ALU 101 Overflow and Error Handling

Question 1

What is integer overflow in the context of ALU operations?

Accepted Answer

When an arithmetic result exceeds the maximum value that can be stored in the destination register

Answer

When an operand is too small for the ALU

Answer

When the clock frequency is too high

Answer

When the carry flag is not set

Question 2

In two's complement addition, how can you detect signed overflow using the carry-in and carry-out of the MSB?

Accepted Answer

Overflow = carry-in XOR carry-out of the MSB

Answer

Overflow = carry-in AND carry-out

Answer

Overflow = NOT carry-out

Answer

Overflow = carry-in OR carry-out

Question 3

What distinguishes unsigned overflow (carry) from signed overflow in ALU results?

Accepted Answer

Unsigned overflow (CF) means the result exceeded the unsigned range; signed overflow (OF) means it exceeded the two's complement range

Answer

They are the same condition

Answer

Unsigned overflow only occurs in subtraction

Answer

Signed overflow sets the carry flag

Question 4

What happens in most hardware ALUs when integer overflow is not handled explicitly?

Accepted Answer

The result wraps around modulo 2^n, potentially producing an incorrect silent error

Answer

The CPU halts immediately

Answer

The overflow is automatically corrected

Answer

The instruction is retried

Question 5

Which programming practice helps prevent integer overflow errors when using ALU results in software?

Accepted Answer

Checking operand ranges before the operation or using overflow-checking arithmetic libraries

Answer

Using only unsigned integers

Answer

Increasing the clock speed

Answer

Storing results in floating-point registers

Question 6

What is an arithmetic exception trap in the context of ALU error handling?

Accepted Answer

A hardware interrupt triggered when the ALU detects an error condition such as overflow or division by zero

Answer

A software subroutine that performs division

Answer

A pipeline flush for branch misprediction

Answer

A memory access fault