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 name32 bytes

mode2 bytes

uid1 byte

gid1 byte

unused1 byte

size3 bytes

time modified4 bytes

tape address2 bytes

unused16 bytes

check sum2 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)