Identifying Keywords The C# language reserves 77 identifiers for its own use, and you should not reuse these identifiers for your own purposes. These identifiers are called keywords, and each has a particular meaning. | Identifying Keywords The C language reserves 77 identifiers for its own use and you should not reuse these identifiers for your own purposes. These identifiers are called keywords and each has a particular meaning. Examples of keywords are class namespace and using. You ll learn the meaning of most of the keywords as you proceed through this book. The keywords are listed in the following table. abstract as base bool break byte case catch char checked class const continue decimal default delegate do double else enum event explicit extern false finally fixed float for foreach goto if implicit in int interface internal is lock long namespace new null object operator out override params private protected public readonly ref return sbyte sealed short sizeof stackalloc static string struct switch this throw true try typeof uint ulong unchecked unsafe ushort using virtual void volatile while TIP In the Visual Studio 2005 Code and Text Editor window keywords are colored blue when you type them. How Computer Memory is Organized Computers use memory to hold programs being executed and the data that these programs use. In order to understand the differences between value and reference types it is helpful to understand how data is organized in memory. Operating systems and runtimes such as the common language runtime frequently divide the memory used for holding data into two separate chunks each of which is managed in a distinct manner. These two chunks of memory are traditionally called the stack and the heap. The stack and the heap serve very different purposes When you call a method the memory required for its parameters and its local variables is always acquired from the stack. When the method finishes because it either returns or throws an exception the memory acquired for the parameters and local variables is automatically released back to the stack and is available for reuse when another method is called. When you create an object an instance of a class by using the .
