3) Program gives working of Constructors and Destructors.

 source file name: destructor.cpp
#include<iostream.h>
#include<conio.h>
#include<math.h>

 int cnt;
 class beta
 {
 public:
 beta()
 {
 cnt++;
 cout<<"\n Object created No.: "<< cnt;
 }
 ~beta()
 {
  cout<<"\n Object destroyed No.: "<< cnt;
  cnt--;
 }

 } ;
void main()
  {
  clrscr();
  cout<<" Constructor and Destructor program"<<endl;
  cout<<"\n Main fuction block";
  beta b1,b2,b3,b4;
  {
  cout<<"\n now we are in block: 1"<<endl;
  beta b5;
  }
  {
  cout<<"\n now we are in block: 2"<<endl;
  beta b6;
  }
    cout<<"\n re enter Main fuction block";
  getch();
   }
 

output: