using a function in a loop

[Kreadeth]

Hi! I am an beginner c++ programmer. Today I was writing some small program that gets a number and tell you how many digits it has. First of all, I defined a function for raising a number to a definite power. I wrote this:

 int power(int x, int y)
{
int i;
int result = 1;

while (i < y)
{
result *= x;
i++;
}

return result;
}

I know now what was wrong with it. In the line three I hadn't set a value for i. So adding one to it and comparing it to y was absurd. But it worked! So I didn't noticed my mistake and keeped on:

int main ()
{
int a;
int b;
int i=-1;
cin >> a;

while (b != 0)
{
i++;
b = a / power (10,i);
}

cout << i;

return 0;
}

When I executed this and gave it a number greater than 9, it would go in a vicious circle. After a lot of struggling with its code I noticed that mentioned mistake and corrected it(By giving it the initial value of 0) and the code worked! But I can not get it. Why is that? Why despite my mistake the function worked, but when I decided to use it in a loop, it went screwed?

I am not a native speaker, so pardon any probable grammatical mistake. Thanks a lot.

[shadowCODE]

Firstly, cmath has a std::pow.

Calling the function power(a,b) works even with the error. Most often will return 1 because i uninitialized will have value greater than y.

There is an infinite loop in main because the value of b does not change.
b = a / 1 and will remain a.

[Kreadeth]

I used GNU GCC compiler in Code::Blocks. when I try the codes in another compiler it doesn't go well. I don't know why is that. Anyway. Thank you!