static void Main(string[] args)
        {
            computer comp1 = new computer("Dell", "Usa");
            laptop   lap1  = new laptop("Dell", "Usa", "Inspirion", "Red");
            desktop  desk1 = new desktop("Dell", "USA", "FOLL", "Blue");

            Console.WriteLine(comp1.ToString());
            Console.WriteLine(lap1.ToString());
            Console.WriteLine(desk1.ToString());
            Console.ReadLine();
        }
        static void Main(string[] args)
        {
            computer comp1 = new computer("Dell", "Usa");
            Laptop   lap1  = new Laptop("Dell", "USA", "Inspiron", "Blue");
            Desktop  desk1 = new Desktop("Dell", "USA", "XPS", "Red");

            Console.WriteLine(comp1.Format());
            Console.WriteLine(lap1.FormatLaptop());
            Console.WriteLine(desk1.FormatDesk());
            Console.ReadLine();
        }