ALU 101 Overflow and Error Handling 2

Question 1

What causes a divide-by-zero exception in an ALU?

Accepted Answer

The divisor operand equals zero, making the quotient mathematically undefined

Answer

Division by zero is undefined mathematically; the ALU detects a zero divisor and raises an exception rather than producing an infinite or garbage result.

Question 2

In IEEE 754 floating-point, what value does the FPU produce for a division by zero operation?

Accepted Answer

Positive or negative infinity

Answer

IEEE 754 defines that a finite non-zero number divided by zero yields ±infinity, with the sign determined by the operand signs.

Question 3

What is a NaN (Not a Number) result in floating-point ALU operations?

Accepted Answer

A special bit pattern indicating an undefined or unrepresentable result such as 0/0 or sqrt(-1)

Answer

NaN is produced by operations with no valid numeric result, such as 0.0/0.0 or the square root of a negative number, and propagates through subsequent computations.

Question 4

What does 'silent NaN' vs 'signaling NaN' mean in IEEE 754?

Accepted Answer

Signaling NaN raises a floating-point exception when used; quiet NaN propagates silently

Answer

A signaling NaN (sNaN) raises an invalid operation exception if used in a computation; a quiet NaN (qNaN) propagates through operations without raising exceptions.

Question 5

How does the ALU detect and flag an underflow condition in floating-point arithmetic?

Accepted Answer

When the result is too small to be represented as a normalized number

Answer

Underflow occurs when the magnitude of the result is smaller than the smallest normalized floating-point number, causing precision loss or a flush to zero.

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test

ALU 101 Overflow and Error Handling 2