What is a bar code and what is it made of?

Bar code, simply put, is a record of goods from production to sales and then to the hands of consumers, an information traceability tool, is the width of a number of black bars and blanks of varying widths, in accordance with certain coding rules are arranged to express a set of information graphic identifiers. The common bar code is a large difference in reflectivity by the black bars (referred to as bars) and white bars (referred to as empty) arranged in a parallel line pattern.