INT 21,1B - Get Allocation Table Information

	AH = 1B

	on return:
	AL = sectors per cluster
	CX = bytes per sector
	DX = clusters on disk
	DS:BX = pointer to Media Descriptor Byte found in FAT

	- retrieves information on capacity and format of default drive
	- DS:BX can be used to determine if drive is RAMDISK or removable
	- see  INT 21,1C