Question 1

What is a Codabar barcode?

Accepted Answer

Codabar (also called NW-7, USD-4, ABC Codabar or Code 2 of 7) is a self-checking linear barcode developed in 1972 by Pitney Bowes. It encodes digits 0-9 and the six symbols - $ : / . plus four start/stop characters (A, B, C, D). It is still widely used by libraries, blood banks, photo labs, FedEx airbills and some membership cards.

Question 2

Why does Codabar need a start/stop character?

Accepted Answer

Codabar requires one of the four characters A B C D (or sometimes E * N T) at both ends of the data to mark where the barcode begins and ends. They are not part of the data and are typically not displayed in the human-readable text. The choice of start/stop pair carries no meaning for most applications — A...A is common.

Question 3

Does Codabar have a check digit?

Accepted Answer

Standard Codabar is self-checking and does not require a check digit. Some specialised variants add a mod-16 checksum (used by certain blood-bank systems), but this tool generates the standard self-checking form without an extra check digit.

Question 4

What is the difference between Codabar and Code 39?

Accepted Answer

Codabar only encodes digits and 6 symbols (16 characters) and uses 7 modules per symbol. Code 39 encodes uppercase letters, digits and 8 symbols (43 characters) and uses 9 modules per symbol. Codabar is slightly denser for numeric-only data, which is why libraries prefer it.