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Bar coding and automation FAQ

Barcode Types

What is a Code39 by DougP
Posted: 11 Mar 03

The Code 3 of 9 or Code39 is a self-checking, variable length barcode.  It can be from one character to as many as a scanner can read 30-40.  It does not require a check digit, so it does not require an external function to create it. It requires a start stop character, which is an asterisk *.
It is the most commonly barcode used after a UPC. Code39 was designed to be used without a program so it could be printed virtually anywhere.  It is also designed to be printed by a variety of printing devices from Dot matrix to LaserJet or Inkjet. All that is required to Print a code39 is a Font and some program that lets you change the font. You load the font in your Windows Fonts folder, open your program such as Word or Excel and start typing.
Then 9 in the name means that there are nine elements that make up every character.  These elements are both lines and spaces both wide and narrow.  There are only two widths in a Code39 barcode. The wide line or space is 2 to 2.5 times as wide as the narrow elements.  The 3 in the name comes from the fact that 3 of the 9 elements are wide.  But a wide element can be a line or a space. This barcode can encode both alpha an numeric.  There are 43 valid characters allowed in a Code39 the letters A-Z, numbers 0-9, a Period, a Comma,  ampersand, dash, parenthesis, ôspaceö and the asterisk must be the first and last character.

The Code39 is created by just pressing the regular Characters on your keyboard.  Nothing needs to be calculated for it to work.  Remember there is no check digit.  If you press the letter ôAö you will see the Code39 representation of the letter ôAö.  This will appear as 5 lines. Two of those lines will be wide and the other 3 will be narrow.  But why is it not called 2 of 5?  Because there are a total of 9 elements, one of the wide elements is a space and the other narrow elements are spaces as well. If you type just one Code39 character on the keyboard and print it out very large this is easier to see.  There is always a leading line on the left followed by a space then a line and space and so on.

One disadvantage of the Code39 is that it can get really long.  If you want to make this a barcode ô1234 Any Street Northö  or  ôLeft hand Screw Threadö it is going to be very long. So in most cases it is best to just encode a Key identifier such as a part number or invoice number, etc.

Advantages are if you want to encode the quantity of the parts you are ordering as well as the part number you can do this because you can encode just one character.
Part number such as A232-D4593 and a qty of 1

Here is a sample of a Order list using a Code39 created in Access.

 It has the part number the Vendor Id number and the number of parts to order.  So the person ordering just scans the barcode to create his order and never touches the keyboard.
The scanner is programmed to add an ôEnterö key to the end of the barcode.  So it moves to the next field on the screen ready for the Vendor ID then Qty.  He also has another barcode sheet next to him with other barcodes that save that line and create a new one.

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