    TP(V)                        9/10/73                        TP(V)

    NAME
         tp - DEC/mag tape formats

    DESCRIPTION
         The  command  tp dumps files to and extracts files from DEC-
         tape and magtape.  The formats of these tapes are  the  same
         except that magtapes have larger directories.

         Block  zero  contains a copy of a stand-alone bootstrap pro-
         gram.  See boot procedures(VIII).

         Blocks 1 through 24 for DECtape (1 through 62  for  magtape)
         contain  a directory of the tape.  There are 192 (resp. 496)
         entries in the directory; 8 entries per block; 64 bytes  per
         entry.  Each entry has the following format:

             path name           32 bytes
             mode                2 bytes
             uid                 1 byte
             gid                 1 byte
             unused              1 byte
             size                3 bytes
             time modified       4 bytes
             tape address        2 bytes
             unused              16 bytes
             check sum           2 bytes

         The path name entry is the path name of the file when put on
         the tape.  If the pathname starts with a zero word, the  en-
         try  is  empty.   It  is at most 32 bytes long and ends in a
         null byte.  Mode, uid, gid, size and time modified  are  the
         same as described under i-nodes (file system(V)).  The tape
         address is the tape block number of the start  of  the  con-
         tents  of  the file.  Every file starts on a block boundary.
         The file occupies (size+511)/512 blocks of continuous  tape.
         The  checksum  entry has a value such that the sum of the 32
         words of the directory entry is zero.

         Blocks 25 (resp. 63) on are available for file storage.

         A fake entry (see tp(I)) has a size of zero.

    SEE ALSO
         file system(V), tp(I)

                                  - 1 -