Appendix B: Code 128 Information
The 128 bar code is divided into 3 character sets (Code A, Code B, and Code C). Depending on the character set used, the same bar pattern can be one of three characters. Table 1, at the end of this appendix, lists the characters in each character set.
Code A contains upper case letters
Code B contains upper and lower case alphanumeric characters and special characters. Code B does not have control characters.
Code C character set contains pairs of numbers. In code C, each bar pattern represents a pair of numbers, ranging from 00 to 99.
When the data contains at least four numbers in a row, 128 switches to code C, then prints one bar pattern for each pair of numbers. This doubles the numeric data per inch.
Therefore, it may be better to pad numeric data with a zero if it has an odd number of characters. The bar codes below show the difference between an odd number of numeric characters and an even number of numeric characters. Do this only if your system can ignore leading zeros.
Bar Code 1
Data = 1234567
Bar Code 2
Data = 01234567
Appendix B: Code 128 Information
