INT 21,6C - Extended Open/Create (DOS 4.x+)

	AH = 6C
	AL = 00
	BX = open mode (see below)
	CX = file attribute (see FILE ATTRIBUTES, bits 15-8 are zero)
	DX = function control indicator (see below)
	DS:SI = ASCIIZ filespec


	returns:
	AX = handle if CF clear
	   = error code if CF set  (see DOS ERROR CODES)
	CX = 01  file opened
	   = 02  file created and opened
	   = 03  file truncated and opened (replaced)
	CF = 0 if successful
	   = 1 if error


	Open Mode in BX:

	|F|E|D|C|B|A|9|8|7|6|5|4|3|2|1|0|  BX  (Open Mode)
	 | | | | | | | | | | | | | `-------- read/write access mode
	 | | | | | | | | | | | | `-------- reserve (must be 0)
	 | | | | | | | | | `------------ sharing mode
	 | | | | | | | | `------------ 1 = private, 0 = inheritable
	 | | | `-------------------- reserved
	 | | `-------------------- 0 = call INT 24, 1 = ignore INT 24
	 | `-------------------- 0 = normal write, 1 = flush each write
	 `-------------------- reserved

	Read/Write Access bits:     Sharing Mode bits:
	210			      654
	000  read access	      000  compatibility mode
	001  write access	      001  read/write access
	010  read/write access	      010  write access denied
				      011  read access denied
				      100  full access

	Function Control Indicator in DX:

	|F|E|D|C|B|A|9|8|7|6|5|4|3|2|1|0|  DX  (Function Control)
	 | | | | | | | | | | | | `---------- file existence behavior
	 | | | | | | | | `----------------- creation behavior
	 `-------------------------------- reserved

	File Existence Behavior bits:
	3210
	0000  if file exist, generate error, take no action
	0001  if file exists, open file
	0010  if file exists, truncate and open


	Creation Behavior bits:
	7654
	0000  if file does not exist, generate error, take no action
	0001  if file does not exist, create