const int* pn과 int* const pn의 차이는?

/*17.cpp*/
#include 
using std::cout;
using std::endl;
int main()
{
    int pNum = 3;
    int qNum = 4;
   
    const int* pn = &pNum;
    int* const pn2 = &qNum;;
 
    //const int*
    //메모리 주소 변경
    pn = &pNum;
    cout << pn << endl;   
    pn = &qNum;
    cout << pn << endl;    
   
    //포인팅 된 값을 변경하지 못함
    *pn = pNum;
    cout << *pn << endl;   
    *pn = qNum;
    cout << *pn << endl;   
   
       
    //int* const
    //메모리 주소 변경하지 못함
    pn2 = &pNum;
    cout << pn2 << " " << *pn2 << endl;   
    pn2 = &qNum;
    cout << pn2 << " " << *pn2 << endl;    
    
    //포인팅 된 값을 변경
    *pn2 = pNum;
    cout << pn2 << " " << *pn2 << endl;   
    *pn2 = qNum;
    cout << pn2 << " " << *pn2 << endl;    
            
    return 0;
}

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