//Tells the complier that this program uses types from the System namespace.using System; //Declares a new namespace, called HelloWorld //A namespace is a set of type declarations associated with a name.namespace HelloWorld {    //Declares a new class type, called Program    class Program    {        //Declares a method called Main as a member of class Program        //Main is a special function used by the complier as the starting point of the program.        static void Main(string[] args)        {            //Contains only a single, simple statement; this line constitutes the body of Main.            //Simple statements are terminated by a semicolon.            //This statement uses a class called Console, in namespace System, to print out the message to a window on the screen            //Without the using statement in line 1, the compiler wouldn't have known where to look for class Console.            Console.WriteLine("Hello World!");        }    }}