为什么我们在这个程序中需要虚拟（Turbo C++）？

我一直在使用 Turbo C++ 编写关于多重继承的代码，代码的目的是只获取输入并在控制台打印输入。我最初完成了以下代码，

// Program to demonstrate multiple inheritance

#include <conio.h>
#include <iomanip.h>
#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>>
#include <string.h>

class Company1
{
protected:
  int productID;
  char *productName;
  char *CompanyName;

public:
  void input_c1()
  {
    cout << "Provide Company 1 Details : " << endl;
    cout << setw(29) << setfill('-') << "" << endl;
    cout << "Enter the Product ID : ";
    cin >> productID;
    cout << "Enter the Product Name : ";
    gets(productName);
    cout << "Enter the Company Name : ";
    gets(CompanyName);
  }
};

class Company2
{
protected:
  int productID;
  char *productName;
  char *CompanyName;

public:
  void input_c2()
  {
    cout << endl << "Provide Company 2 Details : " << endl;
    cout << setw(29) << setfill('-') << "" << endl;
    cout << "Enter the Product ID : ";
    cin >> productID;
    cout << "Enter the Product Name : ";
    gets(productName);
    cout << "Enter the Company Name : ";
    gets(CompanyName);
  }
};

class SuperMarket : public Company2, public Company1
{
public:
  void Company_details()
  {
    cout << endl << "Company 1 details : " << endl;
    cout << setw(20) << setfill('-') << "" << endl;
    cout << "Product ID   : " << Company1::productID << endl;
    cout << "Product Name : ";
    print_string(Company1::productName);
    cout << endl;
    cout << "Company Name : ";
    print_string(Company1::CompanyName);
    cout << endl << endl;

    cout << "Company 2 details : " << endl;
    cout << setw(20) << setfill('-') << "" << endl;
    cout << "Product ID   : " << Company2::productID << endl;
    cout << "Product Name : ";
    print_string(Company2::productName);
    cout << endl;
    cout << "Company Name : ";
    print_string(Company2::CompanyName);
  }
  void print_string(char *ptr)
  {
    for (int i = 0; i != strlen(ptr); i++)
      cout << ptr[i];
  }
};

void main()
{
  char choice;
  clrscr();
  SuperMarket s;
  s.input_c1();
  s.input_c2();
  s.Company_details();
  cout << endl << "Do you want to exit ? (Y/N) : ";
  cin >> choice;
  if (choice == 'Y' || choice == 'y')
    exit(0);
  getch();
}

并在执行时得到如下输出，

But that wasn't the output which is expected because the Company Name of Company1 is dklm instead it was expected to be def. I further on tried to rectify it and made the derivation type of Company1 as virtual public and this resulted in correct output. I heard that virtual is used mostly in the cases of Diamond problem. Despite not being a Diamond problem it has resulted in the correct output. Can anyone please explain why did I get such kind of wrong output in the mentioned program and how did the virtual made to work the program properly in this case ?