Function  1Ah   Set Disk Transfer Area Address (DTA)  
      Sets DTA address to the address specified in DS:DX 
entry   AH      1Ah 
	DS:DX   pointer to buffer 
return  none 
note 1) The default DTA is 128 bytes at offset 80h in the PSP. DOS uses the  
	DTA for all file I/O.  
     2) Registers are unchanged. 
     3) No error codes are returned. 
     2) Disk transfers cannot wrap around from the end of the segment to the  
	beginning or overflow into another segment.