C++ constructors

#include<iostream>
#include<stdio.h>
#include<conio.h>

using namespace std;


class integer
{
	private:
		int i;
	
	public:
		
		void getdata()
		{
			cout<<endl<<"Enter an integer";
			cin>>i;
		}
		
		void setdata(int j)
		{
		i=j;
		}
		
		integer(){ //zero argument constructor
		}
		
		integer(int j) //one argument constructor
			{
				i=j;
			}
			
		void displaydata()
			{
				cout<<endl<<"value of i is : "<<i<<endl;
			}
		
}

void main()
	 {
	 	integer i1(100),i2,i3;
	 	i1.displaydata();
	 	i2.setdata(200);
	 	i2.displaydata();
	 	i3.getdata();
	 	i3.displaydata();
	 getch();
	 }