While循环

        int a=5,count=0;
	while(--a) count++;
	printf("a is%d   count is%d\n",a,count);

 结果：

            a is 0  count is 4

        int a=5,count=0;
	while(a--) count++;
	printf("a is%d   count is%d\n",a,count);

 结果：

            a is -1  count is 5