二分法实现数字的开方运算

今天闲着，听了mit的计算机编程课程后，写了一个实现开平方的算法，主要也体现了二分法的思想，每次迭代让问题规模减半.
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
using namespace std;
int main(){
double a = 8.0;
int c = 1000;
double low = 0.1;
double high = 10.0;
double guess = (low+high)/2;
while(c>=0&&fabs(guess*guess-a)>0.001){
if(guess*guess<a)
{
low = guess;
}
else
{
high = guess;
}
guess = (low+high)/2;
c--;
}
printf("%f\n",guess);
printf("%d\n",c);
return 1;
}