The type System.Char (a struct) contains a number of useful methods, and a couple of constants.
Locate the type System.Char in your C# documentation and take a look at the methods available on characters.
You may ask where you find the C# documentation. There are several possibilities. You can find it at the Microsoft MSDN web site at msdn.microsoft.com. It is also integrated in Visual Studio and - to some degree - in Visual C# express. It comes with the C# SDK, as a separate browser. It is also part of the documentation web pages that comes with Mono. If you are a Windows user I will recommend the Windows SDK Documentation Browser which is bundled with the C# SDK.
Along the line of the character demo program above, write a small C# program that uses the char predicates IsDigit, IsPunctuation, and IsSeparator.
It may be useful to find the code position - also known as the code point - of a character. As an example, the code position of 'A' is 65. Is there a method in System.Char which gives access to this information? If not, can you find another way to find the code position of a character?
Be sure to understand the semantics (meaning) of the method GetNumericValue in type Char.