The NTFS directory is an index of file names. An NTFS index consists of index root, index allocation, and bitmap attributes. Each attribute is named "$I30", probably because it the index is for the attribute 30. The entries in the directory are ordered alphabetically. All entries are converted to upper case before sorting. Upper case is defined by the file $UpCase. Each entry can point to index buffer, which contains more entries that come before this entry. One artificial entry mark the end of an entry list.