ES:(E)BX -> modified buffer (AL=01h on entry)
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
Notes:	BX/DX are used in V86 mode, EBX/EDX in native mode
	the file class cannot be changed for files because it affects the
	  encryption method, but directories can have their classes changed

Format of PC-MOS/386 directory information:
Offset	Size	Description	(Table 04005)
 00h	BYTE	reserved (0)
 01h	BYTE	file class ('A'-'Z' or 00h)
 02h	DWORD	user ID of file creator
 06h	WORD	file creation time (see #01665 at INT 21/AX=5700h)
 08h	WORD	file creation date (see #01666 at INT 21/AX=5700h)
--------O-D404-------------------------------
INT D4 - PC-MOS/386 v3.0+ - GET TASK CONTROL BLOCK
	AH = 04h
	BX = task ID or FFFFh for calling task
Return: CF clear if successful
	    ES = segment of Task Control Block (TCB) (see #04006)
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
Note:	superseded by AH=27h
SeeAlso: AH=02h,AH=27h,AH=28h,AH=29h,AH=2Ah,INT 38

Format of PC-MOS/386 Task Control Block:
Offset	Size	Description	(Table 04006)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "T" = TCB
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---TCB---
 10h	WORD	TCB task ID
 12h	WORD	native context save area
 14h	WORD	start address of task
 16h	WORD	end address of task
 18h	BYTE	task priority
 19h	BYTE	task time slice
 1Ah	BYTE	"TCBWAIT" run status of task
 1Bh	BYTE	"TCBSTAT" what the task is waiting for
 1Ch	DWORD	address of polling routine
 20h	BYTE	error code from last function call
 21h 11 BYTEs	name of currently executing task
 2Ch  4 BYTEs	???
 30h	BYTE	keyboard disabled if bit 1 set
 31h	BYTE	current shift state and toggles
 32h  2 BYTEs	???
 34h	BYTE	current video mode
 35h	BYTE	current video page
 36h	BYTE	number of text columns per screen
 37h	BYTE	number of text rows per screen
 38h	WORD	length of video buffer
 3Ah	WORD	video page length
 3Ch	WORD	apge start address in video RAM
 3Eh  4 WORDs	current cursor positions for four screen pages
 46h  8 BYTEs	???
 4Eh	WORD	current cursor type
 50h	BYTE	current palette setting
 51h	BYTE	original video mode
 52h	BYTE	start CRT row (00h or 01h)
 53h	BYTE	video RAM in task active
 54h	WORD	handle of video save area
 56h	WORD	page count of video save area
 58h	WORD	segment address of video save area
 5Ah	WORD	poitner to first Task File Block (see #04009)
 5Ch	WORD	pointer to first Current Directory Block (see #04012)
 5Eh	WORD	pointer to active Current Directory Block (see #04012)
 60h	BYTE	number of drives
 61h	BYTE	current drive (0=A:, etc.)
 62h	DWORD	disk transfer address
 66h  4 BYTEs	???
 6Ah	BYTE	verify flag (nonzero = on)
 6Bh	BYTE	break flag (nonzero = on)
 6Ch	WORD	share/lock retry count
 6Eh	WORD	ticks between share/lock retries
 70h	BYTE	remote printer flags (see #04007)
 71h	BYTE	ETX/ACK delay count
 72h	WORD	spooler segment address
 74h  2 BYTEs	???
 76h  3 BYTEs	remote printer redirection for LPT1 through LPT3 (see #04008)
 79h  2 BYTEs	???
 7Bh	DWORD	offset of username in TCB
 7Fh	BYTE	current output class
 80h  7 BYTEs	protection access rights, 2 bits per class (writeable!)
 87h 122 BYTEs	???
101h	BYTE	TCB sleep downcounter value
102h 20 BYTEs	???
116h	BYTE	last scan code
	...
5D0h	DWORD	far pointer to Device Driver Terminal's entry point
5D4h	WORD	offset of logical screen
5D6h	WORD	segment of logical screen
5D8h	WORD	cursor offset within page
5DAh	BYTE	screen columns
5DBh	WORD	async port number (0000h = none)
5DDh	DWORD	physical baudrate
5E1h 19 BYTEs	reserved for Device Driver Terminal (DDT)
	...
7A6h	DWORD	far pointer to unregister calling chain

Bitfields for PC-MOS/386 remote printer flags:
Bit(s)	Description	(Table 04007)
 0	LPT1 to terminal
 1	LPT2 to terminal
 2	LPT3 to terminal
 3	escape to printer pending
 4	use XON/XOFF
 5	use ETX/ACK
 6	waiting for ACK or XON
 7	transparent printing on

(Table 04008)
Values for PC-MOS/386 remote printer redirection:
 00h	not redirected
 01h	redirected to COM1
 ...
 18h	redirected to COM24
 51h	redirected to LPT1
 52h	redirected to LPT2
 53h	redirected to LPT3

Format of PC-MOS/386 Task File Block:
Offset	Size	Description	(Table 04009)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "F" = task file block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---TFB---
 10h	WORD	segment address of next TFB
 12h	WORD	segment address of previous TFB
 14h	WORD	segment address of TFB's Global File Block (see #04011)
 16h	WORD	segment address of owner's PSP
 18h	WORD	file handle
 1Ah  3 BYTEs	???
 1Dh	DWORD	file position
 21h  4 BYTEs	???
 25h	BYTE	IOCTL flags (see #04010)
 26h  2 BYTEs	???

Bitfields for PC-MOS/386 IOCTL flags:
Bit(s)	Description	(Table 04010)
 0	stdin
 1	stdout
 2	null device
 3	clock device
 4	reserved
 5	ASCII mode instead of binary
 6	EOF encountered on input
 7	device rather than file

Format of PC-MOS/386 Global File Block:
Offset	Size	Description	(Table 04011)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "G" = global file block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---GFB---
 10h 10 BYTEs	???
 1Ah	WORD	file attribute
 1Ch	BYTE	???
 1Dh	DWORD	address of device driver
 21h	WORD	first cluster
 23h	WORD	time of last modification
 25h	WORD	date of last modification
 27h	DWORD	size of file in bytes
 2Bh 11 BYTEs	???
 36h 11 BYTEs	device name or FCB-format filename
 41h	WORD	segment address of TFB list
 43h	WORD	segment address of first RLB (see #04014) (0000h = none)
 45h	BYTE	flag: nonzero if GFB refers to character device
 46h	WORD	address of Block Device Block (see #04013)
 48h	WORD	sector of file's directory entry (see #01352)
 4Ah	WORD	high word of file's directory entry
 4Ch	WORD	ofsset of directory entry within sector

Format of PC-MOS/386 Current Directory Block:
Offset	Size	Description	(Table 04012)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "C" = current directory block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---CDB---
 10h	BYTE	drive number
 11h	BYTE	???
 12h 64 BYTEs	directory name
 52h	WORD	first directory cluster (0000h = root)

Format of PC-MOS/386 Block Device Block:
Offset	Size	Description	(Table 04013)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "B" = block device block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---BDB---
 10h	BYTE	logical drive
 11h	BYTE	unit passed to driver
 12h	WORD	sector size
 14h	BYTE	cluster mask
 15h	BYTE	cluster shift count
 16h	WORD	starting sector of first FAT
 18h	BYTE	number of FATs
 19h	WORD	number of root directories
 1Bh	WORD	sector number of first data sector (cluster 0002h)
 1Dh	WORD	number of clusters + 1 (number of highest data cluster)
 1Fh	BYTE	number of sectors in FAT
 20h	WORD	beginning root directory sector number
 22h	DWORD	device driver address
 26h	BYTE	media descriptor byte
 27h  5 BYTEs	???
 2Ch	BYTE	flag: volume > 32MB
 2Dh	BYTE	???
 2Eh	BYTE	number of sectors per cluster
 2Fh	WORD	number of clusters on device
 31h	WORD	number of free clusters (FFFFh = unknown)
 33h	WORD	root directory cluster number
 35h	WORD	pointer to alias/subst string
 37h	WORD	TCB segment address of owner (0000h = none)

Format of PC-MOS/386 Record Lock Block:
Offset	Size	Description	(Table 04014)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "R" = record lock block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---RLB---
 10h	WORD	segment address of owner's PSP
 12h	WORD	segment address of Global File Block (see #04011)
 14h	WORD	segment address of owner's Task File Block (see #04009)
 16h	DWORD	file offset of locked region start
 1Ah	DWORD	length of locked region
 1Eh	WORD	owner's handle for file
--------O-D407-------------------------------
INT D4 - PC-MOS/386 v3.0+ - WAIT FOR EVENT
	AH = 07h
	AL = events to monitor (see #04015)
	BX = number of timer ticks until timeout if AL bit 1 set
	CX = bitmap of IRQs to monitor if AL bit 2 set
		(bit 0 = IRQ0 .. bit 15 = IRQ15)
	DX = port to monitor if AL bit 3 set
Return: CF clear if successful
	    AL = type of event which woke up task (see #04015)
	    CX = IRQ (if any) which awakened task
	    DX = port (if any) which awakened task
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
Note:	a device driver may make this call with AL=00h, which indicates that
	  the driver is responsible for setting and clearing the TCBWAIT field
	  in the TCB.  To put task to sleep, set TCBWAIT bits 2-0 to 001; to
	  reawaken it, set bit 1 (leaving other bits unchanged)
SeeAlso: AH=04h,INT 16/AH=00h,INT 38

Bitfields for PC-MOS/386 events to monitor:
Bit(s)	Description	(Table 04015)
 0	keystroke
 1	timeout
 2	IRQ
 3	port access
 7	return status of user poll routine (other ignored if set)
--------O-D410-------------------------------
INT D4 - PC-MOS/386 v3.0+ - ENTER/LEAVE NATIVE 386 EXECUTION MODE
	AH = 10h
	AL = direction (00h return to V86 mode, 01h enter native mode)
	CX = length in bytes of Native Context Area ( >=1024 )
	DX = segment of Native Context Area
Return: CF clear if successful
	    running in desired mode at instruction following INT D4 call
	    all segment registers converted to appropriate selectors/segments
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
Note:	MS-DOS calls are available in protected mode
SeeAlso: AH=11h,AH=12h,AH=13h,INT 2F/AX=1687h,INT 67/AX=DE0Ch,INT 38
--------O-D411-------------------------------
INT D4 - PC-MOS/386 v3.0+ - ALLOCATE NATIVE MODE MEMORY BLOCK
	AH = 11h
	EBX = block length in bytes
Return: CF clear if successful
	    EBX = number of bytes actually allocated
	    ES = selector for allocated block
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
Program: PC-MOS/386 is a multitasking/multiuser MS-DOS-compatible operating
	  system by The Software Link, Inc.
Note:	the memory must be released before the program terminates
SeeAlso: AH=10h,AH=12h,INT 38
--------O-D412-------------------------------
INT D4 - PC-MOS/386 v3.0+ - FREE NATIVE MODE MEMORY BLOCK
	AH = 12h
	ES = selector for block to free
Return: CF clear if successful
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
SeeAlso: AH=10h,AH=11h,AH=13h,INT 38
--------O-D413-------------------------------
INT D4 - PC-MOS/38