Introduction to Object oriented Programming basics
- 1. UNIT II Object based Programming
- 2. Procedural Programming ◦sequence of things ◦Emphasis is on doing things i.e. procedures. ◦share global data ◦top-down approach Modular Programming ◦Emphasizes separating the functionality ◦modules perform logically discrete functions. ◦no interaction between modules. ◦Each module works independently Generic Programming ◦Generic programming is about generalizing software components. ◦Algorithms are written in terms of to-be-specified-later. ◦In C++ class and function templates are particularly effective mechanisms.
- 3. Object-Oriented Programming ◦decomposition of problem into a number of entities called objec ◦Emphasis is on data rather than procedure ?? ◦Objects have attributes and can take actions ◦pass messages to objects, so that they take action ◦The same message works differently for various objects ◦A method can work appropriately with different types of data ◦Objects can inherit traits of previously created objects ◦Information hiding is more complete than in procedural program ◦New data and functions can be added easily whenever necessar ◦Follows bottom-up approach
- 4. Top Down approach Identify the goal or problem: The goal or problem needs to be clearly identified and measurable. Break it down into sub-goals: The sub-goals/sub-problems are what the top-up approach i all about. Solve each sub-goal/sub-problem: Using the same top-up approach, the sub-problems/sub- goals/problems are broken down into smaller manageable parts. Repeat steps 2 and 3 until the overall goal/problems are
- 5. Bottom-Up Approach Identify the components or tasks: The components or tasks need to be clearly identified and measurable. Build the system or solution: The system or solution gets its name from the fact that it is built from the individual components/tasks. Test: The system/solution needs to be tested to meet the requirements. This can be done by running a series of tests on the system/solution. Repeat steps 2 and 3: This may involve several iterations of the bottom-up
- 6. Limitations of procedural programming ◦Difficult to relate with real world objects ◦Abstraction and modularization is difficult ◦Difficult to understand ◦Difficult to maintain Need of object-oriented programming ◦Possible to map objects in the problem domain ◦Data Hiding : Security ◦ Inheritance : Eliminate redundancy , reusability ◦Its flexibility ◦ It makes the coding more organized ◦Simple maintenance, an advanced analysis of complicated programs
- 7. Structured Vs OOP Structured OOP Focuses on Process Focuses on Object Follows Top Down Approach Follows Bottom Up Approach
- 8. Fundamentals of object-oriented programming ◦ objects ◦ classes ◦ data members ◦ methods ◦ messages ◦ data encapsulation ◦ data abstraction and information hiding ◦ inheritance ◦ polymorphism
- 9. Object ◦Objects are basic run time entities. ◦ e.g. person, a place, a bank account, or any item that the program has to handle. ◦Each object take up space in the memory to store data and code. ◦OOP encapsulates data (attributes) and functions (behavior) into packages called objects. Objects have the property of information hiding. ◦Representation of object
- 10. ◦Objects Interact with each other by sending messages to each other.
- 11. Message Passing
- 12. • Class ◦A class is a blueprint or prototype that defines the data members and the methods (functions) common to all objects of a certain kind. ◦Objects (data and functions) are members of user-defined types called classes. ◦A class definition is an extension of a C structure definition , made up of declarations of variables and of function ◦The variables are typically declared to be private or protected and the functions are typically declared to be public. ◦structures members are public by default and class members are private by default.
- 13. Example : Objects and Classes Rima R002 Rita R003 Bina R004 Rani R001 class object class Student char name int rollNo setName() setRollNo() calcMarks()
- 14. Program is composed of a collection of individual units or objects, as opposed to a traditional view in which a program is a list of instructions to the computer. Data variable Member Function Data variable Member Function Data variable Member Function Object A Object B Object C
- 15. • Data members ◦Attributes of object. ◦The variables are typically declared to be private or protected • Methods or member functions or messages ◦Functions operate on class data. ◦ functions are typically declared to be public. ◦Defined outside or inside class. ◦Objects communicate with each other. Encapsulation ◦The process of binding code and data together in the form of a capsule ◦Data is not accessible to the outside world, only those function which are wrapped in the class can access it. ◦Since the classes use the concept of data abstraction, they are known as Abstract Data Type(ADT). ◦EXAMPLE-tv Data Abstraction or Data Hiding ◦The process of extracting the essential information and hiding the irrelevant details
- 16. Inheritance ◦The feature by which one class acquires the properties and functionalities of another class ◦Classes are extensible ◦You can create new classes that extend or are descendents of existing classes ◦The descendent classes can inherit all the attributes of the parent class ◦Hierarchical classification ◦Reusability
- 17. Inheritance
- 18. “Person” is a generalization of “Student”. “Student” is a specialization of “Person”. Person Name Gender Age Student Reg. No. Course Marks Teaching Staff Qualification Designation Specialization
Editor's Notes
- #3: 2. The main aim of OOP is to bind together the data and the functions that operate on them so that no other part of the code can access this data except that function. Passing messages Message passing is similar to the idea of sending and receiving messages in real life. Suppose we are at a hotel and we want to order room service. For this, we write a message (place an order) to the room service department and put it in the internal messaging system of the hotel. Here message contains details about what we want and our room number. Similarly in OOP, one object can send a message to another object (room service department) with specific data (order details). Then other object performs the requested action based on the information provided in the message. Polymorphism is the core concept of the object-oriented programming language that allows programmers to build logical codes. In this concept of OOP, programmers can access objects of different types through the same interface where each type provides its own implementation of the interface
- #4: In this approach, each function in a code is unique and works independently of other functions. The top-down approach is heavily used in the C programming language. Specification tends to change over time and in a top-down approach, all decisions made from the beginning of the project depend directly or indirectly on the high-level specification. In Dynamic Programming, the top-down approach is slow as compared to the bottom-up approach, as it involves recursion. There is a chance of stack overflow here. It takes more memory space as it involves recursion.
- #6: POP has two major drawbacks, viz. (1) data move freely around the program and are therefore vulnerable to ranges caused by any function in the program, and (2) it does not model very well the real-world problems. GROUPINGOF SIMILAR OBJECTS int.o a class
- #10: In OOPS, objects are self-sufficient units that possess their own data and behaviour. Suppose one object (Sender) wants to communicate with another object (Receiver) to access data or carry out an action by calling its methods. For this, Sender will send a message to Receiver and then Receiver will perform the desired action or returns the requested data. Message passing provides an interface between objects and helps them to communicate in a loosely coupled way while keeping their inner complexities hidden. In Java, we implement message passing using method calls. For example, when Object A invokes a public method of Object B, it is sending a message to Object B. Note that Object A can only invoke Object B's public methods, not its private methods.
- #16: Inheritance is one of the key features of Object-oriented programming in C++. It allows us to create a new class (derived class) from an existing class (base class). The derived class inherits the features from the base class and can have additional features of its own.
- #17: class Animal { // eat() function // sleep() function }; class Dog : public Animal { // bark() function };