FCB - Standard DOS File Control Block

      Offset Size		Description

	-7   byte	if FF this is an extended FCB  ╪
	-6  5bytes	reserved  ╪
	-1   byte	file attribute if extended FCB	╪
	00   byte	drive number (0 for default drive, 1=A:, 2=B:, ...)
	01  8bytes	filename, left justified with trailing blanks
	09  3bytes	filename extension, left justified w/blanks
	0C   word	current block number relative to beginning of the
			file, starting with zero
	0E   word	logical record size in bytes
	10   dword	file size in bytes
	14   word	date the file was created or last updated

		│F│E│D│C│B│A│9│8│7│6│5│4│3│2│1│0│ 15,14 (Intel reverse order)
		 │ │ │ │ │ │ │ │ │ │ │ └─┴─┴─┴─┴─ day 1-31
		 │ │ │ │ │ │ │ └─┴─┴─┴────────── month 1-12
		 └─┴─┴─┴─┴─┴─┴───────────────── year + 1980

	16   word	time of last write

		│F│E│D│C│B│A│9│8│7│6│5│4│3│2│1│0│ 17,16 (Intel reverse order)
		 │ │ │ │ │ │ │ │ │ │ │ └─┴─┴─┴─┴── secs in 2 second increments
		 │ │ │ │ │ └─┴─┴─┴─┴─┴─────────── minutes (0-59)
		 └─┴─┴─┴─┴────────────────────── hours (0-23)

	18  8bytes	see below for version specific information  ╪
	1A   dword	address of device header if character device  ╪
	20   byte	current relative record number within current BLOCK
	21   dword	relative record number relative to the beginning of
			the file, starting with zero; high bit omitted if
			record length is 64 bytes


DOS 2.x Values for reserved fields at offsets 18h-1Ah	╪

      Offset Size		Description
	18   byte	│7│6│5│4│3│2│1│0│
			 │ │ └─┴─┴─┴─┴─┴─── unknown
			 │ └────────────── 1 = open
			 └─────────────── 1 = logical device

	19   word   	starting cluster number  ╪


DOS 3.x Values for reserved fields at offsets 18h-19h	╪

      Offset Size		Description
	18   byte	System File Table (SFT) entry for file	╪
	19   byte	attributes  ╪

			│7│6│5│4│3│2│1│0│  attributes
			 │ │ └─┴─┴─┴─┴─┴──── unknown
			 └─┴─ share status

			00 = SHARE not loaded block device
			01 = SHARE not loaded characted device
			10 = SHARE loaded, remote file
			11 = SHARE loaded local file


DOS 3.x with SHARE, local file reserved offsets 1Ah-1Eh  ╪

      Offset Size		Description
	1A   word	starting cluster number
	1C   word	offset within SHARE of sharing record
	1E   byte	file attribute


DOS 3.x with SHARE, remote file reserved offsets 1Ah-1Eh  ╪

      Offset Size		Description
	1A   word	sector number containing directory entry
	1C   word	last cluster accessed relative to beginning of file
	1E   byte	absolute cluster number of last cluster accessed


DOS 3.x without SHARE reserved offsets 1Ah-1Fh  ╪

      Offset Size		Description
	1A   byte	((device attribute word low byte) & 0Ch) || (open mode)
	1B   word	starting cluster number
	1D   word	sector number containing directory entry
	1F   byte	number of directory entry within sector


 	The following are FCB related DOS functions:

	INT 21,F   Open file using FCB
	INT 21,10  Close file using FCB
	INT 21,11  Search for first entry using FCB
	INT 21,12  Search for next entry using FCB
	INT 21,13  Delete file using FCB
	INT 21,14  Sequential read using FCB
	INT 21,15  Sequential write using FCB
	INT 21,16  Create a file using FCB
	INT 21,17  Rename file using FCB
	INT 21,21  Random read using FCB
	INT 21,22  Random write using FCB
	INT 21,23  Get file size using FCB
	INT 21,24  Set relative record field for FCB
	INT 21,27  Random block read using FCB
	INT 21,28  Random block write using FCB
	INT 21,29  Parse filename for FCB


	╪  see Bibliography reference to "Undocumented DOS"

	- see	XFCB   INT 21,52