A half adder has

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  1. 2 inputs and 2 outputs
  2. 2 inputs and 3 outputs
  3. 3 inputs and 3 outputs
  4. 1 input and 1 output

Answer (Detailed Solution Below)

Option 1 : 2 inputs and 2 outputs
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Half adder circuit:

half adder circuit has 2 inputs and 2 outputs.

A half adder circuit is basically made up of an AND gate and an XOR gate as shown below:

Sum (S) = A⊕B

Carry = A.B

The truth table is as shown:

INPUTS

OUTPUTS

A

B

Sum

CARRY

0

0

0

0

0

1

1

0

1

0

1

0

1

1

0

1

 

A full adder circuit has three binary digit inputs (two input bits and one carry input bit) and two binary digit outputs, Sum bit and carry output bit.

A Full adder can be realized using two half adders as shown:

The truth table of a full adder logic is:

A

B

C

Cin

S

0

0

0

0

0

0

0

1

0

1

0

1

0

0

1

0

1

1

1

0

1

0

0

0

1

1

0

1

1

0

1

1

0

1

0

1

1

1

1

1

The Sum output bit of a full adder is given by:

S = A ⊕ B ⊕ C

The carry output bit of a full adder is given by:

X1 = AB + BC + AC

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