TP(V) 9/10/73 TP(V)
NAME
tp - DEC/mag tape formats
DESCRIPTION
The command tp dumps files to and extracts files from
DECtape 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
program. 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
entry 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
contents 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)