ALU 101 Data Representation and Number Systems 3

Question 1

Adding 0111 + 0001 in 4-bit two's complement produces which result and flag?

Accepted Answer

1000, Overflow set

Answer

0111 (7) + 0001 (1) = 1000 in 4 bits; since two positive numbers produced a negative result, the overflow flag is set.

Question 2

What does the term 'word size' define in the context of an ALU?

Accepted Answer

The number of bits the ALU processes in a single operation

Answer

Word size is the number of bits an ALU handles as a single unit, determining the maximum integer precision per operation.

Question 3

Which representation is used internally by modern ALUs for signed integer arithmetic?

Accepted Answer

Two's complement

Answer

Two's complement is universal in modern ALUs because addition, subtraction, and negation all work with the same hardware without special cases.

Question 4

What is the decimal value of the 8-bit two's complement number 10000000?

Accepted Answer

-128

Answer

In 8-bit two's complement, 10000000 represents -128, the most negative representable value.

Question 5

How does an ALU typically represent the number zero in two's complement?

Accepted Answer

As a single unique pattern of all zeros

Answer

Two's complement has exactly one representation of zero: all bits equal to 0, unlike one's complement which has two.

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test