CSC/ECE 517 Fall 2007/wiki2 5 as

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CRC cards

    CRC cards. Hundreds of Web pages cover CRC cards. Which explain them best? Which explain them in the context of specific languages, e.g., Ruby and Java? Which exercises can be used to teach them best, (i) interactively over the Web, (ii) to a class of students, via in-class exercises, (iii) for self-study?


Introduction to CRC


    CRC – Class, Responsibility, Collaborators cards were introduced to teach the concepts of Object Oriented Programming to a procedural programmer. The model was proposed by Kent Beck and Ward Cunningham in there paper “A Laboratory for Teaching Object-Oriented Thinking” released in OOPSLA ’89. It is now used to develop object-oriented models. The cards are written based on the system requirements which define the behavior of the system. This model contains a set of index cards which is divided into three sections –

  • Class – It is a collection of similar objects. This section appears on the top of the CRC card and is a singular noun or singular noun phrase.
  • Responsibility – section appears below the class name and gives a bulleted list of the actions which the class is capable of. It identifies the problems that can be solved. This is expressed by active verbs.
  • Collaborators – These are the collection of classes with whom the class interacts to complete its actions.


    • The following are the links that can be used to understand what CRC cards are and how they work. These links give a view about certain aspects of CRC. http://c2.com/doc/oopsla89/paper.html - “A Laboratory For Teaching Object-Oriented Thinking” paper by Kent Beck and Ward Cunningham can be found in this link. This link gives a detail explanation about why CRC cards were introduced. http://www.agilemodeling.com/artifacts/crcModel.htm - This link provides description about CRC models and an example to create CRC cards. http://www.uow.edu.au/~nabg/PwithC/C11.html - gives a detailed description OO development from Analysis to Implementation. http://c2.com/doc/crc/draw.html - CRC description of a drawing editor called HotDraw which was written in SmallTalk by Ward Cunningham and Kent Beck. CRC for O-o languages Ruby: Java: SmallTalk: http://www.d.umn.edu/~gshute/ood/accounts/home.html - The CRC model and SmallTalk code for a Bank Account application CRC Exercises i) Interactive over Web http://dshaw.com/3x5s/ - Interactive CRC cards that can be edited and saved online during a CRC session. There are few commercial products like WinTranslator (http://www.excelsoftware.com/wintranslator.html) available for creating CRC cards.

    ii) For a class of students via in-class exercises http://64.233.169.104/search?q=cache:ji81-0SXBcsJ:www.cs.iastate.edu/~cs362/handouts/crc-tutorial.pdf - gives a step by step procedure on how to execute CRC sessions in class.

    iii) Self-Study http://www.csc.calpoly.edu/~dbutler/tutorials/winter96/crc_b/ - tutorial for self-study http://www.cs.gordon.edu/courses/cs211/ATMExample/CRCCards.html - an example of CRC card for ATM application There are a few books available that gives complete description about CRC cards. The CRC card book (http://www.amazon.com/Card-Book-Addison-Wesley-Object-Technology/dp/product-description/0201895358 ) provides solutions to software design problems using CRC cards. Implementation examples in languages like C++, Java and SmallTalk is also provided.

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