The concept of a coordinator is proposed for control of modular discrete-event systems. The coordinator makes all subsystems conditionally independent generators as defined in the paper. The coordinator receives part of the partial observations of the subsystems and its task is to satisfy the global part of the specification and of the nonblockingness. The complete supervisor then consists of the coordinator, its supervisor, and the local supervisors for the subsystems. An example of control of a distributed discrete-event system shows that a coordinator is necessary for achieving safety and nonblockingness.