Function  21h  Random Read from File Specified by File Control Block     (FCB) 
     Reads one record as specified in the Struct -FCB into the current DTA.
entry   AH      21h 
	DS:DX	address of the opened Struct -FCB
return  AL      00h     successful read operation 
		01h     end of file (EOF), no data read 
		02h     DTA too small for the record size specified 
		03h     end of file (EOF), partial data read 
note 1) The current block and current record fields are set to agree with the 
	random record field. Then the record addressed by these fields is read 
	into memory at the current Disk Transfer Address. 
     2) The current file pointers are NOT incremented this function. 
     3) If the DTA is larger than the file, the file is padded to the requested 
	length with zeroes.