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AUT University

406704: Program Design and Construction

Mock Exam Paper

October 2010

Read these instructions first:

This is a 2 hour paper.

It has 100 marks.

This is a closed bookexam. You may not refer to reference materials or use a mobile phone or

computer. You will not need a calculator. You must not confer with your fellow students.

The exam is divided into two parts. Part A consists of short-answer questions. Part B consists of

longer questions requiring you to design software. Each part carries 50 marks.

Answerall questions in Part A.

Attempt 2 questions from Part B. If you attempt more than 2 questions, all of your answers will be

marked and your best two marks taken.

Read all questions first. Plan how you will spend your time. You have a little over a minute to

spend on each mark. If you do not know the answer to a question, complete other questions first

then come back to it. Allow adequate time for completing Part B, where the questions are longer

and carry more marks.

You may answer the questions in any order. Clearly indicate the number of the question being

answered in you answer book.

Large amounts of text are not required in answers. Use short sentences, lists, and simple

diagrams.

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Part A - This section consists of short answer questions testing your knowledge and understanding

of program design and construction.

1. Software development projects often look like a race to develop a computer program before

the money available to do so runs out.

a. [1 mark] What would a company usually expect to spend the most money on whendeveloping software?

b. [4 marks] Give two examples a software engineering techniques or technologies and for

each say how it helps to reduce costs.

2. In the course of developing a computer program we make a number of decisions about what

to do with our code.

a. [3 marks] Bad decisions, or 'mistakes' can end up costing us money and threatening the

success of our project. List two factors that are important in determining how expensive a

mistake ends up being, and what kinds of software engineering techniques help us reducethese costs?

b. [2 marks] There is a cost associated with making good decisions too, because we have to

spend time and effort doing so. But sometimes this cost is unnecessary. Why, and what

kinds of software engineering techniques help us reduce these costs?

3. Your software development project uses a version control system.

a. [1 mark] what does a version control system do?

b. [2 marks] list two routine activities involved in working with a version control system

c. [2 marks] Identify two advantages to using a version control system.

4. Here is some code that

a. [3 marks] Write a Java expression that will evaluate to true if all of the preconditions for

this code are met.

b. [2 marks] Write a Java expression that evaluates to true if the function x() does what we

would expect from its name, and false otherwise.

5. a. [2 marks] Explain what is wrong with the following function for printing a countdown.

b. [3 marks] Rewrite the function so that it works as expected without using recursion.

6. Functional decomposition breaks complex tasks down into smaller ones. Often this

corresponds to the structure of a procedural program. Suppose we have a function

printPartyInvitation() that takes the name and address of one of our friends, and creates a

letter inviting that friend to a party.

a. [3 marks] If printPartyInvitation() calls three subroutines to get its job done, and those

subroutines have good names that reflect their function, what might they be called?

b. [2 marks] Choose one of your subroutines from the previous answer, and suggest two

further subroutines that it might call.

7. a. [4 marks] Java provides some standard exceptions that should be thrown when a method

receives a parameter value that it cannot handle. Name two, and describe precisely whenthey should be thrown.

b. [1 mark] When will the following piece of code not generate an AssertionError if its line

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is reached in an executing Java program?

8. a. [1 mark] Give the Java code for initialising a reference variable with a new object of type

java.lang.Object.

b. [2 marks] How does inheritance reduce the cost of programming in an object-oriented

language?

c. [2 marks] How does encapsulation reduce the cost of programming in an object-orientedlanguage?

9. a. [5 marks] The documentation of a design pattern is usually separated into a number of

short sections, each of which gives some useful information about the pattern. Name five of

these sections.

b. [5 marks] Describe a design pattern that you know.

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Part B - This part consists of four programming questions. Attempt at least two.

10. [25 marks] Convert the following structured program into a procedural program. Obey the

following style guide:

1. All variables and procedures should have meaningful names

2. No procedure should contain more than one level of nesting in its structure

3. Procedures can only share information via parameters and return values (you cannotassume a variable is shared by two subroutines

4. Avoid duplicate code

System.out.println("Welcome to the romance compatibility checker!");

System.out.print("Enter your name: ");

Scanner scanner = new Scanner(System.in);

String a = scanner.next();

float t1 = 0;

for(int n = 0; n < a.length(); n++) {

int v = a.charAt(n) - 'a';

t1 += v;

}

t1 = t1/a.length();

boolean y = true;

while(y) {

System.out.print("Enter the name of your friend: ");

String b = scanner.next();

float t2 = 0;

for(int n = 0; n < b.length(); n++) {

int v = b.charAt(n) - 'a';

t2 += v;

}

t2 = t2/b.length();

float d = t1 - t2;

if(d < -5) System.out.println("No, you are too good for them!");

elseif(d > 5) System.out.println("No, they are too good for you!");

else System.out.println("Good match! You will be very happy!");

System.out.print("Check another name? (y/n): ");

String r = scanner.next();

y = r.equalsIgnoreCase("y");

}

System.out.println("Goodbye!");

13. [25 marks] A self-service supermarket checkout has a touchscreen to interact with the user.Write three user stories for the system. One user story should cover the whole process of

checking out. Two more should cover smaller parts of the process in more detail.

For each story, list the user decisions made in the story. For each decision list the

information that the user needs to make the decision. Group the decisions into tasks and

design task windows for each task. Sketch each window, and indicate the features that make

it easy for the customer to use.

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14. [25 marks] An 'outline editor' is a text editor that allows documents to be arranged into

sections. A section has a title and can contain paragraphs of text, and other sections. A

document is a section with no parent.

Using a boxes and lines diagram (or UML class diagrams if you are familiar with them),

sketch the design of an outline editor that uses the Model/View/Controller architecture.

Show in the diagram the structure of the classes making up the model. Annotate yourdiagram to show where particular design patterns are used. Include additional design

patterns in your architecture if they would add useful functionality.

15. [25 marks] Show how you would use test-first programming to develop a procedure to

convert an integer representing the time in minutes since midnight to a string in 24 hours

format hh:mm. Lay out your answer as follows: first write an assertion statement that tests

the procedure (you don't need to show a whole JUnit test method); then show the procedure

that you would write to make the assertion pass; then write another assertion; then show

what the procedure would look like after you have changed it to make both previous

assertions pass. Continue like this until you think you have enough tests and a correct

implementation. Remember to always produce the least amount of code that will make theprior tests pass.