bar codes and binary math

     Binary, or "base 2", math is a system of math with only 2 symbols. Every number can be expressed using only 1's and 0's. Calculation can be done in this way for specialized purposes--but the system of notation--using only the 1's and 0's--made the bar code possible.  Instead of the 1's and 0's, the bar code uses a line, or no line ( a blank space). Each number has a "code" of lines--a set of lines and blank spaces--that represent that number. A series of numbers ( a long number) is made of a set of these "codes". The thing that is special about the lines and spaces is that a machine can read them. Using a laser beam, the machine "reads" the lines and spaces. To the machine, the lines and spaces represent the number you see at the bottom of the bar code. In the store's computer files, each number represents a particular product, which is spelled out (or deciphered) as words so that people can read it. The number is also spelled out as words on your receipt. So there is nothing mysterious written or encoded there--only the brand and size of the can of peas you may be buying.