Function 02h	Read Sectors - read one or more sectors from diskette
entry   AH      02h 
	AL      number of sectors to read  
	BX      address of buffer (ES=segment) 
	CH      track number (0-39 or 0-79 for floppies) 
		(for hard disk, bits 8,9 in high bits of CL) 
	CL      sector number (1 to 18, not value checked) 
	DH      head number (0 or 1) 
	DL      drive (0=A, 1=B, etc.) (bit 7=0)  (drive 0-7) 
	ES:BX   address to store/fetch data  (buffer to fill) 
       [0000:0078]  dword pointer to diskette parms 
return  CF      clear (0) for successful 
		set (1) failure 
		AH      status (00h, 02h, 03h, 04h, 08h, 09h, 10h, 0Ah, 20h, 
			40h, 80h) 
	AL      number of sectors transferred 
note 1) Number of sectors begins with 1, not 0 
     2) Trying to read zero sectors is considered a programming error; results 
	are not defined