A hierarchical (page 935) structure frequently takes the shape of a pyramid. One example of this type of structure is found by tracing a family's lineage: A couple has a child, who may in turn have several children, each of whom may have more children. This hierarchical structure is called a family tree (Figure 4-1).
Figure 4-1. A family tree
Like the family tree it resembles, the Mac OS X filesystem is called a tree. It consists of a set of connected files. This structure allows you to organize files so you can easily find any particular one. On a standard Mac OS X system, each user starts with one directory, to which the user can add subdirectories to any desired level. By creating multiple levels of subdirectories, a user can expand the structure as needed.
Typically each subdirectory is dedicated to a single subject, such as a person, project, or event. The subject dictates whether a subdirectory should be subdivided further. For instance, Figure 4-2 shows a secretary's subdirectory named correspond. This directory contains three subdirectories: business, memos, and personal. The business directory contains files that store each letter the secretary types. If you expect many letters to go to one client, as is the case with milk_co, you can dedicate a subdirectory to that client.
Figure 4-2. A secretary's directories
One strength of the Mac OS X filesystem is its ability to adapt to users' needs. You can take advantage of this strength by strategically organizing your files so they are most convenient and useful for you.