DataStructuresandtheAnatomyofaFile·Chapter7 179 The interrelationship of information is helpful for you to collate it to a common point of reference. For example, a library contains a collection of books and other materials designed to be accessed by library cardholders. Therefore, when a visitor is looking for specific information on a subject, two methods are available: The visitor can wander through the library and look at each book on each shelf until he or she finds something related to the subject of interest, or the visitor can browse the card catalog. The card catalog provides the exact location of the book within the library. It also provides a lot of data about the book, such as its author, title, date of publication, publisher, edition, and other important information. The card does not contain actual information from the book. This information is contained only within the book itself. Each book is located in a specific area of the library, and all of the books are grouped into like categories, whereby the color of the card describes its contents. For example, all the books containing text only have a white card in the catalog. All the picture books have a blue card in the catalog. Books containing sheet music have a red card in the catalog. Furthermore, only the item number is located on the outside of the book. It doesn't have any other information. Say that as a visitor to this library you want to find a book on the Apostle Luke. You look up the information that is specifically related to this subject within the card catalog, and you find an interesting work called A Biography of Luke the Apostle. You notice that the card in the card catalog lists the specific floor, section, aisle, shelf, and item number for this book. It is a book full of text, so its cover is white. You search through the library to locate the correct floor, section, aisle, and shelf. You find the book by locating its item number. Now say you want to find some pictures of the Apostle Luke. You go back to the card catalog,