Add documentation for old archive format, copied from ARCSAL.

doc/sysdoc/oarcdv.format

@@ -0,0 +1,44 @@
+; ARCHIVE FORMAT
+
+
+; FIRST BLOCK LOOKS ALMOST EXACTLY LIKE A DISK DIRECTORY EXCEPT FOR
+; THE FIRST FOUR WORDS:
+
+;	WORD 0 - ALWAYS -1 TO DISTINGUISH FROM OLD ARCHIVES
+;	WORD 1 - "UDNAMP" RELATIVE POINTER WITHIN DIRECTORY TO
+;		START OF FIRST NAME AREA BLOCK
+;	WORD 2 - "UDESCP" BYTE NUMBER OF NEXT AVAILABLE BYTE IN
+;		DESCRIPTOR AREA
+;	WORD 3 - GC TAG - SYSTEM PACKED DATE/TIME OF LAST REARRANGEMENT
+;		OF DIRECTORY (E.G. DELETION, INSERTION, GARBAGE COLLECTION)
+
+; ONLY OTHER DIFFERENCE FROM STANDARD DISK DIRECTORY IS IN 5TH WORD
+; OF EACH NAME BLOCK.  DISK USES LEFT HALF FOR REFERENCE DATE, DOESN'T
+; USE RIGHT HALF.  ARC USES LEFT HALF FOR REFERENCE DATE, USES RIGHT HALF
+; FOR COUNT OF NUMBER OF OPENS FOR READING.
+
+; SECOND BLOCK:
+
+;	WORD 2000 - ACCESS POINTER TO FIRST BLOCK IN FREE BLOCK CHAIN
+;			(0=>CHAIN IS EMPTY)
+;	WORD 2001 - NUMBER OF FREE WORDS IN ENTIRE ARCHIVE
+;	WORD 2002 - NUMBER OF FREE BLOCKS IN ENTIRE ARCHIVE
+;	WORD 2003 - NUMBER OF WORDS IN USE IN ENTIRE ARCHIVE
+;	WORD 2004 - NUMBER OF BLOCKS IN USE IN ENTIRE ARCHIVE
+;	WORD 2005 - RELATIVE POINTER (RELATIVE TO 2005) TO NEXT AVAILABLE
+;			FBAT ENTRY  (0=>FBAT IS FULL)
+;	WORDS 2006-<2005+200.> - THE FBAT - EACH ENTRY POINTS TO
+;			THE FIRST DATA BLOCK IN A FILE.
+;	WORDS <2005+200.>-EOF - DATA BLOCKS
+
+; A DATA BLOCK:
+
+;	HEADER - 4.9 BIT - 1=>BLOCK IS FREE
+;		 4.8 BIT - 1=>LAST BLOCK IN FILE CHAIN
+;		 4.9,4.8 BITS BOTH 1 => SINGLE WORD OF GARBAGE
+;		 4.7 BIT - UNUSED
+;		 4.6-3.6 - LENGTH-1 OF DATA AREA (NOT INCLUDING HEADER AND TRAILER)
+;		 3.4-1.1 - DISK ADDRESS OF NEXT DATA BLOCK IN THE CHAIN
+
+;	TRAILER - IDENTICAL TO HEADER EXCEPT
+;		 3.4-1.1 - DISK ADDRESS OF PREVIOUS DATA BLOCK IN THE CHAIN