! sorting array elements
PROGRAM ex6_1

  IMPLICIT NONE
  INTEGER :: m, mark(100), n = 0, max, maxi, i, j

  DO WHILE( n <= 99 )
    PRINT '(1X, A)', 'Input integer, or negative one to stop: '
    READ *, m
    IF ( m <= 0 ) EXIT
    n = n + 1
    mark(n) = m
  END DO

  ! sorting
  DO i = 1, n - 1
    max = mark(i)
    maxi = i
    DO j = i+1, n
      IF ( mark(j) > max ) THEN
        max = mark(j)
        maxi = j
      END IF
    END DO
    IF ( maxi /= i ) THEN
      mark(maxi) = mark(i)
      mark(i) = max
    END IF
  END DO

  ! output
  DO i = 1, n
    PRINT '(1X, "rank", I3, " = ", I10)', i, mark(i)
  END DO

END PROGRAM ex6_1