A function returns a value, whereas a subroutine cannot return a value.

static void fun(object i)
{ ... }

static void fun(int i)
{ ... }

static void fun(double i, int j)
{ ... }

static void fun(int i, double j)
{ ... }

static void fun(int i, double j, )
{ ... }

namespace CuriousTabConsoleApplication
{
    class SampleProgram
    {
        static void Main(string[ ] args)
        {
            int i;
            int res = fun(out i);
            Console.WriteLine(res);
        }
        static int fun (out int i)
        {
            int s = 1;
            i = 7;
            for(int j = 1; j <= i; j++)
            {
                s = s * j;
            }
            return s;
        } 
    } 
}

namespace CuriousTabConsoleApplication
{
    class SampleProgram
    {
        static void Main(string[ ] args)
        {
            object[] o = new object[] {"1", 4.0, "India", 'B'};
            fun (o);
        }
        static void fun (params object[] obj)
        {
            for (int i = 0; i < obj.Length-1; i++)
            Console.Write(obj[i] + " ");
        }
    }
}

namespace CuriousTabConsoleApplication
{ 
    class SampleProgram
    { 
        static void Main(string[ ] args)
        { 
            int a = 5;
            int s = 0, c = 0; 
            s, c = fun(a); 
            Console.WriteLine(s +" " + c) ;
        }
        static int fun(int x)
        {
            int ss, cc;
            ss = x * x; cc = x * x * x; 
            return ss, cc;
        } 
    } 
}

1. An error will be reported in the statement s, c = fun(a); since multiple values returned from a function cannot be collected in this manner.
2. It will output 25 125.
3. It will output 25 0.
4. It will output 0 125.
5. An error will be reported in the statement return ss, cc; since a function cannot return multiple values.

namespace CuriousTabConsoleApplication
{
    class SampleProgram
    {
        static void Main(string[ ] args)
        {
            int i = 5;
            int j;
            fun1(ref i);
            fun2(out j);
            Console.WriteLine(i + ", " + j);
        }
        static void funl(ref int x)
        {
            x = x * x;
        }
        static void fun2(out int x)
        {
            x = 6; 
            x = x * x; 
        }
    }
}

namespace CuriousTabConsoleApplication
{ 
    class SampleProgram
    { 
        static void Main(string[] args)
        { 
            int[]arr = newint[]{ 1, 2, 3, 4, 5 }; 
            fun(ref arr);
        }
        static void fun(ref int[] a)
        { 
            for (int i = 0; i < a.Length; i++)
            { 
                a[i] = a[i] * 5; 
                Console.Write(a[ i ] + " "); 
            } 
        } 
    } 
}