CS2006 - Data Structures I Chapter 2 Principles of Programming & Software Engineering.

CS2006 - Data Structures I

Chapter 2Principles of Programming

& Software Engineering

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Topics

Modular Design Concepts Abstraction OO Design

Encapsulation Inheritance Polymorphism

Top Down Design Structure Chart

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Abstraction & Information Hiding Example: Cars brakes

Clientbox

Car Black box

Push the brakes

My interior design isusing

Cylinder brakes or

Drum brakes

Brake pedal pushed

Car stop

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Abstraction Abstraction separates the purpose of a

module from its implementation. Example: Sorting

Clientbox

SortBlack box

Sort this data please,

I don’t care how you do it

I can sort data intoascending order without

you knowing how

Unsorted data

Sorted data

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Procedural Abstraction Procedural Abstraction is the process of

separating the purpose of a method from its implementation.

Once written the method can be used without any knowledge of how it is implemented - only need to know the parameters.

Example: nearly all methods in the entire Java API.

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Abstract Data Types ADT - a collection of data along with a set of

operations that can be performed on that data.

No details about how the data is stored or how the operations on the data are implemented.

An ADT is a general description of the design of a module with no details.

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Abstract Data Types Data Structure - the implementation of an

ADT in a programming language. The details of data storage and how

operations are performed are crucial parts of a data structure.

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ADT List Any List in general will allow the following

operations: Create an empty list Destroy a list Determine whether a list is empty Determine the number of items in a list Insert an item at a given position in the list What else?

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Object-Oriented Design Three elements to OOD:

Encapsulation - combining data and operations within one object.

Inheritance - objects can inherit data and/or methods from other objects.

Polymorphism - objects can determine operations at execution time.

Every object knows its "true" type regardless of type casting

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Inheritance A class can inherit the variables and methods of another

class. It can keep those it wants and replace those it doesn’t.

Example: our Person class. we want a class of students. we can’t change our Person class because

many people are using it as it stands perhaps we don’t have access to the source code

Create a new class called Student that extends the current class Person by the addition of a new variables and methods

Person

Student

parent classsuper class

child classsubclass

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FacultyStudent

Person

Class design extend the definition of Person

build a subclass for each specific type of person

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FacultyStudent

Person

Class hierarchyint getAge()

String getName()

float getGPA()

void setId(String new_id) void setSalary(float newSalary)

float getHoursWorked()

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Object-Oriented Design Produce a collection of objects that have

behaviours How to do

Identifying the objects in the problem UML Contents of Software Engineering (cosc 4506)

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Object-Oriented Design Consider the nouns and verbs in the

problem domainCreate a ATM machine which allow user to retrieve,

deposit, transfer and check balance of their accounts

ATMAccount: account

Open ()Close()

Account

Type: StringAmount: double

transfer (int )checkBalance()

retrievedeposit ()

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Top-Down Design Is a structured programming methodology Focused on algorithm design.

Goal is to break a large problem into a set of smaller problems that are more easily solved.

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Top-Down Design An attempt is made to solve a problem in

terms of small subproblems Divide and Conquer strategy

How?

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Top-Down Design (TDD)

Structure chart:Find Median

Get middle scoreSort scoresRead Scores

Read scoreFrom user

Insert scoreinto array

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Structure Charts

Can add some info into our structure chart to show how we share the data

Two type of info that get passed between our methods Data Control Information or flags

Thing like “perform such and such an operation” Or “ we have hit the end of file”

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Structure Charts

Use named arrows to show the data flow Data arrows

Flag arrows

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Structure Charts

Structure chart:Find Median


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Structure Charts Structure chart:

Find Median


Read score Insert scoreinto array MarkEnrty: contain score and ID

MarkArray: contain array of scores

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Find Median


Read score Insert scoreinto array

EOFMarkEntry MarkEntry

MarkEnrty: contain score and IDMarkArray: contain array of scores

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Find Median





MarkArray

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Find Median





MarkArray MarkArrayMarkArray

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Structure Charts

The manner in which this structure diagram would be implemented as a program is obvious

It is now possible to create a skeletal program with all the method headers All you need is to fill in detail

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Structure Charts

Public class FindMedian {public static void main (..) {

}public static void readScore (int []MarkArray) { }public static void sortScore (int []MarkArray) {}public static int getMedian (int []MarkArray) {}

}

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Structure Charts

public class FindMedian {

public static void main (..) {int MarkArray [];


}

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Structure Chartspublic class FindMedian {

public static void main (..) {int MarkArray [];readScore (MarkArray);


}

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public static void main (..) {int MarkArray [];readScore (MarkArray);sortScore (MarkArray);


}

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public static void main (..) {int MarkArray [];readScore (MarkArray);sortScore (MarkArray);getMedian (MarkArray);

}public static void readScore (int []MarkArray) { }public static void sortScore (int []MarkArray) {}public static void getMedian (int []MarkArray) {}

}

CS2006 - Data Structures I Chapter 2 Principles of Programming & Software Engineering.

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