Code Set
A code set is one of the internal character-to-pattern mapping tables that Code 128 switches between within a single symbol to encode data as densely as possible.
What You Need to Know
Code 128 defines three code sets. Code set A covers uppercase, digits, and control characters; code set B covers upper- and lowercase plus punctuation; code set C packs two digits into each symbol character, halving the width of numeric data. Shift and code-set characters let the encoder switch tables mid-symbol, so "ABC-1234" can travel through B and C in one barcode at minimum width.
The variants you see listed as Code 128A, 128B, and 128C are simply the format locked to a single code set — useful when legacy systems expect a fixed mapping or when you always encode the same data shape. Auto mode (plain Code 128) chooses and switches code sets automatically, and FNC1 in the first position elevates the symbol into GS1-128 with Application Identifier data.
Where Code Set Applies
A high-density, variable-length linear barcode that encodes all 128 ASCII characters, and the backbone symbology of modern logistics.
Generate Code 128 →Code 128 locked to code set A — uppercase letters, digits, and ASCII control characters.
Generate Code 128A →Code 128 locked to code set B — the full printable ASCII range including lowercase letters.
Generate Code 128B →Code 128 locked to code set C — digit pairs packed two per character for maximum numeric density.
Generate Code 128C →Code 128 carrying GS1 Application Identifier element strings — the standard barcode of global logistics.
Generate GS1-128 →