[面向对象] block到底有什么作用，请大家来举例

SUBROUTINE swap(i, j) 
  INTEGER :: i, j 
  IF (i < j) 
    ! The BLOCK statement has no BLOCK_construct_name. The corrsponding END BLOCK 
    ! statement cannot have a BLOCK_construct_name either.
    BLOCK                  
      INTEGER :: temp
      temp = i 
      i = j 
      j = temp 
    END BLOCK         
  END IF              
END SUBROUTINE swap

program a

  INTEGER :: i = 5, j = 7 ,temp = 33
  write(*,*) temp,i,j
    BLOCK                  
      INTEGER :: temp
      temp = i 
      i = j 
      j = temp 
      write(*,*) temp , i , j
    END BLOCK         
  write(*,*) temp , i , j     
end program a