Q.What is a register?

A register is a group of flip-flops connected together to store more than one bit of data — an n-bit register uses n flip-flops. A shift register adds the ability to move (shift) the stored bits one position along the chain on each clock pulse, which makes it useful for temporary storage, serial-to-parallel and parallel-to-serial conversion, and data transfer between digital systems.

Shift registers are classified by how data is loaded in and read out, giving four standard types. In a SISO (Serial-In Serial-Out) register, data enters one bit at a time and leaves one bit at a time, so bits ripple through the chain. In a SIPO (Serial-In Parallel-Out) register, data is fed in serially but all stored bits are read out together on separate lines. In a PISO (Parallel-In Serial-Out) register, all bits are loaded at once through parallel lines and then shifted out one at a time; the same line is used to transfer data in and out. In a **PIPO (Parallel-In …