FILE-CONTROL.
   SELECT SEQUENTIAL-FILE ASSIGN TO 'A:\SEQ.DAT'
      ORGANIZATION IS LINE SEQUENTIAL.
   SELECT INDEXED-FILE
      ASSIGN TO 'A:\INDMAST.DAT'
      ORGANIZATION IS INDEXED
      ASSESS IS SEQUENTIAL
      RECORD KEY IS IND-SOC-SEC-NUM
      FILE STATUS IS INDEXED-STATUS-BYTES.
      
FILE SECTION.
FD SEQUENTIAL FILE
   RECORD COTNAINS 39 CHARACTERS
   DATA RECORD IS SEQUENTIAL-RECORD.
01 SEQUENTIAL-RECORD.
	05 SEQ-SOC-SEC-NUM 			PIC X(9).
	05 SEQ-REST-OF-RECORD		PIC X(30).

FD INDEXED-FILE
	RECORD CONTAINS 39 CHARACTERS
	DATA RECORD IS INDEXED-RECORD.
01  INDEXED-RECORD.
	05 IND-SOC-SEC-NUM  		PIC X(9).
	05 IND-REST-OF-RECORD		PIC X(30).
	
PROCEDURE DIVISION.
0010-UPDATE-MASTER-FILE.
	OPEN INPUT SEQUENTIAL-FILE
		OUTPUT INDEXED-FILE.
	PERFROM UNTIL END-OF-FILE-SWITCH = 'YES'
		READ SEQUENTIAL-FILE
			AT END
				MOVE 'YES' TO END-OF-FILE-SWITCH
			NOT AT END
				MOVE SEQ-SOC-SEC-NUM TO IND-SOC-SEC-NUM
				MOVE SEQ-REST-OF-RECORD TO IND-REST-OF-RECORD
				WRITE INDEXED-RECORD
					INVALID KEY PERFORM 0020-EXPLAIN-WRITE-ERROR
				END-WRITE
		END-READ
	END-PERFORM.
	CLOSE SEQUENTIAL-FILE
			INDEXED-FILE.