The document discusses half and full subtractor circuits. It explains that a half subtractor performs subtraction of two bits, taking two inputs (minuend and subtrahend) and producing two outputs (difference and borrow out). The difference is 0 if the inputs are equal and 1 if they are not. Borrow out is 1 if the minuend is less than the subtrahend. A full subtractor performs subtraction of three bits, taking inputs of minuend, subtrahend, and borrow from the previous stage to produce difference and borrow out.

1. HALF SUBTRACTOR
III PHYSICS – 10.03.2022
Dr.R.Hepzi Pramila Devamani,
Assistant Professor of Physics,
V.V.Vanniaperumal College for Women,
Virudhunagar.

2. Half Subtractor
• The half subtractor is a combinational circuit which is used to
perform subtraction of two bits.
• It has two inputs X (minuend) and Y (subtrahend) and two
outputs D(difference) and Bout (borrow out).
• The symbol and truth table for half subtractor is shown in
figure.
• The difference output is 0 if X = Y and 1 if X ≠ Y.
• The borrow output Bout is 1 whenever X is less than Y, then
subtraction is done by borrowing 1 from the next higher order
bit.

3. Half Subtractor

4. Half Subtractor
• The Boolean expression for difference (D) and
borrow out (Bout) can be written as

5. Full Subtractor
• The full subtractor is a combinational circuit
which is used to perform subtraction involving
three bits.
• It has two inputs X (minuend) and Y (subtrahend)
and the borrow from the previous stage and two
outputs D(difference) and Bout (borrow out).
• The symbol and truth table for half subtractor is
shown in figure. The full subtractor can be
implemented using two subtractors and an OR
gate shown in figure.

6. Full Subtractor

7. Full Subtractor

8. Full Subtractor

9. THANK YOU