[d flipflop output]

No, you need to have loop with the function registered as SC_THREAD. For your code, it will be:

  

  void d_operation()
    { while(1){
      
        if (reset.read()==1)
        {
        
        d_out = 0;
    //    std::cout << "reset= " << reset << "...din=  " << d_in << ".....d_out" << d_out << std::endl;
           }
        else
        {
            //d_out.write(d_in.read());
          d_out=d_in;
        //    wait(1, SC_NS);
        //    std::cout << "reset= " << reset << "...din=  " << d_in << ".....d_out" << d_out << std::endl;
            }
      wait();
    }
    }

 

[d flipflop output]

You have registered d_operation() as a thread. Ideally a thread should have an infinite loop and a wait(). Adding that, you can see changes to your d_out.

Also, how about having another thread that does the reset job?