Why Gun *gun=&machinegun is working, but *gun=&machinegun not?

I learn polymorphism in c++ and that's my code.

   class Gun
     {

       public:
       virtual void Shoot()
       {
          cout<<"BANG";
       }
      }

    class Machinegun:public Gun
 {

      public:
         void Shoot() override
        {
           cout<<"DRRRRRRRRRRRRRRR";
        }
     }

    int main()
    {
    Gun *gun;
    Machinegun machinegun;

    //Why I can't use      *gun=&machinegun;??????

    //It works when I write  Gun *gun=&machinegun;

    }

It's not the same thing *gun=&machinegun<=>*gun=&machinegun; ??? I see no difference Thanks

It seems you are confusing with the two uses of * .

Gun * gun

Here the * is used for defining a pointer of type Gun. Because it comes after the type Gun .

If you are using * on an already defined object(pointer types specifically), like your second example it means to dereference that pointer, what comes back is the object that the pointer referenced to , and in your case Gun. A Gun object cannot be assigned with Machinegun* type

What you probably wanted is

Machinegun machinegun;
Gun * gun;
gun = &machinegun;