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C00002 00002		TENDMP		REG 11-21-74
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	TENDMP		REG 11-21-74


Introduction

TENDMP manipulates PDP-10 (TOPS-10) format DECtapes.  To eliminate
most of the actual tape motion, TENDMP reads the entire tape onto a
disk file and uses the random access facilities of the disk to
simulate dectape.  For writing, TENDMP reads all relevant portions of
the tape to disk, writes new data on the disk file, and then writes
the disk file onto the tape.  This method of operation is much faster
and more reliable than actually reading or writing the tape on record
by record basis. 

The new DATE75 format for TOPS-10 dectapes is implemented in TENDMP.



Using TENDMP

When TENDMP starts it asks "Which Dectape:" and accepts responses
like "3" or "DTA2".  TENDMP will read the tape directory and ask for
a command.  The following commands are available:


Z	Zero the dectape directory.  This needs to be done before using
	a tape for the first time.  It also has the effect of deleting
	all files from the tape.

F	Files.  This commands lists (on the user's terminal) the names
	of the files on the tape.

K	Kill file.  This command deletes a file from the tape.  The K
	must be followed by the character "$" (or altmode will do) and
	by the file name to delete.
	Example:  K$FOO.BAZ  deletes FOO.BAZ from the tape.

S	Create (and preserve) a scratch file.  Normally, for every
	data moving command (P,N,D,L,M) TENDMP will read the entire
	tape to a disk file, operate on the file, and perhaps write
	the entire file to the tape, and delete the scratch file
	before the next command.  What the S command does is to
	create the scratch file immediately, and preserve it from
	one command to the next.  No tape writes will occur until the
	W command is used (except K commands will rewrite the tape
	directory). 

	If a user wants to write several files on one tape, he should
	give the S command, followed by each P command, followed by
	a W command.  Similarly, if a user wants to read several files
	the sequence S, several N command, and an E command should be
	used.

	Further cautions:  After an S command, either a W or an E
	command should be used to clean up.  If the Tape Full message
	occurs during a P (or D or M) operation then the file named
	in the current command will not be written.  If the current
	command was superceding a tape file, then in S mode the 
	old file will be deleted by the next W command, but if not
	in S mode, nothing has happened to the old file.

W	Write the scratch file on tape.  See the S command above.
	

P	Put a file on the tape.  This writes a file from disk to tape.
	The P should be followed by a "$", then the name to write on
	tape, a left arrow, "←", and the name of the disk file.
	Example:  P$FOO.BAZ←ZOTFUB.FAI copies the disk file ZOTFUB.FAI
	onto the tape where it will have the name FOO.BAZ.

N	Retrieve a file from the tape and write it on the disk.  The
	N should be followed by "$", then the name of the file on the
	tape, a right arrow, "→", and the name of the disk file.
	Example:  N$FOO.BAZ→NEWZOT.FUD copies the tape file named FOO.BAZ
	onto the disk where it will have the name NEWZOT.FUD.

N*	Retrieve every file from the tape and write each on the disk
	with the same name it had on the tape.

E	Exit.  This command deletes the scratch file if any is open.

The following commands convert special format files to "TENDMP" zero
compressed format.  The format is not intended for general use, but
is used for loading the timesharing monitor.

D	Write a file on the tape.  The input file should be in system
	DMP format.  The resulting file will be zero compressed SAV
	format, with JOBREL copied to 37, JOBSYM copied to 36, and
	a copy of the 20-LOADER in 20-27.  The right half of JOBSA 
	is used to indicate the starting address.  The syntax is the
	same as P.

M	Write a file on the tape.  The input file should be in MIT
	zero compressed BIN file format.  The initial loader and
	each checksum will be discarded.  The resulting file will
	be in SAV format on the tape.  The syntax is the same as P.

L	Retreive a SAV file from the dectape and write it as a DMP
	file.

If TENDMP does not understand a command, it types out a helpful
message.

Reasonable suggestions for extending TENDMP are solicted, but no major
effort to improve this program is contemplated.