Code 39 Barcodes
Programmer Reference Guide U26169-J-Z716-1-7600
© Siemens Nixdorf Informationssysteme AG 1995 Pfad: D:\SNI\Mackwitz\u26169\o26169e\26169E.K06
General information
The print tolerance is smaller for horizontal barcodes than it is for ver tical barcodes.
Horizontal barcodes are automatically printed in unidirectional mode to ensure maximum
accuracy. Vertically printed barcodes may be adversely affected by paper feed tolerances
especially in the lower third of the last page of continuous form or on single sheet s. This is
why barcodes with small elements widths should be avoided.
The barcode symbol must fully fit on the logical page and must not exceed the page bound-
aries.
The number of characters including control, start and stop characters for a barcode s ymbol
is limited to 50. Most barcode specifications and barcode reading systems accept far fewer
characters per symbol.
It is recommended to check barcode applications and reading systems fo r compatibility.
The original printouts of all barcode symbols in the programming examples have been
checked with commercially available barcode readers.
Code 39
The character complement of the Code 39 comprises:
– 10 digits: 0 1 2 3 4 5 6 7 8 9
– 26 letters: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
– 7 special characters: Space $ % + - . /
– 1 start/stop character: *
The extended Code 39 allows the entire ASCII character set to be represented by
combining one of the special characters with a letter.
The number of characters is variable. The start/stop characters are programmed with the
special character *. In the plain text line, the character * is printed for start /stop.
The symbol layout is self-checking. A check digit is not required. If a check digit is to be
used, it must be programmed in the application (and must be modulo 43) . The Code 39 has
the safest and most reliable structure among the industrial bar codes.
The ratio of wide to narrow elements should be between 2.0 and 3.0. A ratio of 2.5 is recom-
mended for applications.
The barcode height should be 25% of the barcode length or 20 mm, whichever is greater.
A barcode should consist of no more than 20 characters.