Classes

To facilitate dealing with the hundreds or even thousands of different software objects that can exist in an application system, objects are organized into classes. A class is a group of objects that have a common data structure and that all use the same methods. This means that the data structure can be defined for the class. Each object within the class has a unique set of data values that correspond to the class structure. It also means that the methods are defined once at the class level and are used by each of the objects of the class.

Example:   A banking application will require many individual accounts. Each account will have data associated with it, for example account-balance and date-opened. Each account will have methods that allow other parts of the application to access an individual account such as deposit, withdraw and current-balance. The checking account class defines the data layout and methods for all of the individual checking accounts, thus they all work in the same way and serve the same purpose.