On the fly is a phrase used to describe something that is being changed while the process that the change affects is ongoing. It is used in the automotive, computer, and culinary industries. In cars, on the fly can be used to describe the changing of the cars configuration while it is still driving. Processes that can occur while the car is still driving include switching between two wheel drive and four wheel drive on some cars and opening and closing the roof on some convertible cars. In computing, on the fly CD writers can read from one CD and write the data to another without saving it on a computer's memory. Switching programs or applications on the fly in multi-tasking operating systems means the ability to switch between native and/or emulated programs or applications that are still running and running in parallel while performing their tasks or processes, but without pausing, freezing, or delaying any, or other unwanted events. Switching computer parts on the fly means computer parts are replaced while the computer is still running. It can also be used in programming to describe changing a program while it is still running. In restaurants and other places involved in the preparation of food, the term is used to indicate that an order needs to be made right away.