int main() 
{ 
    int *p ;

    p = (int *)0x0012ff80; 
    *p = 3; 

    printf("%d \n",*p);
    return 0; 
}

#include <iostream>

using namespace std; 

int main() 
{ 
/*    int *p ;
    
    p = (int *)0x0012ff80; 
    *p = 3; */

    int *p;
    long addr = 0x0012ff80;
    p = reinterpret_cast<int *>(&addr);
    *p = 3;
    cout << *p << endl;

    return 0; 
}