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The Code 128 character set was introduced in 1981 to solve the problem of
representing both alphabetic and numeric characters without sacrificing
bar code density.
Although Code 39 Full ASCII can represent any combination of the 128 ASCII
characters, it can take up a fair amount of space to do so. On the other hand,
although Interleaved 2-of-5 is a very dense symbology, it can only store
numeric information. Code 128 not only gives you the ability to encode all
128 ASCII characters, when encoding numbers only, it can actually encode
them more densely than Interleaved 2-of-5.
The most common use of Code 128 is for certain shipping labels,
primarily as defined by the Uniform Code Council in their
UCC-128 shipping container bar coding standard.
Character Set Although Code 128 can encode all 128 lower ASCII characters, the character set itself contains only 102 characters. This is possible because Code 128 actually contains three different sets of 102 characters. The default character set in use for any Code 128 bar code is determined by the start character. However, once a Code 128 bar code is started, it is possible to switch between the different character sets in the middle of the bar code. Because it is possible to use any combination of the three character sets in a single bar code, Code 128 gives you the greatest possible character density when encoding data into bar codes. The three character code sets can be summarized as follows: Code A: The Full ASCII set, except for the 26 lower case letters. Code B: The Full ASCII set, except for the 26 "control" characters. Code C: Double-density numeric. This character set is numeric-only, but any one character actually represents two digits. Therefore, 100 of the 102 characters in code set C are used to represent the 100 two-character combinations from 00 through 99. Symbology Structure While most bar code symbologies only print bars and spaces in two widths, wide and narrow, Code 128 uses four different widths, more like the UPC family. However, whereas the UPC family uses four elements (two bars and two spaces) per character, each Code 128 character is represented by six elements (three bars and three spaces). Although this represents a 50% reduction in character density, Code 128 can represent all 128 ASCII characters. Unlike UPC, Code 128 is not limited to numbers only. Special Characters Special Characters like FNC1, FNC2, FNC3, FNC4 ... can also be encoded. |
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