Function  45h   Duplicate a File Handle (DUP) 
entry   AH      45h 
	BX      file handle to duplicate 
return  CF      clear   AX      duplicate handle 
		set     AX      error code  (4, 6) 
note 1) If you move the pointed of one handle, the pointer of the other will  
	also be moved. 
     2) The handle in BX must be open