Function 04h	Verify - verify that a write operation was successful
entry   AH      04h 
	AL      number of sectors to verify (1-8) 
	CH      track number  (for hard disk, bits 8,9 in high bits of CL) 
	CL      beginning sector number 
	DH      head number 
	DL      drive number (0-7) 
return  CF      set on error 
		AH      status (see above)  
	AL      number of sectors verified