Learning C#

Your First Program: Hello World

In this chapter, you will create a very simple application that does nothing more than display the words “Hello World” to your monitor. This console application is the traditional first program for learning any new language; it demonstrates some of the basic elements of a C# program.

Once you write your “Hello World” program and compile it, this chapter will provide a line-by-line analysis of the source code. This analysis gives something of a preview of the language; Chapter 5 describes the fundamentals much more fully.

As explained earlier, you can create C# programs with any text editor. You can, for example, create each of the three programs shown previously (in Figures 2-1, 2-2, and 2-3) with Notepad. To demonstrate that this is possible, you’ll write your very first C# program using Notepad.

Begin by opening Notepad and typing in the program exactly as shown in Example 2-1.

Example 2-1. Hello World in Notepad

namespace NotePad
{
   class HelloWorld
   {
      // every console app starts with Main
      static void Main()
      {
         System.Console.WriteLine("Hello world!");
      }
   }
}

That is the entire program. Save it to your disk as a file called helloworld.cs.

We’ll examine this program in some detail in just a moment. First, however, it must be compiled.

The Compiler

Once you save your program to disk, you must compile the code to create your application. Compiling your source code means running a compiler and passing in the source code file. You run the compiler by ...