C++ Function Definition raise number to a power

#include <iostream>
using namespace std;
double power( double n, int p=2);   //p has default value 2
int main()/*  w  w  w .  j  a va2 s  .  co  m*/
{
   double number, answer;
   int pow;
   char yeserno;
   cout << "\nEnter number: ";      //get number
   cin >> number;
   cout << "Want to enter a power (y/n)? ";
   cin >> yeserno;
   if( yeserno == 'y' )             //user wants a non-2 power?
   {
      cout << "Enter power: ";
      cin >> pow;
      answer = power(number, pow);  //raise number to pow
   }
   else
      answer = power(number);       //square the number
   cout << "Answer is " << answer << endl;
   return 0;
}
// returns number n raised to a power p
double power( double n, int p )
   {
      double result = 1.0;             //start with 1
      for(int j=0; j<p; j++)           //multiply by n
         result *= n;                  //p times
      return result;
}