Question

The number of full and half adders are required to add 16-bit number is __________

(a) 8 half adders, 8 full adders

(b) 1 half adders, 15 full adders

(c) 16 half adders, 0 full adders

(d) 4 half adders, 12 full adders

The question was asked in an interview.

Query is from Quine McCluskey or Tabular Method of Minimization of Logic Functions in section Boolean Algebra and Minimization Techniques and Logic Gates of Digital Circuits

Answer 1

The correct choice is (b) 1 half adders, 15 full adders

To explain I would say: Half adder has two inputs and two outputs whereas Full Adder has 3 inputs and 2 outputs. One half adder can add the least significant bit of the two numbers whereas full adders are required to add the remaining 15 bits as they all involve adding carries.