Buffer register is a simplest type of register constructed using four D flip flop.
This is a 4 bit register, but we can construct an n-bit register by following the same principle.
The register is also called as the buffer register
Each D flip flop is negative edge triggered and all the flip flop are connected to a common clock signal. Hence all of them are triggered at the same time, that is all the flip-flop will change their state at the same instant of time.
Buffer register are used for temporary storage of digital words. 