DIRECTORY(V)                 9/10/73                 DIRECTORY(V)


     dir - format of directories


     A directory behaves exactly like an ordinary file, save that

     no user may write into a directory.  The fact that a file is

     a directory is indicated by a bit in the flag  word  of  its

     i-node  entry.   Directory  entries  are 16 bytes long.  The

     first word is the i-number of the file  represented  by  the

     entry, if non-zero; if zero, the entry is empty.

     Bytes 2-15 represent  the  (14-character)  file  name,  null

     padded  on the right.  These bytes are not cleared for empty


     By convention, the first two entries in each  directory  are

     for  ``.''  and  ``..''.   The  first  is  an  entry for the

     directory itself.  The second is for the  parent  directory.

     The  meaning of ``..'' is modified for the root directory of

     the master file system  and  for  the  root  directories  of

     removable  file  systems.   In  the  first case, there is no

     parent, and in the second, the system does not  permit  off-

     device  references.   Therefore in both cases ``..'' has the

     same meaning as ``.''.


     file system (V)