ALU 101 Data Representation and Number Systems

Question 1

How is the decimal number 25 represented in 8-bit binary?

Accepted Answer

00011001

Answer

25 = 16 + 8 + 1 = 2^4 + 2^3 + 2^0, giving the 8-bit pattern 00011001.

Question 2

In two's complement representation, what is the value of the 8-bit pattern 11110000?

Accepted Answer

-16

Answer

Inverting 11110000 gives 00001111 = 15, then adding 1 gives 16, so the value is -16.

Question 3

What is the hexadecimal equivalent of the binary number 10110101?

Accepted Answer

B5

Answer

Splitting into nibbles: 1011 = B and 0101 = 5, giving 0xB5.

Question 4

Which number representation allows the ALU to perform subtraction using only adder hardware?

Accepted Answer

Two's complement

Answer

Two's complement lets you subtract by adding the negated value, so no separate subtractor circuit is needed.

Question 5

In BCD (Binary Coded Decimal), how is the decimal digit 7 encoded?

Accepted Answer

0111

Answer

BCD encodes each decimal digit in 4 bits exactly as its standard binary equivalent, so 7 = 0111.

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test