A shift register is a digital memory circuit found in calculators, computers, and data-processing systems. Bits (binary digits) enter the shift register at one end and emerge from the other end. The two ends are called left and right. Flip flops, also known as bistable gates, store and process the data.
In its most basic form, the shift register is a bidirectional FIFO (first-in first-out) circuit. When a bit is input on the left, all the bits in the register move one place to the right, and the rightmost bit disappears. When a bit is input on the right, all the bits move one place to the left, and the leftmost bit disappears.