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Wednesday, 22 August 2012

Basic OOP program

Object Oriented Programming or OOP is an approach to programming(in general) that is based on the view of treating each entity or element as an object, in such a way that each object is unaware of the existence of other objects. Before going further, let me lay out some basic details for you.

CLASS -  Many of you must have the definition of class as : "a class is the collection of data members of same or different type, grouped under a common name". Well this is actually a very trivial definition of class. A class serves as a blueprint for building something. Simply put, it is a layout that describes where everything should be put together. In programming
terminology, a class is a way of binding the data describing an entity and its associated functions together.

Now i can go on and on, about classes and object, why the use of classes, data abstraction and so on, but all that you can find in any textbook. Let us jump to the practical implementation of OOP.

The article follows a program that demonstrates the use of classes and objects. Before i get into the nitty gritty of it all, please understand that you need to focus on the concept , not the
technical details. The "TECH DETAILS" will come with time and practice. Focus must be on understanding the concept. So let's begin :

The following program creates a class "MarkSheet" with a single member variable "marks" of type int(a.k.a integer). Now the class also has two PUBLIC member functions, a setter function and a corresponding getter function. Getter and Setter functions are not some SPECIAL functions, they are just named that way, sort of a trend. The job of a "getter" function is to return
the value of a variable of the class and the job of a "setter" function is to SET the value of a variable of the class.

For e.g : here is a demo setter function

void setDAY(int x) // sets the value of 'day' with the value contained by 'x'
     day = x;

Similarly, e.g : here is a demo getter function

int getDay() // 'gets' or returns the value of the variable 'day'
     return day;

The class has the following setter and getter functions :
1 - setMarks() // sets the marks of the student
2 - getMarks() // gets or returns the marks of the student

In the main() function, two objects,name objA and objB are declared that represent object of student A and B respectively. The program then prompts the user to enter the values
of the marks of students A and B. The marks are set by using the setMarks() setter function. After that, the marks are displayed by calling the getMarks() getter function.

Note : Please do not get into the details of using 'this'. Just understand that 'this' acts as a pointer to the current object. To get more details on the use of 'this' in OOPS, please refer
the FAQ.

// C++ program to demonstrate the concept of Object Oriented Programming Structure(OOPS)


using namespace std;

class MarkSheet
     int marks;

     public :

     void setMarks(int marks) // setter function
          this->marks = marks;

     int getMarks() // getter function
          return this->marks;

}; // end of class MarkSheet

int main()
     MarkSheet objA; // object A of class MarkSheet
     MarkSheet objB; // object B of class MarkSheet
     int temp;

     // propmts the user to enter the marks of student A
     cout<<" Enter the marks of student A : ";
     objA.setMarks(temp); // uses the setter function to set the marks of student A

     // propmts user to enter the marks of student B
     cout<<" Enter the marks of student B : ";
     objB.setMarks(temp); // uses the setter function to set the marks of student B

     cout<<"\n ---------- Marks of A and B are as follows ------------ \n";
     cout<<" Marks of student A : "<<objA.getMarks(); // displays the marks of student A
     cout<<"\n Marks of student B : "<<objB.getMarks(); // displays the marks of student B
     return 0;
}// end of main

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

------ OUTPUT -----