Example

Attendance system in a school.

	The teacher takes register to see who is not in today (INPUT).
	The data is loaded into the school database and PROCESSED to create an attendance record of each pupil.
	An OUTPUT is printed for a student who has been absent.
	This FEEDBACK means the teacher needs to find out why the pupil has been absent and the reason recorded in the INPUT once more.
	The FEEDBACK will also hopefully cause the pupil to have a better attendance record.

There are two kinds of feedback: Negative and Positive.

With negative feedback if the input goes up then the output goes down. So when some of the output added to the input, it effectively dampens down the chance of the system becoming unstable. Negative feedback is used to keep a system stable.

Positive feedback: If the input goes up, then the output also goes up. Positive feedback is not commonly used as it tends to make the system unstable.