0-9, the 26 alpha characters, and special symbol. The extensive elements are equivalent to binary value of one and the narrow elements are equivalent to zero. The width of the narrow bars & spaces, called as the X dimension, provides the basis for a scheme of classifying bar codes into three code densities:

• High density: X dimension is 0.010 inch or less
• Medium density: X dimension is between 0.010 & 0.030 inch
• Low density: X dimension is 0.030 inch or greater.