6 循环 ：计算 1/2+1/4+1/8+ .....

// 计算 1/2+1/4+1/8+ .....
#include <stdio.h>
main() {

    float n;
    float sum=0.0;
    float pow_2=1.0;     //需要专门用个变量放分母，因为分母要不断*2
    
    for (n = 1;n <= 10;n++) {
        pow_2 = 2 * pow_2;
        sum = sum + 1 / pow_2;
        printf("n=%.0f        sum=%f\n", n, sum);
    }


}