figure small part of the unix file system hierarchy third property is that each leaf node is unique we can specify path from the root of the tree to leaf that uniquely identifies each species in the animal kingdomfor exampleanimalia chordate mammal carnivora felidae felis domestica another example of tree structure that you probably use every day is file system in file systemdirectoriesor foldersare structured as tree figure illustrates small part of unix file system hierarchy the file system tree has much in common with the biological classification tree you can follow path from the root to any directory that path will uniquely identify that subdirectory (and all the files in itanother important property of treesderived from their hierarchical natureis that you can move entire sections of tree (called subtreeto different position in the tree without affecting the lower levels of the hierarchy for examplewe could take the entire subtree staring with /etc/detach etcfrom the root and reattach it under usrthis would change the unique pathname to httpd from /etc/httpd to /usr/etc/httpdbut would not affect the contents or any children of the httpd directory final example of tree is web page the following is an example of simple web page written using html figure shows the tree that corresponds to each of the html tags used to create the page <meta http-equiv="content-typecontent="text/htmlcharset=utf- /simple simple web page list item one list item two the html source code and the tree accompanying the source illustrate another hierarchy notice that each level of the tree corresponds to level of nesting inside the html tags the first tag in the source is and the last is all the rest of the tags in the page are examples of trees