Function  2Fh  Get Disk Transfer Address (DTA) 
     Returns current disk transfer address used by all DOS read/write operations 
entry   AH      2Fh 
return  ES:BX   address of DTA 
note 1) The DTA is set by function call 1Ah 
     2) Default DTA address is a 128 byte buffer at offset 80h in that program's 
	Program Segment Prefix