This paper accompanies a tutorial aimed at introducing the basics of system and control theory so as to foster their utilisation for the management, but most important for the design, of computing systems. The tutorial is divided into three parts. The first one introduces the fundamental concepts of dynamic system and feedback and gives an overview of the properties that a control system has to enjoy, together with the main techniques to prescribe and assess these properties formally. The second part discusses a few computer-related application examples, revisiting the addressed problems from scratch with a system-centric viewpoint, and comparing the solutions - and most important, the way the system is viewed and designed - with state-of-the-art alternatives. This leads to envisage the potentialities of control-based computing systems design, but at the same time to identify open problems, both technological and methodological: an overview of these aspects is the subject of the third part. This companion paper motivates the tutorial, illustrates its rationale, and provides a commented outline.