Registers are high-speed memory units that are part of a computer's processor. They can hold data like bit sequences or single pieces of information. Registers are made up of flip flops, with multiple flip flops combined to create registers of different bit sizes (e.g. 4 flip flops for a 4-bit register). Registers can be constructed to operate in different input/output configurations, including serial input serial output (SISO), serial input parallel output (SIPO), parallel input serial output (PISO), and parallel input parallel output (PIPO).

1. Registers
• Computer registers are memory storing units that operate
at high speed. It's a component of a computer's processor.
It can hold any type of data, including a bit sequence or a
single piece of data. Eight registers, a memory unit, and a
control unit make up a basic computer. These devices must
be connected on a regular basis.
• Registers are a type of computer memory used to accept,
store, and transfer data and instructions used by the CPU
right away. Processor registers refer to the registers used by
the CPU. During the execution of a program, registers are
used to store data temporarily. In most cases, the number
of bits that a register can hold is used to determine its size.

2. How is Register made
• Register is made with help of flip flop.
• Since flip flop has capacity to store one bit of
data using this concept we merge multiple flip
to form a Register
• If the Register is of 4 bits than the total
number of flip will be 4 (4 Flip Flop=1(4 bit
Register)
• Similarly for 8 bit Register(8 Flip Flops=1(8 bit
Register) and so on.

3. We can make Registers in the following
ways
• SISO(Serial Input Serial Output)
• SIPO(Serial Input Parallel Output)
• PISO(Parallel Input Serial Output)
• PIPO(Parallel Input Parallel Output)

4. SISO
• We can make it with the help of D Flip Flop for making Register. It will take Input Serial wise and produce output
Serial wise also.
• 4 bit Register(4 Flip Flop)
Clk 1:- 1 X X X
Clk 2:- 0 1 X X
Clk 3:- 0 0 1 X
Clk 4:- 1 0 0 1 (1
Clk 5:- X 1 0 0 (01
Clk 6:- X X 1 0 (001
Clk 7:- X X X 1 (1001)
D3 D1 Q1 Q0
D0
Q3 D2 Q2
Din 1001
clk
1001

5. SIPO
• We can make it with the help of D Flip Flop for making Register. It will take Input Serial wise and produce parallel
wise output.
• 4 bit Register(4 Flip Flop)
Clk 1:- 1 0 0 0
Clk 2:- 0 1 0 0
Clk 3:- 0 0 1 0
Clk 4:- 1 0 0 1 (1001)
D3 D1 Q1 Q0
D0
Q3 D2 Q2
Din 1001
clk
1 0 0 1

6. PISO
• We can make it with the help of D Flip Flop for making Register. It will take parallel wise and produce serial wise
output also.
• 4 bit Register(4 Flip Flop)
Clk 1(parallel inout):- 1 0 0 1
Clk 2:- X 1 0 0(1
Clk 3:- X X 1 0(10
Clk 4:- X X X 1 (1001)
D3 D1 Q1 Q0
D0
Q3 D2 Q2
Din 1001
clk
1001

7. PIPO
• We can make it with the help of D Flip Flop for making Register. It will take parallel wise and produce parallel
wise output also.
• 4 bit Register(4 Flip Flop)
Clk 1(parallel input):- 1 0 0 1
D3 D1 Q1 Q0
D0
Q3 D2 Q2
Din 1001
clk
1001
1 0 0 1