Shift registers

Shift registers are a type of sequential logic circuit, mainly for storage of digital data.  They are a group of flip-flops connected in a chain so that the output from one flip-flop becomes the input of the next flip-flop.  Most of the registers possess no characteristic internal sequence of states.  All the flip-flops are driven by a common clock, and all are set or reset simultaneously.

There are varios types of Registers:-

Serial In - Serial Out
Serial In - Parallel Out
Parallel In - Serial Out
Parallel In - Parallel Out
Shift Register Counters
                          (i) Ring Counters
                          (ii) Johnson Counters