Thread: Problem with assigning value to array elements

Hi, I'm new to this site and programming as a whole, but since I'll be starting college this fall as comp sci major I thought I'll start to learn c++ by myself. I have MS Visual C++ 6 and I was looking through the tutorial included with it. I got to arrays and thought I'll try writing a very simple program with some stuff I've learned, but I ran into a problem. Here's the code.

Code:

//Finding exponents of 2 with array
#include <iostream>
#include <iomanip>
using namespace std;

int main()

{	
	int exponent;						//declare int variable exponent
	cout << "What would you like to raise 2 to? \n";	//ask for user input	
	cin >> exponent;					//user input 'exponent'
	int power[exponent+1];				//declare array 'power' with 'exponent+1' elements	
									      //so index will be from 0 to 'exponent number'
	power[0] = 1;						//assign power[0] as 1 since 2^0 = 1										
	int i = 1;								//i is counter
	
	do									//loop to assign values to array power
	{
		power[i] = power[i-1]*2;		//each element value in array is 2 times the value before it
		++i;							//increment counter by one
	} while (i <= exponent);			//repeats until i reaches exponent			

	for(i=0; i<=exponent; i++)			//loop to display each value in the array
	{
		cout << "2 to the " << i;
		if (i=1)
			cout << "st";
		else if (i=2)
			cout << "nd";
		else if (i=3)
			cout << "rd";
		else
			cout << "th";
		cout << " power is " << power[i] << ". \n";
	}
	return 0;
}

These are the error messages when I try to compile.

D:\Program Files\Microsoft Visual Studio\MyProjects\learn\learn.cpp(12) : error C2057: expected constant expression
D:\Program Files\Microsoft Visual Studio\MyProjects\learn\learn.cpp(12) : error C2466: cannot allocate an array of constant size 0
D:\Program Files\Microsoft Visual Studio\MyProjects\learn\learn.cpp(12) : error C2133: 'power' : unknown size
Error executing cl.exe.

I assume the errors say the array has unspecified size, but wouldn't [exponent+1] specify it according to user input?
Please explain what the problem is, sorry if my code looks bad, but I've only just started learning >_<.
Thanks!