CrcCard''''''s were originally introduced as a technique for teaching object-oriented concepts; they have also been successfully used as a full-fledged modeling technique. Scott W. Ambler feels that CRC models are an incredibly effective tool for conceptual modeling as well as for detailed design. CRC cards feature prominently in ExtremeProgramming (XP) (Beck 2000) as a design technique. See also AgileDevelopment.

A Class Responsibility Collaborator (CRC) model (KentBeck & WardCunningham 1989; Wilkinson 1995; ScottAmbler 1998a) is a collection of standard index cards that have been divided into three sections. A class represents a collection of similar objects, a responsibility is something that a class knows or does, and a collaborator is another class that a class interacts with to fulfill its responsibilities.