@Tables and Formats used by DOS & BIOS
:backup headers
^DOS BACKUP Control Information

%	BACKUPID.@@@ Format

%     Offset Size		Description
	00   byte   Disk sequence flag:
			00  indicates disk is not the last backup diskette
			FF  indicates disk is the last backup diskette
	01   word   Floppy disk sequence number (Intel format)
	03   word   Backup year, four digits (Intel format)
	05   byte   Day of month (1-31)
	06   byte   Month of year (1-12)
	07   dword  System time if /T was specified (see ~FILE ATTRIBUTES~)
	0B 117bytes Unused


%	Backup File Header

%     Offset Size		Description
	00   byte   Disk sequence flag:
			00  indicates disk is not the last backup diskette
			FF  indicates disk is the last backup diskette
	01   byte   Floppy disk sequence number
	02  3bytes  Unused
	05 64bytes  Full pathname (without drive designator)
	45 14bytes  Unused
	53   byte   Length of file path name at offset 05 plus 1
	54 44Bytes  Unused
:BIOS Parameter Block:BPB
^BPB - BIOS Parameter Block

%     Offset Size	    Description

	00   word	sector size in bytes
	02   byte	sectors per cluster (allocation unit size)
	03   word	number of reserved sectors
	05   byte	number of FATs on disk
	06   word	number of root directory entries (directory size)
	08   word	number of total sectors; if partition > 32Mb then set
			to zero and dword at 15h contains the actual count
	0A   byte	media descriptor byte  (see ~MEDIA DESCRIPTOR~)
	0B   word	sectors per ~FAT~

%	Additional/different fields for DOS 3.0+
	0D   word	sectors per track
	0F   word	number of heads
	11   word	number of hidden sectors
	15 11bytes	reserved

%	Additional/different fields for DOS 4.0+
	15   dword	number of total sectors if offset 8 is zero
	19  6bytes	reserved
	1F   word	number of cylinders
	21   byte	device type
	22   word	device attributes

	- located in the boot sector at offset 0Bh

	- see	~BOOT SECTOR~
:Batch Control Block:BCB
^BCB - Batch Control Block (undocumented)

^DOS 2.x thru DOS 3.2  BCB Format

%     Offset Size		   Description

	00   byte	unknown
	01   word	if non-zero; segment of control block for active FOR
	03   byte	type of batch command
			    0 - normal batch command
			    1 - FOR-loop active
	04   dword	offset of next command to execute in batch file
	07   word	offset of variable %0 (batch file name)
	09  9 words	offset of %N batch file parameters, 0FFFFh indicates
			parameter is null
	1C   nbytes	null terminated path and filename of the current
			batch file immediately followed by command line
			parameters.  Each parameter %0-%9 plus a CR is
			appended and resulting string is null terminated.


^DOS 3.3  BCB Format

%     Offset Size		   Description

	00   byte	unknown
	01   byte	global echo switch, if exec'd by batch CALL-command
			    1 - turn ECHO ON on return to calling batch file
			    0 - turn ECHO OFF on return to calling batch file
	02   word	batch file BCD segment if executed via CALL
			    if zero; batch file was called from command line
			    if non-zero; batch file executed via CALL-command
	04   word	if non-zero; segment of control block for active FOR
	06   byte	type of batch command
			    0 - normal batch command
			    1 - FOR-loop active
	07   dword	offset of next command to execute in batch file
	0B   word	offset of variable %0 (batch file name)
	0D  9words	offset of %N batch file parameters, 0FFFFh indicates
			parameter is null
	1F  nbytes	null terminated path and filename of the current
			batch file immediately followed by command line
			parameters.  Each parameter %0-%9 plus a CR is
			appended and resulting string is null terminated.


	- BCB length is variable and depends on the size and count of the
	  parameters and fully qualified batch file name
	- the MCB for a BCB has a process Id of the transient portion of
	  the latest COMMAND.COM
	- offsets displayed are relative to the BCB segment
	- SHIFT command changes the offsets of the parameters in the table
	  at the offsets 0B0h thru 1Ch
	- BCB  of DOS 3.3 is the  same as earlier versions except 3 bytes
	  were added after offset 0
	- to find a BCB, locate the first block in the MCB chain belonging
	  to COMMAND.COM (the second allocated block always belongs to
	  COMMAND.COM).  Then scan the ~MCB~ chain for a 64 byte block with
	  the same owner ID as COMMAND.COM).  This will be the BCB.
:BIOS Data Area:BDA:BIOS memory:memory map
^BDA - BIOS Data Area - PC Memory Map

%	Address Size	   Description

	00:00 256dwords Interrupt vector table
	30:00 256bytes	Stack area used during post and bootstrap
	40:00	word	COM1 port address
	40:02	word	COM2 port address
	40:04	word	COM3 port address
	40:06	word	COM4 port address
	40:08	word	LPT1 port address
	40:0A	word	LPT2 port address
	40:0C	word	LPT3 port address
	40:0E	word	LPT4 port address (except PS/2)
			Extended BIOS Data Area segment (PS/2, see ~EBDA~)
	40:10  2 bytes	Equipment list flags (see ~INT 11~)