[Note: Much of the C# language enables the programmer to specify declarative information about the entities defined in the program. For example, the accessibility of a method in a class is specified by decorating it with the method-modifiers public, protected, internal, and private. end note] C# enables programmers to invent new kinds of declarative information, called attributes. Programmers can then attach attributes to various program entities, and retrieve attribute information in a run-time environment. [Note: For instance, a framework might define a HelpAttribute attribute that can be placed on certain program elements (such as classes and methods) to provide a mapping from those program elements to their documentation. end note] Attributes are defined through the declaration of attribute classes (24.1), which may have positional and named parameters (24.1.2). Attributes are attached to entities in a C# program using attribute specifications (24.2), and can be retrieved at run-time as attribute instances (24.3).