CSC2050 - Object-Oriented So ftware Engineering
Assessment

Sample Exam Questions

Instructions

For each question the number of marks is given.
Spend approximately 1 minute per mark.
This list of sample questions is not exhaustive. Make sure you revise all sections of the course.

Terms and Meanings

In point form summarize the significant differences between the object-oriented and procedural approaches to software development.
[5 marks]
Explain what is meant by object-oriented concept of "abstraction".
[2 marks]
Explain what is meant by object-oriented concept of "encapsulation".
[2 marks]
Define "polymorphism".
[2 marks]
Explain what is meant by the term "genericity".
[2 marks]
Explain the similarities and differences between the two forms of persistence: spatial and temporal.
[5 marks]
Explain what is meant by the term "software development model".
[5 marks]

Abstraction

Explain the difference between abstraction and encapsulation.
[5 marks]
What role(s) does abstraction play in object-oriented programming.
[5 marks]
What is the principal mechanism for abstraction in C++?
[3 marks]

Encapsulation

In point form, explain what benefits encapsulation brings to a language.
[8 marks]
What is the principal mechanism for encapsulation in C++?
[3 marks]
It is said that C++ does not strictly enforce encapsulation. In what way(s) is it possible to circumvent encapsulation in C++?
[8 marks]

Inheritance

List three reasons why it is useful to be able to inherit characteristics from parent classes.
[6 marks]
An inheritance hierarchy is sometimes described as a "directed acyclic graph". Why is this description appropriate?
[8 marks]
List the three different types of inheritance available in C++.
[3 marks]
It is sometimes more appropriate to aggregate (i.e. define) members rather than inherit them. Explain why. [Hint: consider a class implementing a car description and which members will be more appropriately defined, rather than inherited from the Vehicle base class].
[5 marks]
Explain how "multiple" inheritance differs from "single" inheritance.
[4 marks]
Give the declaration of a class D that publicly inherits from class B, and privately inherits from class C. (You may assume that class D has no additional members of its own).
[3 marks]

Genericity

List three possible advantages of using generic functions or classes.
[6 marks]
List three possible drawbacks of using generic functions or classes.
[6 marks]
If a C++ program defines both a non-generic and a generic version of a given function, which (if either) actually gets called?
[4 marks]
Suggest why it is appropriate that the C++ mechanism for genericity is called a "template".
[3 marks]
Explain how the concepts of genericity and function overloading are related.
[5 marks]

Polymorphism

List three advantages of using polymorphism in an object-oriented program.
[6 marks]
Explain briefly how a C++ program decides which virtual function to call during execution.
[8 marks]
The C programming language provide a construct which enables a primitive form of polymorphism. What is that construct?
[2 marks]

Function and operator overloading

Describe what is meant by the "signature" of an overloaded function, and explain why a functions signature must be unique, even if it's name is not.
[5 marks]
Explain how C++ manages to determine which version of an overloaded function to call.
[8 marks]

Explain the error in the following code:

		double max(double a, double b)
		{
			return a>b ? a : b;
		}

		double max(int a,int b)
		{	
			return a>b ? a : b;
		}

		int main(void)
		{
			cout << max(1,2.2);
		}

[3 marks]

List the advantages and drawbacks of the use of function overloading.
[5 marks]
Suggest two or more guidelines for when overloaded functions should and shouldn't be used.
[6 marks]
Explain why operator overloading is often not a good idea.
[5 marks]
List the three C++ operators which are most usually overloaded and explain why your answer to the previous question does not apply to these three operators.
[5 marks]
Write a overloaded operator function that allows the code:
```
		MyClass mc;
		cout << mc;
	
```
to behave identically to the code:
```
		MyClass mc;
		mc.PrintMeTo(cout);
	
```
[8 marks]

Modify the following class declaration:

		class String
		{
		public:
			String(void)
				: myStr(0) {}
			String(char* str)
				{ myStr = new char[strlen(str)];
				  strcpy(myStr,str);
				}
		private:
			char* myStr;
		};

so that the code:

		String s ("a string");
		s[1] = 'z';
		cout << s[1] << endl;

correctly allows access to individual characters in the string.

[8 marks]

Dymanically-allocated memory

Explain the diference between the new and new[] operators.
[4 marks]
Explain the diference between the delete and delete[] operators.
[4 marks]
Write a single C++ statement that dynamically allocates a single int and initializes it to 42.
[3 marks]
Write one or more C++ statements that dynamically allocates an array of 42 ints and initializes each one to zero.
[3 marks]

Constructors and destructors

Write a declaration for a constructor for the class Annotation. Your constructor should take two arguments: number (of type int), and ref (of type TextRef).
[2 marks]

Modify the following class declaration:

		class String
		{
		public:
			String(void)
				: myStr(0) {}
			String(char* str)
				{ myStr = new char[strlen(str)];
				  strcpy(myStr,str);
				}
		private:
			char* myStr;
		};

by adding a suitable destructor.

[5 marks]

Modify the String class from the previous question by adding a copy constructor.
[5 marks]

Miscellaneous C++ syntax

Write a declaration for an enumerated type called Hombre, with values good, bad, and ugly.
[2 marks]

Class members

Explain why it is almost always a bad idea to declare the data members of a class to be public.
[5 marks]

List the

semantic differences between this version of the Value::Negate() member function:

		void Value::Negate(void)
		{
			this->myVal *= -1;
		}

and this one:

		void Value::Negate()
		{
			myVal = -myVal;
		}

[3 marks]

What is the minimum number of data members a class may have?
[2 marks]
What is the minimum number of function members a class may have?
[2 marks]

Exceptions

Briefly explain how exceptions work in C++.
[8 marks]
Under what circumstances is it useful to catch exceptions by value?
[4 marks]
Under what circumstances is it useful to catch exceptions by reference or pointer?
[4 marks]
Rewrite the following function so that any exceptions which are thrown by the functions set(), game(), and match() are caught within the function play(). Your code should print a message ("exception caught") and then call exit() if any exception is thrown.
```
		Score play(void)
		{
			Score s;
			while (!match())
			{
				while (!game())
				{
					s = set();
				}
			}
			return s;
		}
	
```
[8 marks]

The software development process

Briefly outline the various stages of the Waterfall model.
[3 marks]
Explain why the Waterfall model is not a satisfactory model of real-world software development.
[5 marks]
In point form, describe the Fountain model of software development.
[3 marks]
Draw a labeled diagram explaining Boehm's spiral model of software development.
[6 marks]
List three or more properties which increase as the radius of the spiral model increases, and explain why they increase.
[4 marks]
List two or more properties which decrease as the radius of the spiral model increases, and explain why they decrease.
[4 marks]
The Spiral model covers a greater range of activities than the Fountain model. Explain which sector(s) of the Spiral model correspond to stages in the Fountain model.
[5 marks]
Define "rapid prototyping" and explain how it fits into the Exploratory Programming model of software development.
[6 marks]
Explain what is meant by saying that "software development models are just theories".
[6 marks]

Metrics

Suggest why persuasiveness is a characteristic of a good metric.
[5 marks]
Suggest why it is desireable that software metrics be programming language independent.
[5 marks]
Give two examples of non-computable metrics, and explain why such metrics are of limited value.
[5 marks]
List four quantities related to software development which can be easily measured.
[4 marks]
List four quantities related to software development which cannot be easily measured.
[4 marks]
Explain why the "lines-of-code" metric is a poor one.
[5 marks]

Compute the cyclomatic complexity of the following program:

		int globalVal = 0;

		int main(void)
		{
			while (globalval<10)
			{
				if (globalval < 2)
				{
					globalval *= 2;
				}
				else if (globalval > 8)
				{
					globalval -= 2;
				}
				else
				{
					globalval = 10-globalval;
				}
			}
			for (int i=0; i<globalval; i++)
			{
				cout << i << endl;
			}
		}

Show all your working.

[8 marks]

Compute the cyclomatic complexity of the following code fragment:

		int x = 10;
		do
		{
			double y;
			if (cin >> y)
			{
				if (y!=0) 
				{
					for (i=1; i<y; i++)
					{
						cout << i*x/y << endl;
					}
				}
			}
		}
		while (x-->0);

Show all your working.

[8 marks]

Compute the cyclomatic complexity of the following function:
```
		template <class TYPE>
		TYPE max(TYPE a, TYPE b)
		{
			return (a>b) ? a : b;
		}
	
```
Show all your working.
[8 marks]

Classification

In point form, explain the difference between classical (Platonic) classification and a priori clustering.
[5 marks]
Why can prototype-based classification be described as "instance-outward"?
[4 marks]
Prototype-based classification uses "paradigms". In this context what is a "paradigm".
[4 marks]
Give an overview of how you might use an analogicial approach to clustering to create a software system which controls Internet traffic. [hint: think of how road traffic is controlled]
[8 marks]

Object-oriented design

List the five main steps in an object-oriented design process.
[5 marks]
Describe how the "informal description" technique may be used to identify the objects, methods, and classes in a problem.
[5 marks]
Explain the role of experts in Domain Analysis.
[4 marks]
When performing Domain Analysis, why is it important not to automatically accept participants' explanations of their behaviour.
[5 marks]
At the highest level, objects may fulfil one of three roles. List those roles and describe the characteristics of objects in each of those roles.
[10 marks]
Explain the difference between the datum role and the data type role.
[6 marks]
List the four commonest relationships which may exist between two classes.
[4 marks]
Explain how a C++ program can specify that two classes are in an "is implemented as a" relationship.
[3 marks]
Explain what is meant when we say that "the interesting behaviour of an object-oriented system is (often) emergent"?
[8 marks]

Draw an interaction diagram corresponding to the execution of the following program:

		class Base
		{
		public:
			virtual void PrintMe(void)
			{
				cout << "Base!" << endl;
			}
		};

		class Derived
		{
		public:
			virtual void PrintMe(void)
			{
				Base::PrintMe();
				cout << "Derived!" << endl;
			}
		};

		int main(void)
		{
			Base b;
			Derived d;

			b.PrintMe();
			d.PrintMe();
		}

[8 marks]

Draw a class hierarchy diagram (in Booch notation) for a system to solve the following problem. Do not write any text descriptions or code.
The El Cheapo video store needs a computerized database system to record borrowed videos, CDs, and video games. Videos are categorized as new release, weekly, or five-for-five-dollars. video games may be either PlayStation, MegaDrive, or Saturn.

El Cheapo need to be able to check whether an individual item is currently on loan, when it is due back, how much is owing on it (if it is overdue), as well as details of who borrowed it (i.e. name, address, phone number, licence number).

They also need to be able to generate lists of items selected by various criteria: item type, items currently in, items currently out, most popular, least recently borrowed. This lists must be able to be sorted alphabetically and by video ID number.

They also want to generate lists of customers secting by various criteria: most prolific borrowers, inactive (no borrowing for a month or more), who owes the most on overdue books.
[20 marks]
Draw a class hierarchy diagram (in Booch notation) for a system to solve the following problem. Do not write any text descriptions or code.
We are creating a symbolic mathematics package. We want to be able to specify functions of X, Y, and Z. Each function will consist of a left- and right-hand expression, and each expression will consist of one or more terms, with addition or subtraction operators between them.

Each term may be either a constant (a numerical value or the special constant C) or a product (a numerical coefficient followed by one ore more of the variables X, Y, and Z, each raised to some power).

The mathematics package will be able to perform the following operations on a function:
[20 marks]

Last updated: Fri Sep 25 08:19:08 1998