Example : A simple C++ program to show constructor concept.
#include<iostream>
using namespace std;

class construct
{
	public:     // Not private
	construct() 
	{
		cout<< "object is initialized automatically "<<endl;
	}
};
int main ()
{
	construct obj1,obj2;
	return 0;
}
Output :
object is initialized automatically
object is initialized automatically

// ----------  OR  ------------
#include<iostream>
using namespace std;

class construct
{
	public:
		int a,b,c;
	construct() 
	{
		a=10;
		b=30;
		c=a+b;
		cout<<"The output is = "<<c<<endl;
	}
};
int main ()
{
	construct obj1,obj2;
	return 0;
}
Output :
The output is = 40
The output is = 40

// ----------  OR  ------------
#include<iostream>
using namespace std;
class construct
{
	public:
		int a,b,c;
	construct() 
	{
		a=10;
		b=30;
		c=a+b;		
	}
	void output()
	{
		cout<<"The output is = "<<c<<endl;
	}
};
int main ()
{
	construct obj1,obj2;
	obj1.output();
	obj2.output();
	return 0;
}
Output :
The output is = 40
The output is = 40

// ----------  OR  ------------
#include<iostream>
using namespace std;

class construct
{
	public:
		int a,b,c;
	construct() 
	{
		a=10;
		b=30;
		c=a+b;
		output();		
	}
	void output()
	{
		cout<<"The output is = "<<c<<endl;
	}
};
int main ()
{
	construct obj1,obj2;	
	return 0;
}
Output :
The output is = 40
The output is = 40
Example : A simple C++ program to show constructor & destructor concept.
#include<iostream>
using namespace std;

class construct
{
	public:
		int a,b,c;
	construct() 
	{
		a=10;
		b=30;
		c=a+b;
		cout<<"The output is = "<<c<<endl;
		
	}	
	~ construct()
	{
		cout<<"Memory Deallocated"<<endl;
	}
};
int main ()
{
	construct obj1,obj2;	
	return 0;
}
Output :
The output is = 40
The output is = 40

Memory Deallocated
Memory Deallocated
Example : A C++ Program to show constructor overloading concept.
#include <iostream>
using namespace std;

class Student
{
	string sname;
	int roll;
	float tfee;
	
	public:
		Student()
		{
			sname = "default";
			cout << sname << endl;
		}		
		Student( string str )
		{
			sname = str;
			cout << sname << endl;
		}		
		Student( int roll1 , float tfee1 )
		{
			roll=roll1;
			tfee=tfee1;
			cout<<roll<<"  "<<tfee<<endl;
		}		
		Student( string str2 ,int roll2 , float tfee2 )
		{
			sname=str2;
			roll=roll2;
			tfee=tfee2;
			
			cout<<sname<<" "<<roll<<"  "<<tfee<<endl;
		}	
};

int main()
{
	Student stu;
	Student stu1( "codershelpline" );
	Student stu2(120,12.0123);
	Student stu3("Codershelpline",210,300.0123);		
	return 0;
}
Output :
default
codershelpline
120  12.0123
Codershelpline 210  300.012
Example : A C++ Program to show default constructor concept.
#include <iostream> 
using namespace std; 
  
class calculation 
{ 
public: 
    int x, y;   
    
    calculation()  //Deffult Constructor Called & Execute automatically when object is created.
    { 
        x = 22; 
        y = 310; 
    } 
}; 
  
int main() 
{ 
    calculation obj; 
    cout <<"First Default Value is : " << obj.x <<endl; 
    cout <<"Second Default Value is : " << obj.y;		  
    return 0;     
} 
Output :
First Default Value is : 22
Second Default Value is : 310

/* ------------------  OR  ----------------- */

#include <iostream> 
using namespace std;  
class calculation 
{ 
public: 
    int x, y;   
    
    calculation()  
    { 
        x = 22; 
        y = 310; 
    }
    void display()
    {		
        cout<< "The values are ="<<x<<" "<<y;	
    } 
}; 
  
int main() 
{ 
    calculation obj;
    obj.display();    		  
    return 0;     
} 
Output :
The values are =22 310

/* ------------------  OR  ----------------- */

#include <iostream>
using namespace std; 

class calculation
{
    
    private:
        int num1;
        int num2;    
    public:
        
        calculation(); 
        
        void input() 
        {
       	cout << endl<< "Enter First Value : "; 
	cin >> num1;
		
    	cout << "Enter Second Value : "; 
	cin >> num2;
	}	    
	   
        void output()
        {
        cout <<endl<<"First Value is : " << num1;
    	cout << endl <<"Second Value: " << num2 << endl;	
        }     
}; 

calculation:: calculation()
{
    num1 = 0;
    num2 = 0;
}
  
int main()
{
    calculation obj ;    
   
    cout <<"Value before user input : " ;
    obj.output();    
 
    obj.input();
    cout<<endl<<"Value after user Input : ";
    obj.output();      
     
    return 0;
}
Output :
Value before user input :
First Value is : 0
Second Value: 0

Enter First Value : 12
Enter Second Value : 10

Value after user Input :
First Value is : 12
Second Value: 10
Example : A C++ Program to show parameterised constructor concept.
#include <iostream> 
using namespace std; 
  
class calculation 
{ 
public: 
    int x, y;
    
    calculation(int x1, int y1)      //Parameterised Constructor .
    { 
        x = x1; 
        y = y1; 
    } 
    void display()
    {
    	cout<<x<<"  "<<y;
    }
}; 
  
int main() 
{ 
    calculation obj1(400,65);
    calculation obj2(12,35);
    calculation obj3(87,68);
    
   obj1.display();
   cout<<endl;
   
   obj2.display();
   cout<<endl;
   
   obj3.display();
		  
    return 0;     
} 
Output :
400  65
12  35
87  68

/* ------------------  OR  ----------------- */
#include <iostream> 
using namespace std; 
  
class calculation 
{ 
public: 
    int x, y;
    
    calculation(int x1, int y1);      //Define Constructor outside the class.
    
    void display()
    {
    	cout<<x<<"  "<<y;
    }
}; 

calculation :: calculation(int x1, int y1)     
    { 
        x = x1; 
        y = y1; 
    } 
  
int main() 
{ 
    calculation obj1(400,65);
    calculation obj2(12,35);
    calculation obj3(87,68);
    
   obj1.display();
   cout<<endl;
   
   obj2.display();
   cout<<endl;
   
   obj3.display();
		  
    return 0;     
} 
Output :
400  65
12  35
87  68

/* ------------------  OR  ----------------- */

#include <iostream> 
using namespace std; 
  
class calculation 
{ 
public: 
    int x, y;
    
    calculation(int x1, int y1)      //Parameterised Constructor .
    { 
        x = x1; 
        y = y1; 
    } 
};
  
int main() 
{ 
    calculation obj1(400,65);
    calculation obj2(12,35);
    calculation obj3(87,68);
    
    cout <<"First Parameterised Value is : " << obj1.x <<endl; 
    cout <<"Second Parameterised Value is : " << obj1.y<<endl;;
    
    cout <<endl<<"First Parameterised Value is : " << obj2.x <<endl; 
    cout <<"Second Parameterised Value is : " << obj2.y<<endl;;
    
    cout <<endl<<"First Parameterised Value is : " << obj3.x <<endl; 
    cout <<"Second Parameterised Value is : " << obj3.y;
		  
    return 0;    
} 
Output :
First Parameterised Value is : 400
Second Parameterised Value is : 65

First Parameterised Value is : 12
Second Parameterised Value is : 35

First Parameterised Value is : 87
Second Parameterised Value is : 68
Example : A Program in C++ to show copy constructor concept.
#include<iostream>
using namespace std;

class Example 
{   
   int a, b;
   public: 
   Example(int x, int y) 
   {
      a = x;
      b = y;      
      cout <<"\nParameterized Constructor values are = "<<a<<" "<<b;
   }   

   Example(Example &obj4) 
   {
      a = obj4.a;
      b = obj4.b;
      cout <<"\nCopy Constructor values are = "<<a<<" "<<b;
   }

   void display()
   {   	
   	cout <<"\nThe copied values are = "<<a<<" "<<b;
   }   
};

int main() {
   
   Example obj1(240, 500);
   
   Example obj2(obj1);
   
   Example obj3 = obj1;

   obj1.display();
   obj2.display();
   obj3.display();   
   
   return 0;
}
Output :
Parameterized Constructor values are = 240 500

Copy Constructor values are = 240 500
Copy Constructor values are = 240 500

The copied values are = 240 500
The copied values are = 240 500
The copied values are = 240 500

/* ------------------  OR  ----------------- */
//Factorial using copy constructor
#include<iostream>
using namespace std;

class Example 
{
    int val, fact;
    public:   

   Example(int temp) 
   {
      val = temp;
   }
   int factorial() 
   {
      fact = 1;
      for (int i = 1; i <= val; i++)
       {
         fact = fact * i;
       }
      return fact;
   }
};

int main() 
  {
   int n;
   cout << "\nEnter a value for factorial : ";
   cin>>n;
   
   Example obj1(n);
   
   Example obj2 = obj1;
   
   cout << "\n" <<"The factorial of "<< n << " is :" << obj1.factorial();
   cout << "\n" <<"The factorial of " << n << "after copy constructor is :" << obj2.factorial();
   
   return 0;
}
Output :
Enter a value for factorial : 5

The factorial of 5 is :120
The factorial of 5after copy constructor is :120
Example : A C++ Program to show destructor concept.
#include <iostream> 
using namespace std; 
  
class calculation 
{ 
public: 
    int x, y;
    
    calculation(int x1, int y1)      //Parameterised Constructor .
    { 
        x = x1; 
        y = y1; 
    } 
    
    ~calculation()     //Destructor creation
    {
    	cout<<endl<<"Destructor destroy object memory allocation";
    }
    
    void display()
    {
    	cout<<x<<"  "<<y;
    }
}; 
  
int main() 
{ 
    calculation obj1(400,65);
    calculation obj2(12,35);
    calculation obj3(87,68);
    
   obj1.display();
   cout<<endl;
   
   obj2.display();
   cout<<endl;
   
   obj3.display();
		  
    return 0;     
} 
Output :
400  65
12  35
87  68
Destructor destroy object memory allocation
Destructor destroy object memory allocation
Destructor destroy object memory allocation

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Categories: C++

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