"A system is any portion of the universe set aside for certain specified purposes. For our concern, a system is set aside from the universe in a manner that will enable this system to be built without having to consider the total universe. Therefore, the system is set aside from the universe by its inputs and outputs--its boundaries. The system may be said to be in operation when its inputs are being transformed into the required outputs. (Incidently, we are not here concerned with completely closed systems.) The systems that do concern us all have a number of components within their boundaries which together effect the transformation of the inputs to the required outputs. A man-machine system is one in which the components are comprised of both men and machines. Keep in mind that it is only when the components are operating together that the inputs are transformed into the proper outputs. Within this definition, a system may be anything from an amoeba to a transistor, to a weapon system, to a planet--depending on what the specified inputs and outputs are. The systems that specifically concern us are complex man-machine systems that have to be built."