Department of Computer Engineering Faculty of Engineering, Prince of Songkla University 1 5 – Abstract Data Types

2 Overview: 1.What is Data Abstraction? What is ADT? 2.Model for an Abstract Data Type 3.Complex Number ADT Example 4.How Well are ADTs Supported in C? 5.C++ 6.ADT vs Object-Oriented Programming

3 1.1 What is Data Abstraction? Concept of “Abstraction” Allows us to consider the high-level characteristics of something without getting bogged down in the details For example: Process abstraction in procedural programming like C, we can use (pre-defined) functions without concern how they really works inside. Data Abstraction We know what a data type can do How it is done is hidden

4 1.2 What is an Abstract Data Type? Abstract Data Type (ADT) Defines a particular data structure in terms of data and operations Offers an interface of the objects (instances of an ADT) An ADT consists of Declaration of data Declaration of operations Encapsulation of data and operations : data is hidden from user and can be manipulated only by means of operations

5 1.3 ADT Implementation Implementaion of an Abstract Data Type (ADT) Hidden from the user Same ADT may be implemented in different ways in different languages Some languages offer built-in ADTs and/or features to be used to implement ADTs (user-define types) ADTs support modular design which is very important in software development

6 2.1 Model for an ADT Interface - Operations Data Structure System design with ADTs Problem definiton Identification of ADTs (identify data or attributes) Specify ADT operationsSpecify ADT interactions Implement ADTs Identify object hierarchy (if using OOP)

7 2.2 Clients and Manufacturers implementation interface ADT manufacturer’s responsibility client use

8 2.3 Benefits Manufacturer Benefits: easy to modify, maintain profitable reusable Client Benefits: simple to use, understand familiar cheap component–based

9 3. Complex Number ADT Example A complex number has a real part and an imaginary part. e.g.: 2+4i Interface (operations) ? create a complex number add, subtract, multiply, divide print a complex number test to see if something is complex etc.

10 Declare a complex number Interface: Complex c1, c2, c3; Possible Implementation (in C language ): struct complex { double real,imag; } typedef struct complex Complex;

11 Create a complex number Interface: c1 = create_complex(2, 3); /* conceptually, c1 = 2+3i */

12 Implementation: Complex create_complex(double real, double imag) { Complex c; c.real = real; c.imag = imag; return c; }

13 Add two complex numbers Interface: c3 = add_complex(c1, c2); /* conceptually, c3 = c1 + c2 */

14 Implementation: Complex add_complx(Complex c1, Complex c2) { Complex csum; csum.real = c1.real + c2.real; csum.imag = c1.imag + c2.imag; return csum; }

15 Using the Complex Number ADT #include /* type implementation */ struct complex { double real,imag; typedef struct complex Complex; /* operation interface */ Complex create_complex(double,double); Complex add_complex(Complex, Complex); /* other Complex prototypes print_complex()... */ continued

16 int main ( ) { Complex c1, c2, c3; c1 = create_complex(2,-3); c2 = create_complex(2,-3); c3 = add_complex(c1,c2); print_complex(c3); return 0; } /*Implementation of Complex functions */ : Using the Complex Number ADT

17 4. How Well are ADTs Supported in C? Does C enforce the use of the ADTs interface and the hiding of its implementation? No

18 5. C++ and OOP C++ is a superset of C, which has added features to support object oriented programming (OOP) C++ offers STL (Standard Templates Library) providing a set generic data structures which allow programmers to easily implement standard data structures like queues, lists, and stacks. C++ supports classes things very like ADTs Other OOP languages such as Java, Smalltalk

19 6. ADT vs Object-Oriented Programming (OOP) ADTs are not a part of a particular programming language Rather they are implemented by a programmer to solve a particular problem or some class of problems In OOP, an ADT can be easily modeled as a class An instance as an object Data of ADT as properties or fields of a class Operations as methods ADT ≠ OOP Classes in OOP offers more features than ADTs : Inheritance (Superclass-Subclass), Polymorphisms, etc.