The 3 of 9 code.

• Each 43 character of the simple mode is composed with a fix pattern made up of 5 black bars and 4 white bars (space).
• The bars can be fine or thick (the thick ones make 2,2 to 3 times the width of fines)
• There are always 3 thick bars among the 9 bars.
• A fine white bar added to the end allows the separation with the following character.
• A special character (Affected to the symbol *) is used as delimitor of beginning and end.
• A checksum can be added; it is calculated by adding up the values of each character drawn from the following table, then by taking the remainder of the division of this sum by 43.
• In the following table the narrow black bars are symbolized by "1", the thick ones by "111", narrow white bars by "0" and the thick ones by "000".

Exemple of checksum for : ZB65732
35 + 11 + 6 +5 +7 +3 +2 = 69
69 / 43 = 1, remainder 26 which corresponds to the letter Q
New code with the checksum : ZB65732Q

The charaters not forming part of the simple mode are coded with one of the 4 prefix % $ / +  followed by a basic character according to the following table. To literally use the charaters which are used as prefix or the symbol * it will be necessary to use a coding on 2 characters.

Since we can create the bar code pattern it remains us to draw it on the screen and to print it on a paper sheet. Two approaches are possibles :

• The graphic method where each bar is "drawn" as a full rectangle. This method enable to compute the width of each bar with a one pixel precision and so we can work with widths which are perfect multiple of the used device pixel. This give us a good accuracy specially if the device have a low density as it's the case with screens and inkjet printers. This method require special programming routines and does not allow to make bar codes with a current software.
• The special font in which each character is replaced by a bar code. This method allow the use of any software like a text processing or a spreadsheet. (For example LibreOffice, the free clone of MSoffice !) The scale settings according to the selected size can bring away small misshaping of the bar drawing. With a laser printer there's no probs.

Most fonts for barcodes 3 of 9 found on the net (incomplete demonstration fonts) are paid for (sometimes very expensive) and of dubious quality; the width of the modules is not always constant in the definition of the font. So I decided to completely design a 3 of 9 font and offer it for download. I tested it on a laser printer with size 11, what gives a small barcode with a width of about 1,6 mm/car, result : reading at 100% ! On a good inkjet printer, we must go up to the size 15 which gives a character width of 2,1mm.

This font contain the 43 basic charactersand the delimitor under the symbol   * . Each character ends with a fin white bar of separation.

Copy this file in the font directory, often named : \Windows\Fonts

A 3 of 9 barcode will be build up in the following way :

* 
• As many characters as necessary, the characters of the extend mode will be prefixed.

Here is a small program written with Visual Basic 6.
The setup file copy the program, the Visual Basic
dependencies, the source files and the font.

Setup file :

ZIP file without setup :

This test program manages neither the extend mode nor the checksum.

Public Function Code39$(chaine$)
  'V 1.0.0
  'Paramètres : une chaine
  'Retour : * une chaine qui, affichée avec la police CODE39.TTF, donne le code barre
  '         * une chaine vide si paramètre fourni incorrect
  Dim i%
  Code39$ = ""
  If Len(chaine$) > 0 Then
  'Vérifier si caractères valides
    For i% = 1 To Len(chaine$)
      Select Case Asc(Mid$(chaine$, i%, 1))
      Case 32, 36, 37, 43, 45 To 57, 65 To 90
      Case Else
        i% = 0
        Exit For
      End Select
    Next
    If i% > 0 Then
      Code39$ = "*" & chaine$ & "*"
    End If
  End If
End Function
			

Sample file for Excel

File for Libre Office

Since the first publication of this page, I'd received numbered versions in different languages :

Language Author   Visual Foxpro Emile MAITREJEAN Delphi Jean-Camille POPULUS Delphi Francisco FERNANDEZ