What is shift register? Draw and explain left shift register and right shift register.

A shift register is a type of register that allows the bits to be shifted to the left or right. It is a sequential device with an array 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 specific feature i.e. they can perform simple load and store operations. The unique characteristic of shift register is that it can shunt its binary information in one or both directions.

There are two types of shift registers based on the shifting pattern:

1. Left Shift Register
2. Right Shift Register

Left Shift Register

In the left shift register, the binary data is shifted from the least significant bit (LSB) to the most significant bit (MSB).

Here is a simple diagram of a 4-bit left shift register:

  LSB                                 MSB
  Q0  -->  Q1  -->  Q2  -->  Q3

In this diagram, Q0, Q1, Q2, and Q3 represent the 4-bits in the register. The arrow indicates the direction of the shift. When a left shift operation is performed, the bits are moved one place to the left.

For example, if we have the binary number 1011 in the register and perform a left shift, the result would be 0110.

Right Shift Register

In the right shift register, the binary data is shifted from the most significant bit (MSB) to the least significant bit (LSB).

Here is a simple diagram of a 4-bit right shift register:

  MSB                                 LSB
  Q3  -->  Q2  -->  Q1  -->  Q0

In this diagram, Q3, Q2, Q1, and Q0 represent the 4-bits in the register. The arrow indicates the direction of the shift. When a right shift operation is performed, the bits are moved one place to the right.

For example, if we have the binary number 1011 in the register and perform a right shift, the result would be 1101.

Shift Register Type	Shift Direction	Example
Left Shift Register	LSB to MSB	1011 becomes 0110
Right Shift Register	MSB to LSB	1011 becomes 1101

In both types of shift registers, the vacant bit position after the shift operation is usually filled with a zero. However, in some cases, it can be filled with the last bit of the number before the shift, or with a bit provided by a user or a program.