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object-oriented programming


object-oriented programming

This chapter presented an overview of object-oriented programming languages. We discussed the heritage of Simula and the various areas of research and development the ideas introduced by Simula has generated.

The object paradigm


slide: Section 5.1: The object paradigm

An overview of existing object-oriented languages was given in section 1 and we noted the prominence of hybrid languages derived from Lisp and C.

Comparing Smalltalk, Eiffel, C++ and Java


  • criteria -- libraries, environments, language characteristics
  • comparison -- language characteristics

slide: Section 5.2: Comparing Smalltalk, Eiffel, C++ and Java

In section 2, we looked at a comparison of Smalltalk, Eiffel, C++ and Java, including criteria such as the availability of libraries, programming environments and language characteristics.

Design dimensions of object-oriented languages


  • {\em object-oriented} -- object-based + inheritance
  • orthogonal dimensions -- objects, types, delegation, abstraction
  • open systems -- dimensions of modularity

slide: Section 5.3: Design dimensions of object-oriented languages

In section 3, we discussed the design dimensions of object-oriented languages and characterized an orthogonal set of dimensions consisting of objects, types, delegation and abstraction. We also discussed the notion of open systems and multi-paradigm languages combining logic programming with object-oriented features.

Prototypes -- delegation versus inheritance


  • prototypes -- cloning and delegation
  • performance -- dynamic compilation

slide: Section 5.4: Prototypes -- delegation versus inheritance

In section 4, we dealt with classless prototype-based languages, supporting dynamic delegation instead of inheritance. We also discussed performance issues and observed that dynamic compilation based on runtime type information may achieve good results.

Meta-level architectures


  • class -- the concept of class
  • meta architecture -- subclass and instance hierarchy
  • reflection -- postulates

slide: Section 5.5: Meta-level architectures

Finally, in section 5, we reflected on the concept of class and discussed a reflective architecture unifying the interpretation of a class as an object, capable of answering messages, and as a description of the properties of its instances.

object-oriented programming


  1. What are the basic characteristics of object-oriented languages?
  2. How would you classify object-oriented languages? Name a few representatives of each category.
  3. What do you consider to be the major characteristic of the object model supported by C++? Explain.
  4. Why would you need friends?
  5. How would you characterize the difference between object-based and object-oriented?
  6. Along what orthogonal dimensions would you design an object-oriented language? Explain.
  7. Give a characterisation of active objects. In what situations may active objects be advantageous?
  8. How would you characterize prototype-based languages?
  9. What are the differences between inheritance and delegation? Does C++ support delegation? Explain. And Java?
  10. How would you characterize the concept of a class?
  11. Can you sketch the meta architecture of Smalltalk?
  12. How would you phrase the postulates underlying class-based languages? Can you give a reflective version of these postulates?

object-oriented programming

Further reading

A concise treatment of programming languages is given in  [BG94]. For a collection of papers on object-oriented concepts, see  [KL89]. Further, you may want to consult  [Wegner87], which contains the original presentation of the discussion concerning the distinction between {\em object-based} and {\em object-oriented}. Concurrency is studied in  [AWY93]. For Java, read the original white paper,  [Java]. An interesting extension of C++ is described in  [Petitpierre98]. At the corresponding web site, , there is much additional material. Finally, for an account of the design and evolution of C++, read  [Stroustrup97]. For more information on C++, visit , and for Java, .

(C) Æliens 04/09/2009

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