INT 21,14 - Sequential Read Using FCB

	AH = 14h
	DS:DX = pointer to an opened FCB

	on return:
	AL = 00 if successful read
	   = 01 if end of file (no data read)
	   = 02 if DTA is too small
	   = 03 if end of file or partial record read

	- reads a record from file pointed to by FCB at the location
	  specified in current block and current record number
	- data record is read into the DTA
	- FCB record number is updated