Most modern programming languages are class based, that is the code objects are object orientated and arranged into classes, methods and properties.
The nice thing about class based programming languages is that it's really easy to create high quality technical documentation from such languages. The documentation can simply show the hierarchy of classes used in the application, then list the sub-classes of each class. Finally the class's properties and methods can be described.
Modern object orientated (OO) programming languages that support the use of classes include Java and the .NET Framework (both Visual Basic.NET and C# support classes). A number of documentation tools for generating object orientated looking documentation exist for each of these programming languages - use the menu on the left of this page to find examples.