Question

How many full adders are required to construct an m-bit parallel adder?

(a) m/2

(b) m

(c) m-1

(d) m+1

The question was posed to me in homework.

I want to ask this question from Quine McCluskey or Tabular Method of Minimization of Logic Functions topic in section Boolean Algebra and Minimization Techniques and Logic Gates of Digital Circuits

Answer 1

Right choice is (c) m-1

The best I can explain: We need adder for every bit. So we should need m bit adders. A full adder adds a carry bit to two inputs and produces an output and a carry. But the most significant bits can use a half adder which differs from the full adder as in that it has no carry input, so we need m-1 full adders and 1 half adder in m bit parallel adder.