Ch 2 - unable to find function runhelloworld

Hi, just got the book and got to chapter two after i built my .cs file for hello world, i get the .cs file to exec in the console but when i type runhelloworld(); as the book says, i get a message saying, unable to find function runhelloworld. i have also tried helloworld, hello, world, functionrunhelloworld, etc. nothing is seeming to work. any help would be greatly appreciated, here is my .cs file code.

// ========================================================================
// HelloWorld.cs
//
// This module is a program that prints a simple greeting on the screen.
//
// ========================================================================

function hello()
// ----------------------------------------------------
// Entry point for the program.
// ----------------------------------------------------
{
echo("Hello World");
}