INT 21,27 - Random Block Read Using FCB

	AH = 27h
	CX = number of records to read
	DS:DX = pointer to an opened FCB

	on return:
	AL = 00 if read was successful
	   = 01 if EOF (no data read)
	   = 02 if DTA is too small
	   = 03 if EOF (partial record read)
	CX = actual number of records read

	- allows random access and sequential reading of a group
	  of records from a file opened with an FCB into the DTA
	- FCB must be setup with drive id, filename, extension
	  record length and random record number before call