打开/关闭位的操作

#include <stdio.h>
#include<math.h>

/* 当flag为1时把第n位的0变为1 */
/* 当flag为0时把第n位的1变为0 */
/* 假设n从右侧开始，最右边第一位是1 */
void setBit(unsigned* pData, unsigned n, unsigned flag){
	unsigned m;
	if(flag == 0){
		m = pow(2, 32) - 1 - pow(2, n - 1);
		*pData &= m;
	}
	else{
		m = pow(2, n - 1);//m = 4即0100
		*pData |= m;//1010 | 0100 = 1110
	}
}

int main(){
	unsigned data = 10;//1010

	unsigned n = 2;//把第二位1变为0，输出8
	//unsigned n = 3;//把第三位0变为1,输出14

	unsigned flag = 0;//flag为0把1变为0
	//unsigned flag = 1;//flag为1,把0变为1

	setBit(&data, 2, 0);
	printf("%d\n", data);

	return 0;
}