//编写函数，将一个数的指定位置置0或置1
#include <stdio.h>
unsigned int set_bit(unsigned int num, int pos, int flag)
{
	int n = 1;
	n = n << (pos - 1);    //将n的第pos位置1，其它全为0
	if (flag == 0)
	{
		num = num&(~n);
	}
	else if (flag == 1)
	{
		num = num | n;
	}
	else
		printf("flag error\n");
	return num;
}
int main()
{
	printf("%d\n", set_bit(3,1,0));     //2
	printf("%d\n", set_bit(4, 2, 1));   //6
	printf("%d\n", set_bit(15, 5, 1));  //31
	return 0;
}
<img src="http://img.blog.csdn.net/20150630155139259?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvZG91ZG91d2ExMjM0/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center"  />