how to do pointers in c++ code example

Example 1: pionter in c++

#include <iostream>
using namespace std;
int main(){
   //Pointer declaration
   int *p, var=101;
 
   //Assignment
   p = &var;

   cout<<"Address of var: "<<&var<<endl;
   cout<<"Address of var: "<<p<<endl;
   cout<<"Address of p: "<<&p<<endl;
   cout<<"Value of var: "<<*p;
   return 0;
}

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;
}