Define:

Without violating encapsulation, capture and externalize an object's internal state allowing the object to be restored to this state later. Yes No N/A

Usage:

For rollback undo

Provide access to object internal state without violating encapsulation.

Structure:

In the memento pattern the is the originator the object we wish to track the memento the object that holds its state and the caretaker that maintains the memento.

Example:

A simple wpf drawing application with undo feature.