A class defines the abstract characteristics of a thing (object), including its characteristics and what it can do.
From a programming point of view a class can be described as a template from which direct instances are generated.
When a class is declared, the declaration includes its members, which describe its characteristics. Members of a class can be categorised as follows:
| data member | constant | constant value associated with the class |
| field | variable of the class | |
| function member * | method | implements the computations and actions that can be performed by the class |
| property | named characteristic associated with reading and writing that characteristic. | |
| event | notification that can be generated by the class | |
| constructor | implements actions required to initialise instances of the class | |
| destructor | implements actions to be performed before instances of the class are permanently discarded | |
| nested type | type that is local to the class |
| * | Members that can contain executable code are collectively known as the function members of the class. |
From the perspective of users of classes in some programming languages, such as C++, properties can be used in the same way as data members, and data members and properties can be grouped into a single properties category, so that members are categorised simply as properties, methods and events as follows:
| property | constant |
| field | |
| property | |
| method | method |
| constructor | |
| destructor | |
| event | event |
| example | Java |
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