A TreeView is a common means for displaying and navigating hierarchical structures (like file systems) in a GUI.

BbEdit offers a TreeView.

There's unix program I've come across at an old job, called Tree I think, that does a similar thing at the command line, except instead of a tab delimited tree structure, it gives you combos of | and - to show  the structure.

''Yep, "tree":''
 somebody@somewhere:~$ tree example
 example
 |-- bar
 |   |-- ben.c
 |   `-- bill.c
 `-- foo
     |-- otherfile.txt
     `-- somefile.txt

 2 directories, 4 files



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See TreeMap for a completely different (and much more compact) way to represent a file system (or other hierarchial structures).