Shift Registers are storage devices that store binary data (1s, 0s). When a number fo Flip Flops are connected in series it becomes a shift register. These devices can be used to shift data serially--one bit of data at a time and built using RS, JK, or D style Flip Flops. There are two common circuit designs: * Asynchronous changes state each time the imput changes and only when triggered by a switch. * Synchronous changes state each time the imput changes and only when triggered by an edge clock signal pulse.