Which of the following statements are correct?

1. An argument passed to a ref parameter need not be initialized first.
2. Variables passed as out arguments need to be initialized prior to being passed.
3. Argument that uses params keyword must be the last argument of variable argument list of a method.
4. Pass by reference eliminates the overhead of copying large data items.
5. To use a ref parameter only the calling method must explicitly use the ref keyword.

namespace CuriousTabConsoleApplication
{ 
    class SampleProgram
    {
        static void Main(string[] args)
        { 
            int num = 1;
            funcv(num); 
            Console.Write(num + ", "); 
            funcr(ref num); 
            Console.Write(num + ", ");
        }
        static void funcv(int num)
        { 
            num = num + 10; Console.Write(num + ", ");
        }
        static void funcr (ref int num)
        { 
            num = num + 10; Console.Write(num + ", ");
        } 
    } 
}

1. If we do not return a value from a subroutine then a value -1 gets returned.
2. Subroutine definitions cannot be nested.
3. Subroutine can be called recursively.
4. To return the control from middle of a subroutine exit subroutine should be used.
5. Subroutine calls can be nested.

namespace CuriousTabConsoleApplication
{
    class SampleProgram
    {
        static void Main(string[ ] args)
        {
            int i = 10;
            double d = 34.340;
            fun(i);
            fun(d);
        }
        static void fun(double d)
        {
            Console.WriteLine(d + " ");
        }
    }
}

1. C# allows a function to have arguments with default values.
2. C# allows a function to have variable number of arguments.
3. Omitting the return value type in method definition results into an exception.
4. Redefining a method parameter in the method's body causes an exception.
5. params is used to specify the syntax for a function with variable number of arguments.

1. A function cannot be called from a subroutine.
2. The ref keyword causes arguments to be passed by reference.
3. While using ref keyword any changes made to the parameter in the method will be reflected in that variable when control passes back to the calling method.
4. A subroutine cannot be called from a function.
5. Functions and subroutines can be called recursively.

namespace CuriousTabConsoleApplication
{
    class Sample
    { 
        public static void fun1()
        { 
            Console.WriteLine("CuriousTab1 method");
        }
        public void fun2()
        { 
            fun1(); 
            Console.WriteLine("CuriousTab2 method");
        }
        public void fun2(int i)
        { 
            Console.WriteLine(i);
            fun2(); 
        } 
    } 
    class MyProgram
    { 
        static void Main(string[ ] args)
        { 
            Sample s = new Sample(); 
            Sample.fun1(); 
            s.fun2(123);
        } 
    } 
}

Tab1 method 
123
Tabl method 
Tab2 method

Tab1 method 
123
Tab2 method

Tab2 method 
123
Tab2 method 
Tabl method

Tabl method
123

Tab2 method 
123
Tabl method

namespace CuriousTabConsoleApplication
{ 
    class Sample
    { 
        static Sample()
        { 
            Console.Write("Sample class ");
        }
        public static void CuriousTab1()
        { 
            Console.Write("CuriousTab1 method ");
        } 
    } 
    class MyProgram
    { 
        static void Main(string[ ] args)
        { 
            Sample.CuriousTab1();
        } 
    } 
}

Sample s1 = new Sample(); 
Sample s2 = new Sample(9, 5.6f);

public Sample()
{
    i = 0; 
    j = 0.0f;
}
public Sample (int ii, Single jj)
{
    i = ii;
    j = jj;
}

public Sample (Optional int ii = 0, Optional Single jj = 0.0f)
{
    i = ii;
    j = jj;
}

public Sample (int ii, Single jj)
{
    i = ii;
    j = jj;
}

Sample s;

s = new Sample();

class Sample
{
    int i;
    Single j;
    double k;
    public Sample (int ii, Single jj, double kk)
    {
        i = ii;
        j = jj;
        k = kk;
    } 
}