C Illustrates file I/O

C Created:  Joe Zachary, November 13, 1992
C Modified:

      PROGRAM FILE2

      IMPLICIT NONE
      INTEGER SUM, NUMBER, ERROR

      SUM = 0

      OPEN(UNIT=7, FILE='filename', STATUS='OLD')

      ERROR = 0
      DO WHILE (.TRUE.) 
         READ (UNIT=7, FMT=*, IOSTAT=ERROR) NUMBER
         IF (ERROR .LT. 0) THEN
            PRINT *, 'The sum is ', SUM
            STOP
         ELSE IF (ERROR .GT. 0) THEN
            PRINT *, 'Bad input encountered in the file!'
         ELSE
            SUM = SUM + NUMBER
         ENDIF
      ENDDO
      
      END