7. The circuit shown in the Figure is a 4-bit circuit that can add or subtract numbers in a form used in computers

(positive numbers in true form; negative numbers in complement form).

a) Explain what happens when the Add /Subt. input is HIGH.

b) What happens when Add /Subt. is LOW?

Add/Subt, O

A₂ B₂

A B C

Ca

Σ

Σ₂

A₂ B₂

B C

Coat Σ

A, B₁

BC

M

144

A Bo

Ca

194

5