Class-Responsibility-Collaboration card

Class-Responsibility-Collaboration cards (CRC cards) are a brainstorming tool used in the design of object-oriented software. They were proposed by Ward Cunningham. They are typically used when first determining which classes are needed and how they will interact.

CRC cards are usually created from index cards on which are written:

1. The class name.
2. The responsibilities of the class.
3. The names of other classes that the class will collaborate with to fulfill its responsibilities.

Using a small card keeps the complexity of the design at a minimum. It focuses the designer on the essentials of the class and prevents her from getting into its details and inner workings at a time when such detail is probably counter-productive. It also forces the designer to refrain from giving the class too many responsibilities.

External links

• A Laboratory For Teaching Object-Oriented Thinking, which provides an example of CRC cards in a model-view-controller paradigm.
• Using CRC Cards
• Introduction to CRC Cards
• Welcome to CRC cards