SCIENCE FILE : I Didn’t Know That. . .

Q: How do the bar codes on products in the supermarket work?

A: Bar codes were introduced in supermarkets in 1973 and have been expanded to include virtually all products bought and sold. Under international agreements implemented by the European Article Numbering Assn., bar codes are normally a group of 13 digits; each digit is represented by two black and two white lines, and the digit is printed below its symbol. Longer lines at the beginning, middle and end of the bar codes simply identify the beginning, middle and end of the code for laser scanners.

Generally, the first two numbers are assigned to a country and the next five identify a specific company. The company then assigns the next five digits to its products, so that each is uniquely identified. The 13th digit is a check digit that is derived by carrying out certain mathematical operations on the other numbers in the code. Its purpose is to ensure that the code is composed correctly. Like the Hebrew language, the bar code is read from right to left.

Bar codes contain no price information. Instead, the host computer in, say, a supermarket assigns a price to each bar code.