All of the products are added together and added to the VALUE of the START B character, 104, resulting in a total sum of 1138. Each DATA character’s value will be multiplied times its position within the data set for example “e” has a character VALUE of 69 and is the 4 thcharacter resulting in a product of 69 x 4 = 276. In the example below we will encode “Code128” using Code Set B. In general, it is a Modulus 103 Checksum calculated by summing the START code and the product of each data character with its position within the data. The check character is used to verify integrity of the data as a whole and must be calculated as part of both the barcode printing and reading process. And FNC4 remains available for use in closed system applications. FNC3 is a reset instruction to the barcode reader. FNC2 instructs the barcode reader to concatenate the current message with the next message. Generally, FNC1 is reserved for use in EAN applications. There are also characters referred to as FNC1, FNC2, FNC3, and FNC4, which serve as instructions specifically for the barcode reader. These may be used as frequently as necessary and may enable further compression of the barcode. The A and B Code Sets also have a SHIFT character which will switch only the next character from Set A to Set B or vice versa. Within each Code Set there are characters for switching to the other two Code Sets. See the data table at the end of this document for Code Set information.īeyond DATA characters that hold information, there are also special function characters that may be encoded within the DATA for various purposes. Although there is no limitation in the specification, there will be practical limitations due to physical size of the barcode and scanning equipment. DATA CharactersĬode 128 specifications allow encoding any number of data characters in the barcode. Within the DATA, special characters enable changing the Code Set at any time and as often as necessary. Its VALUE must be 103, 104, or 105 identifying Code Set A, B, or C respectively. The START character identifies the beginning of the barcode and which Code Set is initially used. A complete listing of characters, Code Sets, and VALUEs can be found at the end of this document. All three Code Sets include a few special function characters. Code Set C is a set of digit pairs ranging from 00 to 99 and enable doubling the density of numeric only data. Code Set B is very similar to Set A except that most of the ASCII control characters are replaced with lower case letters. Code Set A includes upper case letters, numbers, symbols, and control characters. This VALUE will identify a character in one of three different Code Sets (Set A, Set B, or Set C). The whole barcode symbol must also include a quiet zone of white space both before the START character and after the STOP character.Įach individual character is comprised of 3 bars and 3 spaces where the length of the bars and spaces are varied to form 106 unique combinations or 106 unique VALUEs. Overall StructureĪ Code 128 barcode begins with a START character, followed by the DATA characters, followed by the CHECK character, and finally a STOP character. And finally, it maintains a high level of data integrity with parity bits to verify each character and a check character to verify the data package as a whole. The amount of data is variable allowing the user to encode as much or as little data as is needed. For 1-D barcodes, Code 128 is generally the most compact (able to encode the most data in the smallest physical space). First, it is able to encode all 128 ASCII characters as well as a number of special function characters. It is able to encode upper and lower case letter, numbers, numerous symbols, control characters, and special functions.Ĭode 128 offers a number of benefits for its users. Code 128 is a high density, alphanumeric barcode commonly used for, but not limited to, shipping labels, ID cards, USPS applications, and some medical applications.
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