What is shallow copy?

What is shallow copy?

Default copy constructor of compiler copies all the member variables
from source to destination object. This is called shallow copy
constructor.

Example:

#include <iostream>
#include <string>
#include <conio.h>
using namespace std;
class Student
{

public:
     Student(int nAge)
     {
          m_nAge=nAge;
     }               
     int m_nAge;     
};
int main()
{
     Student obj(13);
     cout<<"Age1: "<< obj.m_nAge<<"\r\n";     
     Student obj1(obj);
     cout<<"Age2: "<<obj1.m_nAge<<"\r\n";
     getch();
     return 0;
}

Result:
Age1: 13
Age2: 13

Example 2:

#include <iostream>
#include <string>
#include <conio.h>
using namespace std;
  
class Student
{
public:
      Student(char* szName,int nAge)
      {
           m_szName =new char[20];
           strcpy(m_szName,szName);
           m_nAge=nAge;
      }
      ~Student()
      {
           delete[] m_szName;
           m_szName=NULL;
           cout<<"Memory destroyed \r\n";
      };
      int m_nAge;
      char *m_szName;
};
  
int main()
{
     Student *ptr=new Student("John",12);
     cout<<"Name: "<<ptr->m_szName<<"\r\n"<<"Age: "<< ptr->m_nAge<<"\r\n";
     {
          Student obj( *ptr);
          cout<<"Name: "<<obj.m_szName<<"\r\n"<<"Age: "<< obj.m_nAge<<"\r\n";

          //obj scope ends and ~Student() will be called
     }
     //Will Crash here
     //because m_szName is already freed in destructor.
     // this is the problem with shallow copy
     cout<<"Name: "<<ptr->m_szName<<"\r\n"<<"Age: "<< ptr->m_nAge<<"\r\n";
     delete ptr;
     getch();
     return 0;
}

Result:

Crash!!!!!!!!!!!