instance variable in c#

using instance constuctor we can intialize instance variable.

sample code:

public partial class EXPLAIN_PROGRAM_instance_variable : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        A a1 = new A(20);
        A a2 = new A(30);
        int r1 = a1.m();
        Response.Write(r1);
    }
}
public class A
{
    public int x;       //instance variable or global variable
    public A(int x)   //instance variable or instance method
    {
        this.x = x;
    }
    public int m()    // instance method
    {
        return x;
    }
}