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                     OS/8 COMPARE PROGRAM
                          (CMPARE)
 
 
 
                      MARK E. KENDRAT
                    205 BRIARCLIFFE ROAD
                   DEWITT, NEW YORK  13214
	 
	 
	 
	 
	 
	 
	 
	 
	 
	 
	 
	                 ABSTRACT
 
	 
     THE OS/8 FILE UTILITY PROGRAM PROVIDES A
CONVENIENT WAY TO COMPARE TWO FILES ON MASS STORAGE.
("FILES", REFERRING TO INPUT, MAY BE EITHER DIRECTORY-BASED
OS/8 FILES OR EXPLICIT BLOCK NUMBERS).  CORRESPONDING
BINARY WORDS ARE COMPARED AND PROGRAM OUTPUT DETAILS THE
CONTENTS OF MISMATCHES.  OPTIONS EXIST FOR SPECIFYING WORD
LIMITS FOR EACH BLOCK, AND A FAST MODE FOR OUTPUTTING JUST
BLOCK NUMBERS.  OUTPUT IS TO ANY OS/8 DEVICE, OR TO THE
CONSOLE TERMINAL (BY DEFAULT).  THE DEFAULT HANDLER MUST
BE PATCHED FOR ANY DEVICE OTHER THAN THE CONSOLE TERMINAL.
WHEN THE DEFAULT HANDLER IS IN USE, OUTPUT MAY BE SKIPPED
ON A BLOCK-BY-BLOCK BASIS.  CMPARE OPTIMIZES PERFORMANCE
BY ALTERNATING THE LOADING OF INPUT BUFFERS.  ALSO, BUFFER
SPACE IS INCREASED ON A 12K MACHINE. 
 
 
                         REQUIREMENTS
 
 
     ANY PDP-8 WITH OS/8, AND THE DEVICES AND THEIR HANDLERS
FOR THE INPUT FILES.  CORE LAYOUT FOR 8K VS. 12K MAY BE
FOUND IN THE SOURCE, AS WELL AS THE CODE FOR THE DEFAULT
HANDLER.  TO USE ANY DEVICE OTHER THAN THE CONSOLE TERMINAL
AS THE DEFAULT DEVICE, THE PROGRAM MUST BE PATCHED.
 
 
 
 
 
 
 
 
 
 
 
 
                     OPERATING PROCEDURES
 
 
LOADING AND STARTING CMPARE
 
     LOAD CMPARE.SV, WHICH WILL IDENTIFY ITSELF ON THE DE-
FAULT DEVICE.  BUFFER SPACE WILL THEN BE OPTIMIZED IF
FIELD 2 EXISTS.  THE COMMAND DECODER WILL THEN BE USED TO
ACCEPT COMMANDS.  WHEN THE COMMAND HAS BEEN CARRIED OUT,
CMPARE WILL RESTART. 
 
COMMAND DECODER INPUT
 
     COMMAND DECODER INPUT IS OF THE FORM:
 
DEV:OUTFIL<DEV:ASPEC,DEV:BSPEC,FIRST,LAST/OPTIONS=N
 
     NOTE:  IN THE DISCUSSION THAT FOLLOWS, "FILE A" AND
"FILE B" REFER TO THE TWO INPUT FILES, BE THEY DIRECTORY-
BASED OR BLOCK SPECIFICATIONS.
 
     THE COMPONENTS OF COMMAND DECODER INPUT ARE:
 
DEV:OUTFIL	ALL OUTPUT, EXCEPT FOR ERROR MESSAGES AND
		INITIAL IDENTIFICATION, IS SENT TO THE
		SPECIFIED FILE.  IF ONE IS NOT SPECIFIED,
		OUTPUT IS SENT VIA AN INTERNAL HANDLER
		(REFERRED TO AS THE DEFAULT HANDLER.)
 
ASPEC,BSPEC	THESE MAY BE OS/8 FILE NAMES OR EXPLICIT
		BLOCK NUMBERS (OCTAL).  SWITCH OPTIONS
		(SEE "/B" AND "/C", BELOW) SPECIFY WHETHER
		THEY ARE BLOCK NUMBERS.  THEY ARE FILE
		NAMES BY DEFAULT.
 
FIRST		AN OCTAL NUMBER, SPECIFYING THE FIRST
		WORD (OF EACH BLOCK) THAT IS TO BE COM-
		PARED.  IF OMITTED, THE FIRST WORD IS 000.
 
LAST		AN OCTAL NUMBER, SPECIFYING THE LAST WORD
		(OF EACH BLOCK) THAT IS TO BE COMPARED.
		IF OMITTED, THE LAST WORD IS 377.  SPE-
		CIFY BOTH LIMITS IF THERE ARE ANY.
 
 
 
 
 
 
 
 
 
 
 
 
 
OPTIONS
 
/B		INTERPRET BSPEC AS BEING AN EXPLICIT BLOCK
		NUMBER FOR THE FIRST BLOCK OF FILE B, AND
		ASPEC AS A FILE NAME.  THE LENGTH OF FILE A
		IS USED AS THE NUMBER OF BLOCKS TO COMPARE
		(SEE =N, BELOW.) 
 
/C		INTERPRET BOTH ASPEC AND BSPEC AS EXPLICIT
		BLOCK NUMBERS (SEE =N, BELOW).
 
 
/F		FAST MODE.  OUTPUT ONLY THE BLOCK HEADERS,
		NOT THE CONTENTS OF EACH PAIR OF NON-MATCH-
		ING WORDS (SEE "OUTPUT", BELOW.)
 
=N		UNCONDITIONALLY SET THE NUMBER OF BLOCKS
		TO COMPARE TO N.  THIS IS USED TO SPECIFY
		HOW MANY BLOCKS TO COMPARE IF BOTH FILES
		ARE EXPLICIT BLOCK SPECIFICATIONS.  IF TWO
		BLOCK SPECIFICATIONS ARE GIVEN, N IS 1 BY
		DEFAULT.
 
 
 
 
 
 
 
 
 
 
 
 
                            OUTPUT
 
 
 
     A HEADER LINE IS OUTPUT FOR EACH BLOCK OF FILE A THAT
DOES NOT MATCH THE CORRESPONDING BLOCK OF FILE B.  THIS IS
THE ONLY OUTPUT IF SWITCH F IS SELECTED (SEE "/F", ABOVE).
THE HEADER LINE IS OF THE FORM:
 
BLK  ABLK BBLK (REL)
 
WHERE ABLK AND BBLK ARE BLOCK NUMBERS INDICATING THE BLOCKS
THAT DO NOT MATCH.  REL IS THE BLOCK NUMBER RELATIVE TO THE
STARTING BLOCKS OF THE INPUT FILES.
 
     EACH PAIR OF WORDS THAT IS NOT A MATCH CAUSES A LINE
TO BE OUTPUT UNDER THE APPROPRIATE BLOCK HEADER.  IT IS OF
THE FORM:
 
ADR/ AWORD BWORD
 
WHERE ADR IS THE ADDRESS OF THE WORDS, RELATIVE TO THE BLOCK
DENOTED IN THE BLOCK HEADER.  AWORD AND BWORD ARE THE VAL-
UES OF THE TWO NON-MATCHING WORDS.
 
     WHEN ONE OR BOTH FILES RUN OUT, AN APPROPRIATE MESS-
AGE IS OUTPUT.  IT WILL BE ONE OF:
 
EOFA		FILE A RAN OUT BEFORE FILE B.
EOFB		FILE B RAN OUT BEFORE FILE A.
EOF		THE FILES RAN OUT SIMULTANEOUSLY.
EOFM		THE FILES MATCH!
 
AFTER THE END-OF-FILE MESSAGE IS OUTPUT, THE PROGRAM RESTARTS.
 
 
 
 
 
 
 
 
 
 
 
 
                            ERRORS
 
 
     WHEN AN ERROR IS DETECTED, A MESSAGE IS OUTPUT VIA
THE DEFAULT DEVICE HANDLER.  THE PROGRAM IS THEN RESTARTED.
ERROR MESSAGES ARE OF THE FORM:
 
?DDD
 
WHERE DDD IS AN ERROR NUMBER. THE FOLLOWING TABLE EXPLAINS
THE ERROR NUMBERS:
 
001	PHYSICAL READ ERROR, FILE A.
002	PHYSICAL READ ERROR, FILE B.
003	PHYSICAL WRITE ERROR, OUTPUT FILE.
004	ERROR IN ENTERING OUTPUT FILE.
005	ERROR IN FETCHING HANDLER FOR FILE A.
006	ERROR IN FETCHING HANDLER FOR FILE B.
007	ERROR IN FETCHING HANDLER FOR OUTPUT FILE.
010	LOOKUP ERROR, FILE A.
011	LOOKUP ERROR, FILE B.
012	BAD BLOCK NUMBER SPECIFIED FOR FILE A.
013	BAD BLOCK NUMBER SPECIFIED FOR FILE B.
014	CLOSE ERROR ON OUTPUT FILE.
015	OUTPUT FILE OVERFLOW. 
	 
	 
                        CONTROL CHARACTERS
 
 
     THE FOLLOWING TABLE LISTS AVAILABLE CONTROL CHARACTERS.
THEY SHOULD BE TYPED ON THE CONSOLE TERMINAL.
 
CHARACTER	ACTION
 
CTRL/C		BOOTSTRAP OS/8.
CTRL/P		RESTART PROGRAM.
CTRL/N		IF TYPED DURING THE OUTPUT OF DIFFERENCES, THE
		BLOCK CURRENTLY BEING OUTPUT WILL BE SKIPPED.
		A LINE CONTAINING A "*" WILL BE OUTPUT TO INDI-
		CATE THIS.  NOTE THAT THE DEFAULT HANDLER DOES
		NOT BUFFER DATA, AND A USER-SPECIFIED HANDLER
		DOES.  THUS, CTRL/N IS USEFUL ONLY WHEN	THE
		DEFAULT HANDLER IS IN USE, AS THE USER CAN
		IMMEDIATELY SEE THE EFFECTS OF CTRL/N.
 
78/11/23/00:22  (002) MEK