INT 21 - CD-ROM device driver - IOCTL OUTPUT                                    
	AX = 4403h
	BX = file handle referencing character device for CD-ROM driver
	CX = number of bytes to write
	DS:DX -> control block (see #01524)
Return: CF clear if successful
	    AX = number of bytes actually written
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Notes:	some device drivers support several subunits (that is more than one
	  drive) but it is not possible to distinguish between them with this
	  function; use INT 2F/AX=1510h or INT 2F/AX=0802h instead
	under Windows95, the "mscd$$$$" device cannot be opened so you cannot
	  obtain the handle required by this function: use INT 2F/AX=1510h
	  or INT 2F/AX=0802h instead
SeeAlso: AX=4402h"CD-ROM",INT 2F/AX=0802h,INT 2F/AX=1510h


Format of CR-ROM control block:
Offset	Size	Description	(Table 01524)
 00h	BYTE	function code
		00h eject disk
		01h lock/unlock door
		02h reset drive
		03h control audio channel
		04h write device control string
		05h close tray
---functions 00h,02h,05h---
 no further fields
---function 01h---
 01h	BYTE	lock function
		00h unlock door
		01h lock door
---function 03h---
 01h	BYTE	input channel (0-3) for output channel 0
 02h	BYTE	volume for output channel 0
 03h	BYTE	input channel (0-3) for output channel 1
 04h	BYTE	volume for output channel 1
 05h	BYTE	input channel (0-3) for output channel 2
 06h	BYTE	volume for output channel 2
 07h	BYTE	input channel (0-3) for output channel 3
 08h	BYTE	volume for output channel 3
Note:	output channels 0 and 1 are left and right, 2 and 3 are left prime and
	  right prime; a volume of 00h is off
---function 04h---
 01h  N BYTEs	bytes to send directly to the CD-ROM drive without
		  interpretation
                                                                                

INT 21 - Brian Antoine Seagate ST-01 SCSI(Small Computer Systems Interface) A system-independent expansion bus typically used to connect hard disks, tape drives, and CD-ROMs to a computer.	A host adapter connects the SCSI bus to the computer's own bus.  See also ESDI, IDE..SYS - IOCTL - EXECUTE COMMANDS
	AX = 4403h
	BX = handle for device "SCSITAPE"
	CX = number of bytes to write
	DS:DX -> SCSITAPE control block (see #01525)
Return: CF clear if successful
	    AX = number of bytes actually written
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
SeeAlso: AX=4405h"ST-01",INT 78/AH=10h


Format of SCSITAPE control block:
Offset	Size	Description	(Table 01525)
 00h	WORD	command type
		'F' Format (argument 1 = interleave, argument 2 = format type)
		'E' Erase
		'R' Rewind
		'L' Load
		'N' No Load
		'S' Space (argument 1 = count, argument 2 = type)
		'M' File Mark (argument 1 = count)
		'A' Reassign
 02h	WORD	argument 1
 04h	WORD	argument 2
 06h	WORD	segment of command buffer
 08h	WORD	offset of command buffer
 0Ah	WORD	length of command buffer