Control unit coordinates all processing activities in the CPU as well as input,storage and output operations. It determines which operation or instruction is to be executed next. To coordinate these activities,the control unit uses a system clock. The system clock sends electric signals as its means of communication, just like the way the traffic signals or a traffic officer does in a round about or junction to direct motorists and other road users. The number of pulses per second determines the speed of a microprocessor. The faster the clock pulses, the faster the CPU hence the faster the computer can process data.