Format of IFS open file structure:
Offset	Size	Description	)
 00h	WORD	???
 02h	WORD	device info word
 04h	WORD	file open mode
 06h	WORD	???
 08h	WORD	file attributes
 0Ah	WORD	owner's network machine number
 0Ch	WORD	owner's PSP segment
 0Eh	DWORD	file size
 12h	DWORD	current offset in file
 16h	WORD	file time
 18h	WORD	file date
 1Ah 11 BYTEs	filename in FCB format
 25h	WORD	???
 27h	WORD	hash value of SFT address
		(low word of linear address + segment&F000h)
 29h  3 WORDs	network info from SFT
 2Fh	WORD	???