C++ code with a coffee menu. I have to write out the customer order out to a file which I got but when I tried to write out a function it won't work. The function is to calculate the cost of the order and it works when I just display it on screen, but when I tried to write it out I get an error.

fstream order("coffee.dat", ios::out|ios::app); order.write(reinterpret_cast(&c),sizeof(c)); order<<" OrderNumber:"<< e.order<<" CoffeeName:"<' and 'void')"