Filesystems consider a directory as a special file. They represent a directory or a folder with an on-disk inode. They are differentiated from normal file inodes through the type field, which is marked as directory. Each directory is assigned data blocks where it holds information about files and subdirectories it contains. A directory maintains records of files, and each record includes the filename, which is a name string not exceeding a specific length as defined by the filesystem's naming policy, and the inode number associated with the file. For efficient management, filesystem implementations define the layout of file records contained in a directory through appropriate data structures such as binary trees, lists, radix trees, and hash tables: