# 4-Bit Parallel Adder/Subtractor – 1 MCQ’s

This set of Digital Circuits Multiple Choice Questions & Answers (MCQs) focuses on “4-Bit Parallel Adder/Subtractor – 1″.

1. Why XOR gate is called an inverter?
a) Because of the same input
b) Because of the same output
c) It behaves like a NOT gate
d) It behaves like a AND gate

2. Controlled buffers can be useful ____________
a) To control the circuit’s output into the bus
b) In comparison of component’s output with its input
c) In increasing the output from its low input
d) All of the Mentioned

3. Controlled inverter is also known as ____________
a) Controlled buffer
b) NOT gate
c) Both controlled buffer and NOT gate
d) Controlled gate

4. A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is ____________
a) Ex-NOR gate
b) OR gate
c) Ex-OR gate
d) NAND gate

5. What is the major difference between half-adders and full-adders?
b) Full adders can handle double-digit numbers
c) Full adders have a carry input capability
d) Half adders can handle only single-digit numbers

6. How many basic binary subtraction operations are possible?
a) 1
b) 4
c) 3
d) 2

7. What is the first thing you will need if you are going to use a macro-function?
a) A complicated design project
b) An experienced design engineer
c) Good documentation
d) Experience in HDL

8. The binary subtraction of 0 – 0 =?
a) Difference = 0, borrow = 0
b) Difference = 1, borrow = 0
c) Difference = 1, borrow = 1
d) Difference = 0, borrow = 1

9. When performing subtraction by addition in the 2’s-complement system ____________
a) The minuend and the subtrahend are both changed to the 2’s-complement
b) The minuend is changed to 2’s-complement and the subtrahend is left in its original form
c) The minuend is left in its original form and the subtrahend is changed to its 2’s-complement
d) The minuend and subtrahend are both left in their original form

10. What are the two types of basic adder circuits?
a) Sum and carry
c) Asynchronous and synchronous
d) One and two’s-complement

11. Which of the following is correct for full adders?
a) Full adders have the capability of directly adding decimal numbers
b) Full adders are used to make half adders
c) Full adders are limited to two inputs since there are only two binary digits
d) In a parallel full adder, the first stage may be a half adder

12. The selector inputs to an arithmetic/logic unit (ALU) determine the ____________
a) Selection of the IC
b) Arithmetic or logic function
c) Data word selection
d) Clock frequency to be used