using System;
public class myCalc
{
   private int result;
   //constructor without a parameter defaults to 0
   public myCalc()
   {
      result = 0;
   }
   //constructor with parameter
   public myCalc(int x)
   {
      result = x;
   }
  //destructor
  ~myCalc()
  {
      result = 0;
  }
  //methods
  public void displayResult()
  {
     Console.WriteLine("Result = {0}", result);
  }
  public void add(int x)
  {
     result = result + x;
  }
  public void subtract(int x)
  {
     result = result - x;
  }
}

class myTest
{
   public static void Main()
   {
      myCalc mC = new myCalc(90);
      mC.displayResult();
      mC.add(45);
      mC.displayResult();
      mC.subtract(35);
      mC.displayResult();
      mC.subtract(110);
      mC.displayResult();
   }
}

///////////////////////////////////////////////
///////////////////////////////////////////////

Output
******
Result = 90
Result = 135
Result = 100
Result = -10