C / C++ / MFC

#include <iostream.h> 
 
struct structA 
{ 
  int iMember; 
  char *cMember; 
}; 
 
int main(int argc, char* argv[]) 
 
{ 
  structA instant1,instant2; 
 
  char c = 'a';     
 
  instant1.iMember = 1; 
  instant1.cMember = &c;  
  instant2 = instant1; 
 
  cout << *(instant1.cMember) << endl; 
  *(instant2.cMember) = 'b'; 
  cout << *(instant1.cMember) << endl; //I want to know why change instant2 and the instant1 change!
 
  getchar(); 
} 

#include <iostream>
using namespace std;
#pragma pack(8)

struct example1
{
       short a;
       long b;
};

struct example2
{
       char c;
       example1 struct1;
       short e;
};

#pragma pack()

int main()
{
       example2 struct2;
       cout << sizeof(example1) << endl;    //8
       cout << sizeof(example2) << endl;    //16
       cout << (unsigned int)(&struct2.struct1) - (unsigned int)(&struct2)
            << endl;                              //4
            
       getchar();
}

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