1	!


	!		N U L L 



2!		Program:	NULL
3!		Version:	V01A
4!		Edit:		01
7!		Edit Date:	18-Jun-80
9!		Author:		Brant Cheikes


20	!


	!	M o d i f i c a t i o n   H i s t o r y


	!	Version/Edit	Edit Date	Reason

21!		V01A-01		18-Jun-80	New release

50	!


	!	P r o g r a m   D e s c r i p t i o n



60	!
	!  NULL writes zeros on a magnetic tape, zeroing it completely, and
	!  writes a LEOT at BOT to perform a normal zero operation.  It
	!  removes all sorts of garbage from a magtape, insuring safety of
	!  data stored on the tape.
	!

1000	!


	!	M a i n   P r o g r a m   C o d i n g



1010	V$ = "V01A-01"
	!  Set up version/edit level

1020	ON ERROR GOTO 30000
	\  PRINT
	\  PRINT "NULL   "+V$+"   "+
	   CVT$$(RIGHT(SYS(CHR$(6%)+CHR$(9%)),3%),4%)
	\  PRINT "Magtape Eraser"
	\  PRINT
	!  Output the system header

1025	OPEN "MM0:" AS FILE 1%, RECORDSIZE 8192%, MODE 12%
	!  Open magtape

1027	INPUT "Detach";D$
	\  PRINT
	\  GOTO 1030 UNLESS D$ = "Y"
	\  PRINT "Detaching..."
	\  PRINT CHR$(12%);
	\  S$ = SYS(CHR$(6%)+CHR$(7%))
	\  D% = -1%
	\  GOTO 1040
	!  Allow detached processing

1030	PRINT "Erasing MM0:, wait please..."
	\  PRINT

1040	FIELD #1%, 8192% AS B$
	\  I% = MAGTAPE(3%,0%,1%)
	!  Field buffer and rewind tape

1045	LSET B$ = STRING$(8192%,0%)
	!  Null out buffer

1050	PUT #1%
	\  GOTO 1050

30000	!


	!	E r r o r   H a n d l i n g



30010	IF ERR = 4% THEN I% = MAGTAPE(3%,0%,1%)
	\  I% = MAGTAPE(2%,0%,1%) FOR C% = 1% TO 3%
	\  I% = MAGTAPE(3%,0%,1%)
	\  CLOSE #1%
	\  RESUME 32000 IF D%
	\  PRINT "Magnetic tape on drive 0 has been erased and zeroed."
	\  RESUME 32000
	!  When we run out of room, rewind the tape; write LEOT (3 tapemarks);
	!  rewind tape again, close it, tell user and exit

30020	IF ERL = 1025% THEN PRINT CHR$(7%);CHR$(7%);CHR$(7%);
	\  PRINT "Please mount tape to be zeroed on drive 0"
	\  PRINT "Hit the RETURN key to proceed"
	\  GET
	\  PRINT
	\  RESUME 1025
	!  Handle tape not mounted errors

30030	IF ERR = 39% AND ERL = 1050% THEN PRINT CHR$(7%);
	\  RESUME 32000 IF D%
	\  PRINT "Magnetic tape on drive has no EOT mark - please fix it"
	\  CLOSE #1%
	\  RESUME 32000

30900	RESUME 32000 IF D%
	\  PRINT "?Error erasing tape - ";
	CVT$$(RIGHT(SYS(CHR$(6%)+CHR$(9%)+CHR$(ERR)),3%),4%);
	" (ERR=";NUM1$(ERR);") at line";ERL
	\  CLOSE #1%
	\  RESUME 32000

32000	!


	!	E x i t



32010	S$ = SYS(CHR$(6%)+CHR$(5%)) IF D%
	!  Logout if detached

32700	S$ = SYS(CHR$(9%))
	!  Clear core and exit fast

32767	END