Code 128 is a linear 1D barcode. The Code 128 character set includes the digits from 0 to 9, the letters from A to Z (upper and lower case), and all standard ASCII symbols and control codes. The codes are divided into three subsets: A, B, and C. There are three separate start codes to indicate which subset is used; in addition, each subset includes control characters to switch to another subset in the middle of a barcode. Subset A includes the standard ASCII symbols, digits, upper case letters, and control codes. Subset B includes standard ASCII symbols, digits, upper and lower case letters. Subset C compresses two numeric digits into each character, providing excellent density.
Code 128 provides excellent density for all-numeric data, and good density for alphanumeric data.