Computing and control are deeply intertwined. As a theory and practice of engineering, control was a main impetus for the emergence of modern computing in the 1940s. With its broad connotations of mastery and steering, control seems intuitively applicable to many of computers' uses. With versatility, however, comes ambiguity. The concept has been applied to a range of disparate phenomena, at different levels of abstraction. This article gives seven definitions of control and shows that the theme and the diversity of control is relevant to the social history of computing. However, historians of computing should be careful to distinguish between literal and metaphorical use and between different aspects of control.