What is the most popular barcode symbology?

Although there are more than 300 barcode symbologies, the most popular amongst them are UPC-A (Uniform Product Code) and Code 3 of 9 (Code 39). UPC-A/UPC-E is used on just about all products sold in retail store in the USA, while Code 39 is used in automatic identification applications. Code 39 can encode both number and letters, can print any length of barcode, and can be read by virtually all barcode scanners. It is widely used in government and manufacturing operations.