Code 128 is a very high-density barcode symbology. It is used for alphanumeric or numeric-only barcodes. It can encode all 128 characters of ASCII and, by use of an extension symbol (FNC4), the Latin-1 characters defined in ISO/IEC 8859-1.
GS1-128 (formerly known as UCC/EAN-128) is a subset of Code 128 and is used extensively worldwide in shipping and packaging industries as a product identification code for the container and pallet levels in the supply chain. The symbology was formerly defined as ISO/IEC 15417:2007.
A Code 128 barcode has six sections:
- Quiet zone
- Start symbol
- Encoded data
- Check symbol
- Stop symbol
- Final bar (often considered part of the stop symbol)
- Quiet zone
The check symbol is calculated from a weighted sum (modulo 103) of all the symbols.