dynamic_cast

I have roughly gone thro' the defination. But still I am in confusion as to how
I can implement in C++. The example is as follows:

// dynamic_cast
#include <iostgream.h>
#include <exception> // the header file I do not know
class CBase{virtual void dummy() {} };
class CDerived: public CBase {int a;};
int main() {
try {
CBase *pba=new CBase;
CDerived *pd;
pd=dynamic_cast<CDerived* >(pba);
if (pd==0) cout << "Null pointer on first type-cast" << endl;
pd=dynamic_cast <CDerived* >(pbb);
if (pd==0 cout << "Null pointer on second type-cast" <<endl;
} catch (exception& e) {cout <<"Exception: " <<e.what();}
return 0;
}

 

Kindly give me some hint for the said example.

 

I wanted a brief about dynamic_cast. so pl. have ur valuable comments on it
BNRohit

 

Dynamic cast is a concept of Type conversions. It is used when we don’t know about type of object is. So at that time it performs type-safe downcasts where one of type is converting into some other types dynamically. It is used only with pointers objects and references to objects.
Example of Dynamic cast
if(JumpStm *j = dynamic_cast<JumpStm*>(&stm)) {
...
} else if(ExprStm *e = dynamic_cast<ExprStm*>(&stm)) {
...
}
Hop this will give you some guideline.