C# For Beginners Lesson 8 - Simple Program: Print a line of Text

The canonical "hello, world" program can be written as follows:

using System;
class Hello
{
   static void Main() {
      Console.WriteLine("hello, world");
   }
}

The source code for a C# program is typically stored in one or more text files with a file extension of .cs, as in hello.cs. Using the command-line compiler provided with Visual Studio .NET, such a program can be compiled with the command-line directive

csc hello.cs

which produces an application named hello.exe. The output produced by this application when it is run is:

hello, world

Close examination of this program is illuminating:

• The using System; directive references a namespace called System that is provided by the Microsoft .NET Framework class library. This namespace contains the Console class referred to in the Main method. Namespaces provide a hierarchical means of organizing the elements of one or more programs. A "using" directive enables unqualified use of the types that are members of the namespace. The "hello, world" program uses Console.WriteLine as shorthand for System.Console.WriteLine.
• The Main method is a member of the class Hello. It has the static modifier, and so it is a method on the class Hello rather than on instances of this class.
• The entry point for an application — the method that is called to begin execution — is always a static method named Main.
• The "hello, world" output is produced using a class library. The language does not itself provide a class library. Instead, it uses a class library that is also used by Visual Basic .NET and Visual C++ .NET.