Function 18h	Set Media Type For Format  (diskette)	     (AT, XT/286, PS/2)
entry   AH      18h 
	CH      lower 8 bits of number of tracks 
	CL      high 2 bits of number of tracks (6,7) sectors per track  
		(bits 0-5) 
	DL      drive number 
return  AH      00h      if requested combination supported 
		01h      if function not available 
		0Ch      if not suppported or drive type unknown 
		80h      if there is no media in the drive 
	ES:DI   pointer to 11-byte parameter table