Control+Bus

The control bus is the physical connections that carry control information between the CPU and other devices within the computer. Whereas the data bus carries actual data that is being processed, the control bus carries signals that report the status of various devices. For example, one line of the bus is used to indicate whether the CPU is currently reading from or writing to main memory.  The control bus is used by the CPU to direct and monitor the actions of the other functional areas of the computer.