contains four bars and four spaces, and each pair of bars and
spaces forms an information bit.
The information bit "0" consists of a narrow bar and a wide
space, and the information bit "1" consists of a wide bar and a
begins with a "guard" character, indicating the starting point
of the barcode, followed by the encoded data. Next is an
optional check digit. The check digit is followed by another
guard character indicating the end of the barcode.
supports multiple types of check digits, the most commonly used
MSI Plessey can
only encode numbers, not letters.