August 1997 OP216: Object Oriented Programming (Question 5) Suggested Solutions

5.	(a) Discuss any three benefits of object-oriented programming and give appropriate examples to illustrate the benefits.		[12]
	You should structure your answer as follows: list each benefit, discuss that benefit in more detail, and give an appropriate example. Do this for each of the three benefits.
	The answer must cover the following aspects.
		Encapsulation: grouping of essential characteristics or information hiding. A data structure along with its primitive operations can be encapsulated within a single abstraction. It is a technique for hiding information within a structure, such as the hiding of instance data within a class. For example, a stack could be implemented by a fixed length array whose publicly available functions would be push and pop.	[4]
		Inheritance: The property of objects by which instances of a class can have access to data and method definitions contained in a previously defined class.
		Classes can be organised into a hierarchy. Thus, reducing the interdependency among software components and encouraging the development of re-useable software components. For example, a ball class can inherit from the sphere class.	[4]
		Polymorphism: allows the same function name or operator to be executed by arguments of a variety of types.
		It is made possible by the overloading of function names in which two or more procedure bodies are known by the same name in a given context, and are disambiguated by the type and number of parameters supplied.	[4]

	(b) State and explain one disadvantage of object-oriented approaches to programming.		[3]
	Object oriented programming languages are harder to implement efficiently.		[1]
	This is because the compiled code needs to carry out more checks at runtime than normal imperative languages, like Pascal.		[1]
	Consequently, the code is longer and runs slower.		[1]
	[3 marks]

	(c) Provide concise answers to the following questions:
		(i) Can a non object-oriented language be used to create and use ADTs? Explain your answer.	[3]
		Yes.	[1]
		object oriented programming is just a paradigm or a methodology	[1]
		An ADT can be implemented using a non OOP language by hard-coding it.	[1]
		(ii) Why do object-oriented languages exist?	[1]
		Object oriented programming languages developed as they allowed a much clearer way of representing complex systems. Consequently, they can make (certain kinds of) coding easier.	[1]
		(iii) Name three OOP languages.	[1]
		SmallTalk, Simula, Java, Objective C, ADA-95, CLOS, C++	[1]
	[5 marks]