Is this design pattern correct (builder)

Hello NG,

i am just learning various Design Patterns and now i am not sure, if
this design is correct (Builder) or if i should use an other pattern.

I have various classes (here ChildA and ChildB) derived from class Base.
Now i want to create an object, but i don't want to know which class to
instantiate.

All classes have "pseudo"-methods/codes to keep it very simple.

------------------ cut here ------------------
class Base
{
  public:
    virtual ~Base() {}; // hack!
    virtual start() = 0;
    virtual stop() = 0;

    // with empty methods only for default implementation
    void create (const char* last, const char* first) {} ;
    void create (const char* last) {} ;
};

// --------------------------------------------

class ChildA : public Base
{
  public:
    ChildA();
    void start();
    void stop();

    // ok, child_a implements this create method
    void create(const char* name)
    { /* do something */}
};

// --------------------------------------------
class ChildB : public Base
{
  public:
    ChildB();
    void start();
    void stop();

    // ok, child_a implements the other create method
    void create (const char* name1, const char* name2)
    { /* do something else */ }
};

// --------------------------------------------
class Builder
{
  public:
    Base* createObject(int type)
    {
      if (type = 1)
        return new ChildA;
      if (type = 2)
        return new ChildB;

      // exception handling
      ...
      ...
    }
} ;

// --------------------------------------------

int main()
{
  Base base = Builder::createObject(2); // ChildB
  base->create("Doe", "Johnny");
  base->start();
 
  /* do the rest */
  ...
  ...
}

------------------ cut here ------------------

Thanks a lot for your answers
Mike