Function 03h	Write Sectors - write from memory to disk
entry   AH      03h 
	AL      number of sectors to write (1-8) 
	CH      track number (for hard disk, bits 8,9 in high bits of CL) 
	CL      beginning sector number 
		(if hard disk, high two bits are high bits of track #) 
	DH      head number 
	DL      drive number (0-7) 
	ES:BX   address of buffer for data 
return  CF      set if error 
		AH      status (see above) 
	AL      number of sectors written 
note 1) Number of sectors begins with 1, not 0 
     2) Trying to write zero sectors is considered a programming error; results 
	are not defined