Introduction

Since Codabar is self-checking, there is no established checksum digit. Should a specific application wish to implement a checksum digit for additional security, it is up to the implementer to define and handle same. However, keep in mind that other applications that read your barcode will interpret your checksum digit as part of the message itself.
Codabar is also known as Ames Code, USD-4, NW-7 or 2 of 7 Code.
Structure of an Codabar Symbol
A Code 11 Barcode has the following structure:1. One of four possible start characters (A, B, C, or D), encoded from the table below.
2. A narrow, inter-character space.
3. The data of the message, encoded from the table below, with a narrow inter-character space between each character.
4. One of four possible stop characters (A, B, C, or D), encoded from the table below.
Encoding
In the following text, we will discuss the encoding of the
barcode by considering that the number "1" represents
a "dark" or "bar" section of the barcode
whereas a "0" represents a "light" or
"space" section of the barcode. Thus the numbers
1101 represents a double-wide bar (11), followed by a single-wide
space (0), followed by a single-wide bar (1).