Four Men in a Car
Four men rode in a car: a mechanical engineer, an electrical engineer, a chemical engineer, and a computer engineer.
The car stalled out.
The mechanical engineer said, "It must be the pistons; let's repair them and be on our way."
The electrical engineer said, "It has to be the spark plugs; we'll replace them and be ready to roll in no time at all."
The chemical engineer said. "No, it's got to be bad gas; we'll flush the system and be on our way."
They turned to the computer engineer. "What do you think we should do?" they asked.
The computer engineer shrugged and said, "Let's get out of the car, close the doors, then get back in and try restarting it."