CIE A2 CS Chapter 19 - Logic Circuits

The purpose of a half adder in logic circuits is to:

• Add two single binary digits and provide the sum and carry output.

• Subtract two binary numbers and provide the difference.

• Multiply two binary numbers and provide the product.

• Divide two binary numbers and provide the quotient.

What does a half adder perform?

• Binary subtraction of two bits

• Binary addition of two bits

• Decimal addition of two numbers

• Decimal subtraction of two numbers

A half adder takes two inputs (A and B) and produces two outputs: Sum (S) and ______.

• Carry (C)

• Difference (D)

• Product (P)

• Quotient (Q)

What is the truth table for a half adder?

• A) 0 0 | 0 0; 0 1 | 0 1; 1 0 | 0 1; 1 1 | 1 0

• B) 0 0 | 0 0; 0 1 | 1 0; 1 0 | 1 0; 1 1 | 0 1

• C) 0 0 | 0 0; 0 1 | 1 1; 1 0 | 1 1; 1 1 | 0 0

• D) 0 0 | 0 1; 0 1 | 1 0; 1 0 | 1 0; 1 1 | 1 1

What is the result of the binary addition 0 + 0?

• A) 0 0

• B) 1 0

• C) 0 1

• D) 1 1

Fill in the blank: The Sum (S) is the ___ of the inputs, and the Carry (C) is the ___ of the inputs.

• XOR, AND

• AND, OR

• OR, XOR

• NAND, NOR

The difference between a half adder and a full adder is:

• A half adder has two inputs and a full adder has three inputs.

• A half adder can add three bits and a full adder can add two bits.

• A half adder is used for subtraction and a full adder is used for addition.

• A half adder is more complex than a full adder.

What is the main difference between a half adder and a full adder?

• A half adder has two inputs and no carry input, while a full adder has three inputs, including a carry input.

• A half adder has three inputs, while a full adder has two inputs and no carry input.

• Both have the same number of inputs.

Fill in the blank: A full adder allows chaining of adders to perform multi-bit addition, as it includes a _________.

• carry-in bit.

• sum output.

• overflow bit.

• parity bit.

The logic gates used in a half adder are:

• AND and OR

• OR and NOT

• XOR and AND

• NAND and NOR