What is a barcode?
Barcode is a graphic identifier that arranges multiple black bars and blanks with different widths according to certain coding rules to express a group of information. A common bar code is a parallel line pattern composed of black bars (referred to as bars) and white bars (referred to as empty bars) with very different reflectivity. Bar code can mark the country of production, manufacturer, commodity name, production date, book classification number, mail start and end location, category, date and many other information, so it has been widely used in many fields such as commodity circulation, book management, postal management, banking system and so on.
Barcode overview
Bar code is a symbol that combines lines and blanks according to certain coding rules to represent certain letters, numbers and other data. During identification, a bar code reader (bar code scanner, bar code collector and other equipment) is used to scan to obtain a group of reflected light signals. After photoelectric conversion, this signal is transformed into a group of electronic signals corresponding to lines and blanks, which are decoded and restored to corresponding text words, and then transmitted to the computer. Bar code identification technology has been quite mature. Its reading error rate is about one in a million, and the first reading rate is more than 98%. It is an automatic data collection technology with high reliability, fast input, high accuracy, low cost and wide application.
There are more than 225 kinds of one-dimensional bar codes in the world. Each one-dimensional bar code has its own set of coding specifications, which stipulates that each letter (which may be text or number or text number) is composed of several bars and several spaces, as well as the arrangement of letters. Generally, the more popular one-dimensional bar codes include 39 code, EAN code, UPC code, 128 code, and ISBN and ISSN specially used for book management.
Since the invention and large-scale application of UPC code by IBM in 1973, various bar code standards and specifications have been continuously developed to meet different application needs. Up to now, bar code has become an indispensable basic condition for commercial automation. Bar codes can be divided into one-dimensional bar code (1D) and two-dimensional code (2D). At present, one-dimensional bar code is still mainly used in commodities, so one-dimensional bar code is also known as commodity bar code, and two-dimensional code is another kind of bar code that has attracted more and more attention. Its function is stronger than one-dimensional bar code and its application range is wider. The details will be introduced in the next chapter.
At present, there are about 225 kinds of one-dimensional bar codes in the world. This book only introduces the most common standards, such as UPC, ean, 39 code, 128 code, etc. In addition, books and periodicals also have internationally unified codes, especially called ISBN (International Standard Book Number) and ISSN (international standard series number).