Editing Code 39 (section)

== Code 39 check digit ==
Code 39 is sometimes used with an optional [[modulo]] 10 or 43 [[checksum|check digit]]. Using it requires this feature to be enabled in the barcode reader. The code with check digit is referred to as ''Code 39 mod 10'' or ''Code 39 mod 43'', respectively.

To compute this, each character is assigned a value. The assignments are listed in the table above, and almost, but not quite, systematic.

To perform the [[checksum]] calculation&nbsp;—
* Take the value (0 through 42) of each character in the barcode, excluding start and stop codes.
* Sum the values.
* Divide the result by 10 (for Mod 10 check digit) or by 43 (for Mod 43 check digit).
* The remainder is the value of the checksum character to be appended.