ALU 101 Adder Circuits and Addition Logic

Question 1

What are the two outputs produced by a half adder?

Accepted Answer

Sum and Carry

Answer

A half adder produces a Sum output (XOR of the two input bits) and a Carry output (AND of the two input bits).

Question 2

How many inputs does a full adder have?

Accepted Answer

3

Answer

A full adder has three inputs: two operand bits (A and B) and a carry-in (Cin) from a previous stage.

Question 3

Which logic gate implements the Sum output of a half adder?

Accepted Answer

XOR gate

Answer

The Sum output of a half adder is implemented with an XOR gate because it outputs 1 only when the two input bits differ.

Question 4

What is the correct Boolean expression for the carry-out of a full adder?

Accepted Answer

(A AND B) OR (Cin AND (A XOR B))

Answer

The carry-out expression (A·B) + (Cin·(A⊕B)) covers carry generation when both A and B are 1, and carry propagation when Cin passes through.

Question 5

In a ripple carry adder, how does the carry signal travel through the circuit?

Accepted Answer

The carry output of each stage feeds into the carry input of the next stage

Answer

In a ripple carry adder, the carry-out of each full adder is connected to the carry-in of the next higher-order full adder, causing carries to ripple sequentially.

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test

ALU 101 Adder Circuits and Addition Logic