%  cat -n sample1.c
	     1	int sub(a,b)
	     2	
	     3	int a,b;
	     4	{
	     5		return a*b;
	     6	}
	     7	
	     8	main()
	     9	{
	    10		int i,j;
	    11		for(i=0;i>10;i++){
	    12			j=2*i;
	    13			printf("%d\n",sub(i,j));
	    14		}
	    15		exit(0);
	    16	}

	% cflow sample.c
	  1 main: int(), 
	  2 sub: int(), 
	  3 printf: <>

	% cflow -r sample.c
	  1 main: int(), 
	  2 printf: <>
	  3 main : <>
	  4 sub: int(), 
	  5 main : 3