how to declare a pointer c++ code example

Example 1: what is this pointer in c++

Every object in C++ has access to its own address through an important pointer called this pointer.
 The this pointer is an implicit parameter to all member functions. 
Therefore, inside a member function,
 this may be used to refer to the invoking object.

Friend functions do not have a this pointer,
 because friends are not members of a class. 
Only member functions have a this pointer.

Example 2: c++ pointers

// my first pointer
#include <iostream>
using namespace std;

int main ()
{
  int firstvalue, secondvalue;
  int * mypointer; //creates pointer variable of type int

  mypointer = &firstvalue;
  *mypointer = 10;
  mypointer = &secondvalue;
  *mypointer = 20;
  cout << "firstvalue is " << firstvalue << '\n';   //firstvalue is 10
  cout << "secondvalue is " << secondvalue << '\n'; //secondvalue is 20
  return 0;
}

Example 3: Function pointer C++

void one() { cout << "One\n"; }
void two() { cout << "Two\n"; }


int main()
{
	void (*fptr)(); //Declare a function pointer to voids with no params

	fptr = &one; //fptr -> one
	*fptr(); //=> one()

	fptr = &two; //fptr -> two
	*fptr(); //=> two()

	return 0;
}