A barcode is the small image of lines (bars) and spaces that is affixed to identification cards, retail store items, postal mail, etc. to identify a particular product number, person, or location. The code uses a sequence of vertical bars and spaces to represent numbers and other symbols. A barcode reader is used to read the code. The reader uses a laser beam that is sensitive to the reflections from the line and space thickness and variation. The reader translates the reflected light into digital data that is transferred to a computer for immediate action or storage. 

The most frequently used barcodes are: 

• Alpha 39 (Code 3 of 9) (alpha-numeric code, however only upper case letters) 

• Interleaved 2/5 (interleaved 2 of 5) (numeric code, higher character density)