how to change from for loop to while loop

[vanessa93]

#include<iostream>
using namespace std;
int main()
{
int length;

cout << "Enter the length of the hollow square\n";
cin>>length;
for(int i=0; i<length; i++)
{
for(int j=0; j<length; j++)
{
if(i==0 || i==length-1 || j==0 || j==length-1)
cout << "*";
else
cout << " ";

}
cout<<endl;
}
}

[tipaye]

#include <iostream>

using namespace std;

int main()
{
	int length = 10;
	int i;

	for (i = 0; i < length; ++i) {
		cout << i << endl;
	}

	cout << endl << endl;

	i = 0;
	while (i < length) {
		cout << i << endl;
		++i;
	}
}