Data Design - Data Structures - Lecture Slides, Slides of Data Structures and Algorithms

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Chapter 2 Data Design and Implementation

• Lecture

Data Abstraction

• Separation of a data type ’ s logical properties from its implementation

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LOGICAL PROPERTIES IMPLEMENTATION

What are the possible values? How can this be done in C++?

What operations will be needed? How can data types be used?

APPLICATION

0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1

REPRESENTATION

Data Encapsulation

• is the separation of the representation of data from the applications that use the data at a logical level; - a programming language feature that enforces information hiding

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int y;

y = 25;

Abstract Data Type (ADT)

• A data type whose properties (domain and

operations) are specified independently of any particular implementation.

Collection ordered in different ways

Communication between the Application Level and Implementation Level

Viewing a library from 3 different levels

• Application (or user) level: Library of Congress, or Baltimore County Public Library.
• Logical (or ADT) level: domain is a collection of books; - operations include: check book out, check book in, pay fine, reserve a book.
• Implementation level: representation of the structure to hold the “ books ” , and the coding for operations.

4 Basic Kinds of ADT Operations

• Constructor -- creates a new instance (object) of an

ADT.

• Transformer -- changes the state of one or more of

the data values of an instance.

• Observer -- allows us to observe the state of one or

more of the data values without changing them.

• Iterator -- allows us to process all the components in

a data structure sequentially.

Two Forms of Composite Data Types

UNSTRUCTURED

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Components are not organized with respect to one another.

The organization determines method used to access individual data components.

STRUCTURED

EXAMPLES: EXAMPLES: arrays classes and structs

Records

A record is a composite data type made up of a finite collection of not necessarily homogeneous elements called members or fields****. For example...

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.year 2008

.maker ‘ h ’‘ o ’‘ n ’‘ d’ ‘ a’ ‘ \0 ’...

.price 18678.

thisCar at Base Address 6000

struct CarType

struct CarType {

int year; char maker[10]; float price;

} ;

CarType thisCar; //CarType variable s CarType myCar;

Valid struct operations

• Operations valid on an entire struct type variable:

assignment to another struct variable of same type,

pass as a parameter to a function (either by value or by reference),

return as the value of a function.

Pass-by-value

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CALLING BLOCK

FUNCTION CALLED

sends a copy of the contents of the actual parameter

SO, the actual parameter cannot be changed by the function.