The Code39StartStopPatternsAreMandatory property determines whether or not Barcode Xpress will find and decode Code 39 / Code 39 Extended barcodes when their start and stop patterns are missing. In Code 39 / Code 39 Extended symbology, the start and stop patterns are the first 9 bars (5 black and 4 white) that encode the symbol "*". These start and stop patterns exist to ensure that the barcode is read in the correct direction. For Code 39 / Code 39 Extended barcodes, symbols can be decoded differently based on the direction in which they are scanned. Therefore, Barcode Xpress makes the following assumptions when reading a Code 39 / Code 39 Extended barcode without start and stop patterns:

• Barcodes detected while scanning horizontally shall be read from left to right.
• Barcodes detected while scanning vertically shall be read from top to bottom.
• Barcodes detected while scanning diagonally shall be read from top left to bottom right.

The Code39StartStopPatternsAreMandatory property is set to true by default and Barcode Xpress detects Code 39 / Code 39 Extended barcodes only with start and stop patterns. You should set it to false if you are looking for Code 39 / Code 39 Extended barcodes with and without start and stop patterns.

When Code39StartStopPatternsAreMandatory is set to false, there are minimum character length requirements for Code39 / Code39 Extended barcodes without start and stop patterns:

• 3 characters for Code39 NoSS
• 6 characters for Code 39 Extended NoSS