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

A shift register is a type of sequential logic circuit, mainly used for storage of digital data. It is a group of flip flops, where each flip flop is driven by the output of the previous one. The data bits on the inputs are shifted to the outputs on each clock cycle. Shift registers can have both parallel and serial inputs and outputs.

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

1. Left-Shift Register
2. Right-Shift Register

Left-Shift Register

In a left-shift register, the binary information is shifted from a lower order flip flop to a higher order flip flop. Here, the data bit is transferred from one flip flop to the next left flip flop at each clock pulse.

Let's consider a 4-bit left-shift register:

D3 ----> Q3 ----> D2 ----> Q2 ----> D1 ----> Q1 ----> D0 ----> Q0

In this case, the data at D3 is shifted to Q3, D2 to Q2, D1 to Q1, and D0 to Q0 at each clock pulse.

Right-Shift Register

In a right-shift register, the binary information is shifted from a higher order flip flop to a lower order flip flop. Here, the data bit is transferred from one flip flop to the next right flip flop at each clock pulse.

Let's consider a 4-bit right-shift register:

D0 ----> Q0 ----> D1 ----> Q1 ----> D2 ----> Q2 ----> D3 ----> Q3

In this case, the data at D0 is shifted to Q0, D1 to Q1, D2 to Q2, and D3 to Q3 at each clock pulse.

Here is a table that summarizes the main differences between left-shift and right-shift registers:

Left-Shift Register	Right-Shift Register
Shifts data from lower order flip flop to higher order flip flop	Shifts data from higher order flip flop to lower order flip flop
Data is transferred from one flip flop to the next left flip flop at each clock pulse	Data is transferred from one flip flop to the next right flip flop at each clock pulse
Example: D3 to Q3, D2 to Q2, D1 to Q1, D0 to Q0	Example: D0 to Q0, D1 to Q1, D2 to Q2, D3 to Q3

In conclusion, shift registers are an important part of digital systems and are used in a variety of applications, including data storage, data transfer, and data manipulation. The direction of shift (left or right) depends on the specific requirements of the system.