If your microwave oven is a computer, define its operating system and user interface.

If the microwave is considered as the computer system instead then the operating system in the microwave that deals with the whole functioning and carrying out operation will be done with the help of the embedded operating system.

The user interface in the microwave system which will help the user to interact with the device system will be done with the help of the keys that are present in the microwave for entering the input as options like start,stop,pause etc,mode and time.

answer; its the top layer;

i'm pretty sure data is stored in a form