105. OCR A Level (H446) SLR15 – 1.4 Half & full adders

What is the result of adding the binary equivalents of 43 and 107 together?

• 10101010

• 10010110

• 10010101

• 11011010

Answer explanation

Adding the binary equivalents of 43 (101011) and 107 (1101011) gives 10010110, which is the correct answer choice.

What logic gate represents the 'digit' output in a half adder?

• AND gate

• OR gate

• XOR gate

• NAND gate

Answer explanation

The XOR gate represents the 'digit' output in a half adder as it performs the exclusive OR operation, which outputs true only when the inputs differ.

What logic gate represents the 'C out' output in a half adder?

• NAND gate

• OR gate

• AND gate

• XOR gate

Answer explanation

The 'C out' output in a half adder is represented by an AND gate as it performs the logical AND operation on the input bits to generate the carry output.

How many inputs does a full adder have?

• Two

• Five

• Three

• Four

Answer explanation

A full adder has three inputs: A, B, and a carry-in (Cin), making the correct answer choice 'Three'.

What additional component does a full adder circuit include compared to a half adder?

• A NOR gate

• A NAND gate

• A NOT gate

• An OR gate

Answer explanation

A full adder circuit includes an OR gate in addition to the components of a half adder.

What is the primary function of a half adder?

• To divide two binary numbers

• To subtract two binary numbers

• To add two binary numbers without carrying

• To multiply two binary numbers

Answer explanation

The primary function of a half adder is to add two binary numbers without carrying, making it a fundamental building block in digital circuits.

What does the 'C in' input represent in a full adder?

• The carry bit from the previous addition

• The sum of A and B

• The reset signal

• The output digit

Answer explanation

The 'C in' input in a full adder represents the carry bit from the previous addition, allowing for the addition of multiple binary numbers.

What is the purpose of connecting multiple full adders together?

• To perform subtraction

• To convert binary to decimal

• To decrease calculation time

• To add binary numbers of n bits together

Answer explanation

Connecting multiple full adders together is done to add binary numbers of n bits together, allowing for the addition of larger binary numbers by breaking them down into smaller components.

What is the name given to the circuit that combines multiple full adders?

• Ripple carry adder

• Parallel adder

• Serial adder

• Sequential adder

Answer explanation

The name given to the circuit that combines multiple full adders is a Ripple carry adder, which is used to perform addition of multiple bits in parallel.

What is the role of an OR gate in a full adder circuit?

• To determine the carry output

• To reset the circuit

• To determine the sum output

• To provide additional inputs

Answer explanation

The role of an OR gate in a full adder circuit is to determine the carry output.