OOP in C++

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For the students of FYBSc (IT), SYBSc (CS), SYBCA


  • C++ allows specifying more than one definition for an operator in the same scope, which is called operator overloading respectively.
  • When to call an overloaded operator, the compiler determines the most appropriate definition to use by comparing the argument types used to call the function or operator with the parameter types specified in the definitions. The process of selecting the most appropriate overloaded operator is called overload resolution.
  • Overload most of the built-in operators available in C++ and thus a programmer can use operators with user-defined types as well.
  • Overloaded operators are functions with special names the keyword operator followed by the symbol for the operator being defined. Like any other function, an overloaded operator has a return type and a parameter list.

Boxoperator+ (constBox&);

  • The above code declares the addition operator that can be used to add two Box objects and returns final Box object. Most overloaded operators may be defined as ordinary non-member functions or as class member functions. In case we define above function as non-member function of a class then we would have to pass two arguments for each operand as follows:

Boxoperator+ (constBox&,constBox&);

  • Following is the example to show the concept of operator over loading using a member function. Here an object is passed as an argument whose properties will be accessed using this object, the object which will call this operator can be accessed using this operator as explained below:

#include <iostream.h>
#include <conio.h>
class Box
{ public:
double getVolume(void)
return length * breadth * height; }
void setLength( double len )
{ length = len; }
void setBreadth( double bre )
{ breadth = bre; }
void setHeight( double hei )
{ height = hei; }

// Overload + operator to add two Box objects.
Box operator+(const Box& b)
{ Box box;
box.length = this->length + b.length;
box.breadth = this->breadth + b.breadth;
box.height = this->height + b.height;
return box; }
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box};

void main( )
Box Box1; // Declare Box1 of type Box
Box Box2; // Declare Box2 of type Box
Box Box3; // Declare Box3 of type Box
double volume = 0.0; // Store the volume of a box here

// box 1 specification

// box 2 specification

// volume of box 1
volume = Box1.getVolume();
cout << “Volume of Box1 : ” << volume <<endl;

// volume of box 2
volume = Box2.getVolume();
cout << “Volume of Box2 : ” << volume <<endl;
// Add two object as follows:
Box3 = Box1 + Box2;

// volume of box 3
volume = Box3.getVolume();
cout << “Volume of Box3 : ” << volume <<endl;


When the above code is compiled and executed, it produces the following result:

Volume ofBox1:210

Volume ofBox2:1560

Volume ofBox3:5400

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