The arithmetic logic unit (ALU), which performs arithmetic and logical operations.
The control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
The OS shell allows access to the operating system services
Because most people really don't want or need to see what's in there.
If you want to, open the door during the cycle. It won't harm anything.
If you're curious to see a dishwasher in action, some appliance showrooms have a display model, where the spray parts and the racks are in an entirely transparent box. They're to show how powerfully and completely the stuff inside will get cleaned, but you can also see how the dishwasher is intended to work, by filling with just a couple of inches of water, and then recirculating it for the duration of the cycle, to loosen the stuff on the dishes.
Answer:
(GUI) stands for Graphical User Interface
