Q. What do you mean by Registers?

A register is a collection of flip flops (and some basic combinational gates to perform different binary arithmetic and logic operations), where each flip-flop is used to store 1 bit of information. Figure (a) shows the block diagramof a 4-bit shift-right register that uses D flip-flops. JKFFs and SRFFs are also used in shift-register construction. Observe in the timing diagram of Figure (b) that each successive clock pulse transfers (or shifts) the data bit from one flip-flop to the next one on the right. The waveforms also reveal that the data are read into the register serially and appear at the output in serial form. The shift register is then known as a serial-in serial-out (SISO) register.

PISO (parallel-in serial-out), SIPO (serial-in parallel-out), and PIPO (parallel-in parallel- out) registers are also often used to read in the input data and read out the output data in a convenient way that is needed for the operations involved. Right-shifting registers are employed in multiplication algorithms, whereas left-shifting registers are utilized in division algorithms.

Registers that are capable of shifting the data to the left or right are known as bidirectional shift registers. The register along with additional gates on a single chip forms an IC component known as the universal register, which usually includes the shift-left, shift-right, parallel-input, and no-change operations.