C++ Class constructor pro

A simple program demonstrating C++ class

#include 

#include

using namespace std;

class cl 

{

  int i; 

public:

  int get_i();

  void put_i(int j);

};

int cl::get_i()

{

  return i;

}

void cl::put_i(int j)

{

  i = j;

}

int main()

{

  cl s;

  s.put_i(10);

  cout << s.get_i() <

  return 0;

}

Constructor

#include 

#include

using namespace std;

class Box

{

  public:

    double length;

    double breadth;

    double height;

    Box(double lengthValue, double breadthValue, double heightValue)

    {

      cout << "Box constructor called" << endl;

      length = lengthValue;

      breadth = breadthValue;

      height = heightValue;

    }

    double volume()

    {

      return length * breadth * height;

    }

};

Using inline initialization in constructor

#include 

#include

using namespace std;

class Box

{

  public:

    double length;

    double breadth;

    double height;

    Box(double lv = 1.0, double bv = 1.0, double hv = 1.0):length(lv),

              breadth(bv),height(hv)

    {

      cout << "Box constructor called" << endl;

    }

       double volume()

    {

      return length * breadth * height;

    }

};

int main()

{

  Box firstBox(80.0, 50.0, 40.0);

  double firstBoxVolume = firstBox.volume();

  cout << endl;

  cout << "Size of first Box object is "

       << firstBox.length  << " by "

       << firstBox.breadth << " by "

   << firstBox.height

       << endl;

  cout << "Volume of first Box object is " << firstBoxVolume

       << endl;

  return 0;

}

Copy constructor 

#include 

#include 

using namespace std;

class myclass 

{

  int *p;

public:

  myclass(int i);

  ~myclass();

  int getval() { return *p; }

};

myclass::myclass(int i)

{

  cout << "Allocating p\n";

  p = new int;

  if(!p) 

 {

    cout << "Allocation failure.\n";

    exit(1); 

  }

  *p = i;

}

myclass::~myclass()

{

  cout << "Freeing p\n";

  delete p;

}

void display(myclass ob)

{

  cout << ob.getval() << '\n';

}

int main()

{

  myclass a(10);

  display(a);

  return 0;

}

Destructor 

#include 

#include

#include 

using namespace std;

class myclass 

{

  int *p;

public:

  myclass(int i);

  ~myclass();

  int getval() { return *p; }

};

myclass::myclass(int i)

{

  cout << "Allocating p\n";

  p = new int;

  if(!p) 

 {

    cout << "Allocation failure.\n";

    exit(1); 

  }

  *p = i;

}

myclass::~myclass()

{

  cout << "Freeing p\n";

  delete p;

}

void display(myclass &ob)

{

  cout << ob.getval() << '\n';

}

int main()

{

  myclass a(10);

  display(a);

  return 0;

}