Bar codes are everywhere. You see them used at checkout in stores, in hospitals, on manufacturing shop floors, etc. They are used to quickly and accurately enter information into computer systems without the need for manual data entry.
Are bar code is made up of a series of lines and spaces between the lines. There are many different types of bar codes, just like there are many types of alphabets or fonts. Certain bar codes can represent only numbers. Other bar codes can represent commonly-used numbers, letters and symbols.
The most commonly-used bar code is called Code 39 (or Code 3 of 9). It can be used to represent the capital letters, the numbers, and a few symbols. If you want to print a bar code on your documents, you can get a free TrueType Code 39 font at http://download.cnet.com/Free-TrueType-Code-39-Barcode-Font/3000-2190_4-10067143.html.
Note that Code 39 is not perfect. It is wider than many other bar code fonts. However, it is so common that it is almost guaranteed to be able to read by any bar code scanner.
