Calcuate power n of x recursively

Given x and n, calculate its power n:

 1 int power(int x, int n)
 2 {
 3    if (n==0) 
 4      return 1;
 5    else (n%2==0) 
 6      return power(x*x, n/2);
 7    else 
 8      return x*power(x*x, n/2);
 9 }
10   
11